Hearing assistance device with a low-power mode

Abstract

A portable hearing assistance device comprises an input unit, an output unit, a forward path between the input unit and the output unit, and an energy source for energizing components of the hearing assistance device. The hearing assistance device further comprises a control unit to control activation (or deactivation) of a low-power mode of operation of the hearing assistance device. When the low-power mode is activated—the draw of current from said energy source is reduced compared to a normal mode of operation of the device, the activation (or deactivation) being influenced by a combination of at least two different control input signals to the control unit, each control input signal being a signal selected from 1) signals relating to current physical environment, 2) signals relating to current acoustic environment, 3) signals relating to current wearer state, and 4) signals relating to current state or operation mode.

Claims

1. A hearing assistance system including a portable hearing assistance device, the portable hearing assistance device comprising: an input unit for providing an electric input signal comprising an audio signal; an output unit for providing on output signal originating from the audio signal; a forward path between the input unit and the output unit; an energy source for energizing components of the hearing assistance device; wherein when a low-power mode of operation of the hearing assistance device is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the device, the activation being influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein a deactivation of the low-power mode is also controlled, and the number of control input signals used to decide on a deactivation of the low-power mode is smaller than the number of control input signals used to activate the low-power mode.

2. The hearing assistance system according to claim 1, wherein one or more of said control input signals is/are received from another device.

3. The hearing assistance system according to claim 1, wherein said at least two different control input signals are selected from at least two different of said types of signals 1), 2), 3) or 4).

4. The hearing assistance system according to claim 1, wherein the at least two control input signals are dynamically selected, among a larger number of control input signals, that influence the decision on activation of a low-power mode at a given point in time depending on the classification of the current situation.

5. The hearing assistance system according to claim 1, wherein at least one of the control input signals for deciding on a deactivation of the low-power mode is different from the control input signals used to decide on an activation of the low-power mode.

6. The hearing assistance system according to claim 1, wherein deactivation of the low-power mode with a predefined time period after a condition for leaving the low-power mode has been fulfilled.

7. A hearing assistance system according to claim 1, wherein the hearing assistance system comprises a hearing aid.

8. A hearing assistance system including a portable hearing assistance device, the portable assistance device comprising: an input unit for providing an electric input signal comprising an audio signal; an output unit for providing on output signal originating from the audio signal; a forward path between the input unit and the output unit; an energy source for energizing components of the hearing assistance device; wherein when a low-power mode of operation of the hearing assistance device is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the device, the activation being influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein the hearing assistance system comprises a user operable activation element configured to allow deactivation of the low-power mode.

9. The hearing assistance system according to claim 8, configured to provide that an automatic decision to enter the low-power mode is disabled for a predefined time after an operation of the manual activation element to deactivate the low-power mode has been performed.

10. A hearing assistance system according to claim 8, wherein the hearing assistance system comprises a hearing aid.

11. A hearing assistance system including a portable hearing assistance device, the portable assistance device comprising: an input unit for providing an electric input signal comprising an audio signal; an output unit for providing on output signal originating from the audio signal; a forward path between the input unit and the output unit; an energy source for energizing components of the hearing assistance device; wherein when a low-power mode of operation of the hearing assistance device is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the device, the activation being influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, said hearing assistance system further including: an auxiliary device, the system being adapted to establish a communication link between the portable hearing assistance device and the auxiliary device to provide that information signals can be exchanged between or forwarded from one to the other.

12. The hearing assistance system according to claim 11, wherein the auxiliary device comprises an audio gateway device.

13. The hearing assistance system according to claim 11, wherein the auxiliary device comprises a user interface adapted to allow a user to add and/or configure a particular external sensor to provide a control input signal.

14. The hearing assistance system according to claim 11, wherein the auxiliary device comprises a user interface adapted to allow a user to deactivate a particular external sensor to provide a control input signal.

15. The hearing assistance system according to claim 11, wherein the auxiliary device comprises another hearing assistance device, and the two hearing assistance devices form part of a binaural hearing assistance system.

16. The hearing assistance system according to claim 15, wherein the two hearing assistance devices of the binaural hearing assistance system are adapted to exchange at least one of their respective corresponding control input signals, and to compare their respective corresponding control input signals, and to use the result thereof as an input to controlling the activation of said low-power mode of operation of the hearing assistance device.

17. A hearing assistance system according to claim 11, wherein the hearing assistance system comprises a hearing aid.

18. A hearing assistance system according to claim 11, wherein the auxiliary devices comprises a remote control device for controlling functionality and operation of the hearing assistance device, an audio delivery device, a telephone apparatus, or a PC or a combination thereof.

19. A method of providing a low-power mode in a portable hearing assistance device, the portable hearing assistance device comprising an input unit for providing an electric input signal comprising an audio signal, an output unit for providing an output signal originating from the audio signal, a forward path between the input unit and the output unit, and an energy source for energizing components of the hearing assistance device, the method comprising: providing a low-power mode and a normal mode of operation of the hearing assistance device, wherein when said low-power mode is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the hearing assistance device; controlling the activation of said low-power mode of operation of the hearing assistance device by providing that the activation is influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein a deactivation of the low-power mode is also controlled by the controlling step, and the number of control input signals used by the controlling step to decide on a deactivation of the low-power mode is smaller than the number of control input signals used to activate the low-power mode.

20. A portable hearing assistance device comprising an input unit for providing an electric input signal comprising an audio signal, an output unit for providing on output signal originating from the audio signal, a forward path between the input unit and the output unit, an energy source for energizing components of the hearing assistance device, wherein, when a low-power mode of operation of the hearing assistance device is activated, the draw of current from said energy source is reduced compared to a normal mode of operation of the device, the activation being influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein the number of control input signals used to decide on a deactivation of the low-power mode is smaller than the number of control input signals used to activate the low-power mode.

21. A portable hearing assistance device according to claim 20 wherein deactivation of the low-power mode is controlled by a control input signal from a movement sensor.

22. A portable hearing assistance device according to claim 21 wherein one or more additional sensors providing one or more additional control input signals, which in a low-power mode is/are initially deactivated, is/are activated when a first control input signal indicates that a deactivation of the low-power mode should be initiated.

23. A method of providing a low-power mode in a portable hearing assistance device, the portable hearing assistance device comprising an input unit for providing an electric input signal comprising an audio signal, an output unit for providing an output signal originating from the audio signal, a forward path between the input unit and the output unit, and an energy source for energizing components of the hearing assistance device, the method comprising: providing a low-power mode and a normal mode of operation of the hearing assistance device, wherein when said low-power mode is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the hearing assistance device; controlling the activation of said low-power mode of operation of the hearing assistance device by providing that the activation is influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein said method further comprises enabling deactivation of the low-power mode via a user operable activation element.

24. A method of providing a low-power mode in a portable hearing assistance device, the portable hearing assistance device comprising an input unit for providing an electric input signal comprising an audio signal, an output unit for providing an output signal originating from the audio signal, a forward path between the input unit and the output unit, and an energy source for energizing components of the hearing assistance device, the method comprising: providing a low-power mode and a normal mode of operation of the hearing assistance device, wherein when said low-power mode is activated the draw of current from said energy source is reduced compared to a normal mode of operation of the hearing assistance device; controlling the activation of said low-power mode of operation of the hearing assistance device by providing that the activation is influenced by a combination of at least two different control input signals, each control input signal being a signal selected from the group of signals comprising 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device, wherein said method further establishes a communication link between the portable hearing assistance device and an auxiliary device to provide that information signals can be exchanged between or forwarded from one to the other.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The disclosure will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

(2) FIG. 1 shows a first embodiment of a hearing assistance device according to the present disclosure (FIG. 1a) and an example of a corresponding combination of control inputs providing a resulting output from the control unit to govern the switching of the hearing assistance device between a normal mode and a low-power mode of operation (FIG. 1b),

(3) FIG. 2 shows an embodiment of a hearing assistance system comprising a hearing assistance device and an auxiliary device, here an audio gateway device or a telephone, and a number of external sensors, the system being adapted for establishing communication links between at least some of the devices,

(4) FIG. 3 shows an embodiment of a binaural hearing aid system comprising first and second hearing instruments,

(5) FIG. 4 shows a second embodiment of a hearing assistance device according to the present disclosure,

(6) FIG. 5 shows an embodiment of a control unit for a hearing assistance device according to the present disclosure,

(7) FIG. 6 shows first (FIG. 6a) and second (FIG. 6b) use scenarios for a binaural hearing assistance system according to the present disclosure and examples of feedback path gains for three different situations (FIG. 6c),

(8) FIG. 7 shows an embodiment of a hearing assistance device with corresponding user interface in a remote control, here a Smartphone,

(9) FIG. 8 shows an embodiment of a hearing assistance device according to the present disclosure wherein the power distribution is schematically illustrated,

(10) FIG. 9 shows an exemplary embodiment of a hearing assistance device comprising a skin resistance sensor and allowing a control unit to receive power in a low-power mode, and

(11) FIG. 10 shows switch which can be used to implement a low-power mode in a hearing assistance device, e.g. to turn off power to all parts of the device.

(12) The figures are schematic and simplified for clarity, and they just show details which are essential to the understanding of the disclosure, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts.

(13) Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only. Other embodiments may become apparent to those skilled in the art from the following detailed description.

DETAILED DESCRIPTION OF EMBODIMENTS

(14) FIG. 1 shows a first embodiment of a hearing assistance device according to the present disclosure (FIG. 1a) and an example of a corresponding combination of control inputs providing a resulting output from the control unit to govern the switching of the hearing assistance device between a normal mode and a low-power mode of operation (FIG. 1b). FIG. 1a shows a portable hearing assistance device (HA) comprising an input transducer (MIC, here a microphone, also referred to herein as an “input unit”), an output transducer (SPK, here a loudspeaker, also referred to herein as an “output unit”), and a forward path between the input transducer and the output transducer, the forward path comprising a signal processing unit (SPU). The hearing assistance device further comprises an energy source (BAT, e.g. a battery) for energizing components of the hearing assistance device (including the input and output transducers and the signal processing unit). The hearing assistance device further comprises a control unit (DET-CTR) configured to control at least the activation (and possibly additionally the deactivation) of a low-power mode of operation of the hearing assistance device based on a number of control inputs ID1, ID2, ID3, and ID4 from detectors DET1, DET2, DET3, and DET4 (FBE), respectively. The low-power mode (wherein the draw of current from the energy source (BAT) is reduced compared to a normal mode of operation of the device) is implemented by a switch unit (SW) configured to (individually or simultaneously) enable of disable the power supply to selected functional blocks (or groups of blocks) of the hearing assistance device, e.g. including the signal processing unit (or at least a part thereof), cf. signals Power to units. The switch unit (SW) is controlled by a control signal BATC from the control unit (DET-CTR). The control signal BATC for influencing the activation (and possibly the deactivation) of a low-power mode (involving powering down or up, respectively, of selected functional blocks) of the hearing assistance device is generated based on two or more of the control input signals ID1, ID2, ID3, and ID4 to the control unit. The control input signals ID1, ID2, ID3, and ID4 are selected from the group of signals comprising

(15) 1) signals relating to a current physical environment of the hearing assistance device, 2) signals relating to a current acoustic environment of the hearing assistance device, 3) signals relating to a current state of a wearer of the hearing assistance device, and 4) signals relating to a current state or mode of operation of the hearing assistance device and/or of another device in communication with the hearing assistance device.

(16) The signal processing unit (SPU) is preferably configured for applying a frequency dependent gain to the signal p(n) provided by the input transducer (MIC) (or rather a signal e(n) originating there from) and for providing an enhanced signal u(n) to the output transducer (SPK). The index n represents a time index. The signals may be processed in the time domain (in which case n may be a sample index) or in the frequency domain (in which case n may be a time frame index). In an embodiment, the hearing assistance device comprises a hearing aid, wherein the frequency dependent gain applied by the signal processing unit is adapted to a user's hearing impairment. The hearing assistance device further comprises a feedback cancellation system (feedback estimation unit FBE (also denoted detector DET4) and sum-unit ‘+’) for estimating and reducing (or preferably cancelling) acoustic feedback from an ‘external’ feedback path (FB) from the output to the input transducer of the hearing assistance device. The feedback estimation unit FBE comprises an adaptive filter comprising a variable filter part (Filter in FIG. 1a), which is controlled by a prediction error algorithm (Algorithm in FIG. 1a), e.g. an LMS (Least Means Squared) algorithm, in order to predict and cancel the part of the microphone signal p(n) that is caused by feedback from the loudspeaker (SPK) of the hearing assistance device. The prediction error algorithm (Algorithm) uses a reference signal (here the output signal u(n)) together with a signal originating from the microphone signal (here the so-called ‘error signal’ e(n)) to find the setting (filter coefficients) of the variable filter (Filter) that minimizes the prediction error when the reference signal u(n) is applied to the adaptive filter. The estimate vh(n) of the feedback path provided by the adaptive filter is subtracted from the microphone signal p(n) in sum unit ‘+’ providing the error (or feedback-corrected) signal e(n), which is fed to the signal processing unit (SPU) and to the algorithm part (Algorithm) of the adaptive filter.

(17) The detectors DET1, DET2, DET3, and DET4 (FBE) may e.g. include sensors providing signals from the four types of signals 1), 2), 3), 4) mentioned above. In an embodiment, DET1 is a sensor providing signals relating to a current physical environment of the hearing assistance device. DET1 may e.g. comprise a movement sensor, e.g. an acceleration sensor for detecting a linear acceleration of the hearing assistance device and/or a gyroscope sensor for detecting a rotational acceleration of the hearing assistance device. Such sensors are e.g. available from Bosch (cf. e.g. MEMS sensor BMX055, comprising both). In an embodiment, DET2 is a sensor providing signals relating to a current acoustic environment of the hearing assistance device. DET2 may e.g. comprise a level detector, a voice activity detector, and/or a wind noise detector. In an embodiment, DET3 is a sensor providing signals relating to a current state of a wearer of the hearing assistance device. In an embodiment, DET3 comprises a temperature sensor for monitoring a temperature of the local environment of the hearing assistance device (e.g. the skin temperature of a user of the hearing assistance device, when the hearing assistance device is worn by the user in a normal, operational position). Alternatively, DET3 comprises electrodes for measuring brain waves of the user (when the hearing assistance device is being worn in a normal, operational position). In an embodiment, DET4 is a sensor providing signals relating to a current state or mode of operation of the hearing assistance device. In an embodiment (as shown in FIG. 1a), DET4 comprises a feedback estimation unit (FBE) providing an estimate (signal ID4/vh(n)) of a current feedback from the output transducer (SPK) to an input transducer (MIC).

(18) The control unit (DET-CTR) is configured to control the activation (and possibly deactivation) of a low-power mode of operation of the hearing assistance device, based on a (e.g. logic or predefined, e.g. tabulated) combination of the four control inputs ID1, ID2, ID3, and ID4. FIG. 1b provides an example of a (tabulated) combination of the control input signals ID1, ID2, ID3, and ID4 to provide a reliable decision (via control signal BATC to the switch unit (SW)) to activate (and possibly deactivate) a low-power mode of the hearing assistance device. In the example of FIG. 1b, the control input signals are assumed to take on binary values (e.g. 0 or 1, or as here ‘state values’). Detector 1 (DET1) providing control input signal ID1 is assumed to comprise a movement detector configured to indicate whether the hearing assistance device is in movement (ID1=MOVE) or not (ID1=STILL). Detector 2 (DET2) providing control input signal ID2 is assumed to comprise a voice activity detector configured to indicate whether the acoustic environment of the hearing assistance device (as extracted from the input signal p(n) of the microphone) comprises a voice (e.g. speech) (ID2=VOICE) or not (ID2=NO VOICE). Detector 3 (DET3) providing control input signal ID3 is assumed to comprise a temperature sensor configured to indicate whether the temperature in the immediate vicinity of the hearing assistance device is above (ID3=T≧T.sub.th) or below (ID3=T<T.sub.th) a reference temperature T.sub.th (exemplified by 35° C. in FIG. 1b). Detector 4 (DET4) providing control input signal ID4 is assumed to comprise feedback estimation unit configured to indicate whether the current feedback (e.g. represented by a feedback measure) in the hearing assistance device is above (ID4=FB≧X.sub.th) or below (ID4=FB<X.sub.th) a reference feedback value X.sub.th. The 16 possible combinations of the 4 binary input signals are provided and the resulting output signal (BATC) from the control unit to the switch unit (SW) is indicated for each of the 16 combinations. The resulting output signal (BATC) is indicated as NORM and as LP, in case a normal mode of operation and a low-power mode of operation, respectively, is assumed to be the more relevant for the given combination of control input signals. The column ‘Comment’ indicates for each combination of input signals to and resulting output signal from the control unit a possible situation. For each input signal ID1-ID4 one of its binary values is taken to indicate a situation where the hearing assistance device is assumed to be worn (white background, e.g. ID3=T≧35° C.), the other that it is assumed NOT to be worn (grey background, e.g. ID3=T<35° C.). For some of the combinations of the input signal values, no completely un-ambiguous conclusion can be drawn. The strategy applied in FIG. 1b for arriving at an output signal value of BATC=LP has been to require that a majority (here at least three) of the input signal values to ‘imply’ a situation where the hearing aid is not being worn (i.e. at least 3 fields have a grey background). The reason behind this strategy is to minimize the risk of powering the hearing assistance device in situations where it should not be powered down. Of course this may be at the risk of NOT powering the hearing assistance device down in some cases where it preferably should have been. In a preferred embodiment, a control input signal from an environment temperature sensor (e.g. from an external device, e.g. a wireless thermometer or a Smartphone, cf. FIG. 2) is provided to the control unit to complement the ‘body temperature’ sensor (DET3 in FIG. 1). Thereby a more safe conclusion regarding whether or not the hearing assistance device is in contact with the body of a user can be made.

(19) FIG. 2 shows an embodiment of a hearing assistance system comprising a hearing assistance device and an auxiliary device, here an audio gateway device or a telephone, and a number of external sensors, the system being adapted for establishing communication links between at least some of the devices. The hearing assistance system comprises a hearing assistance device HA and an auxiliary device AuxD. The auxiliary device AuxD is shown to comprise an audio gateway device adapted for receiving a multitude of audio signals (here shown from a telephone apparatus, e.g. a wireless telephone TEL (e.g. a Smartphone having access to a data network, e.g. the Internet), an entertainment device (here a Music player). Additionally, the auxiliary device is adapted to receive a signal from a sensor device xSens and to transfer it to the hearing assistance device.

(20) The auxiliary device AuxD comprises a microphone (AD-MIC) for picking up sounds from the environment, e.g. a voice (OV) of the user (U) wearing the portable hearing assistance system (or of another person in the environment). In the embodiment of FIG. 2, the auxiliary device AuxD is adapted for connecting the microphone (AD-MIC) to one or more of the external audio sources (including the telephone TEL) via wireless links WLB, here in the form of digital transmission links according to the Bluetooth standard as indicated by the Bluetooth transceiver (BT-Tx-Rx) in the auxiliary device AuxD. The audio sources and the auxiliary device may be paired prior to the establishment of a wireless link between them using the button BT-pair on the auxiliary device. The wireless links WLB may alternatively be implemented in any other convenient wireless and/or wired manner, and according to any appropriate modulation type or transmission standard, possibly different for different audio sources. The intended mode of operation of the hearing assistance system (incl. the selection of the audio source) can be selected by the user via mode selection buttons Mode1 and Mode2. The auxiliary device AuxD may further have the function of a remote control of the hearing assistance device, e.g. for changing program or operating parameters (e.g. volume, cf. Vol-button) in the hearing assistance device.

(21) The hearing assistance device HA is shown as a device mounted at the ear of a user U. The hearing assistance device may be a hearing assistance device as discussed in connection with FIG. 1 and e.g. comprise a microphone for picking up a sound signal IS (e.g. comprising a speech and/or a noise signal) in the environment of the hearing assistance device. The hearing assistance device HA of the embodiment of FIG. 2 additionally comprises a wireless transceiver, here indicated to be based on inductive communication (I-Rx). The transceiver (at least) comprises an inductive receiver (i.e. an inductive coil, which is inductively coupled to a corresponding coil in a transceiver (I-Tx) of the auxiliary device AuxD), which is adapted to receive the audio signal from the auxiliary device (either as a baseband signal or as a modulated (analogue or digital) signal, and in the latter case to extract the audio signal from the modulated signal). The inductive link WLI between the auxiliary device and the hearing assistance device is indicated to be one-way, but may alternatively be two-way (e.g. to be able to exchange control signals between (mainly) transmitting AuxD and receiving HA device, e.g. to agree on an appropriate transmission channel). Alternatively or additionally, the hearing assistance device (and/or the auxiliary device) may be adapted to receive an audio and/or an information signal directly from a telephone (e.g. a Smartphone) as e.g. indicated by the dotted arrow (WLB) between the telephone apparatus (TEL) and the hearing assistance device (HA) and the additional Bluetooth transceiver indicated by BT in the hearing assistance device HA. In an embodiment, the telephone apparatus and the hearing assistance device are configured to allow the direct link between them to be based on the Bluetooth-Low Energy (BT-LE) standard. In such scenario, the telephone apparatus may be viewed as the auxiliary device of the hearing assistance system (instead of or in addition to the audio gateway device). In the example of FIG. 2, the telephone apparatus is assumed to have access to a network, e.g. the Internet, and/or to comprise one or more sensors, e.g. a temperature sensor, a location sensor, a movement sensor, etc. One or more signals from such sensors are assumed to be transmitted (or transferable) to the hearing assistance device HA either directly (via link WLB) or via the (intermediate) auxiliary device AuxD (and link WLI). In FIG. 2, the environmental temperature T=41° C. shown on the display of the Smartphone (TEL) is transferred to the hearing assistance device and used as a control input signal to the control unit.

(22) The sensor device xSens is wirelessly connected to the hearing assistance device HA via the auxiliary device AuxD. The wireless link between the external sensor xSens and the auxiliary device AuxD may preferably be based on the BT-LE standard. In an embodiment, the link from the external sensor xSens is a direct link to the hearing assistance device HA (e.g. according to BT-LE). In an embodiment, the external sensor device xSens is a sensor of the temperature of the environment (e.g. a room) of the hearing assistance device.

(23) The auxiliary device AuxD is shown to be carried around the neck of the user U in a neck-strap NSt. Alternatively, the auxiliary device may be carried in other ways, e.g. in the hand, in a pocket, clipped on clothing, etc.

(24) FIG. 3 shows an embodiment of a binaural hearing aid system comprising first and second hearing instruments. The binaural hearing aid system comprises first and second hearing instruments (HI-1, HI-2) adapted for being located at or in left and right ears of a user.

(25) The hearing instruments HI-1 and HI-2 each comprise a time to time-frequency conversion unit (IU) for converting time domain input signals INm and INw to time-frequency input signals IFB.sub.1, IFB.sub.2, . . . , IFB.sub.N allowing processing in the respective signal processing units (SPU) in a number of frequency channels FB.sub.1, FB.sub.2, . . . , FB.sub.N. Each hearing instrument comprises a microphone unit comprising microphone (MIC) and analogue to digital conversion unit (AD) providing digitized input microphone signal INm, as well as a wireless transceiver comprising antenna (ANT) and transceiver circuitry (Rx/Tx) providing digitized input wireless signal INw. The input unit IU is configured to select one of the input signals INm or INw (or a mixture of them) and provide it as band split signal (IFB.sub.1:IFB.sub.N). The hearing instruments HI-1 and HI-2 each further comprise a time-frequency to time conversion unit (OU) for converting processed output signals OFB.sub.1, OFB.sub.2, . . . , OFB.sub.N to time domain signals OUT, which is fed to digital to analogue transformation unit DA and on to the output transducer, here a loudspeaker (SP).

(26) The hearing instruments of FIG. 3 are further adapted for exchanging information between them via a wireless communication link, e.g. a specific inter-aural (IA) wireless link (IA-WLS). The inter-aural link may e.g. be based on inductive (near-field) communication, or alternatively on radiated field (far-field) communication. The two hearing instruments HI-1, HI-2 are adapted to allow the exchange of status signals, e.g. including the transmission of detector signals generated or received by an instrument at a particular ear to the instrument at the other ear. To establish the inter-aural link, each hearing instrument comprises antenna and transceiver circuitry (here indicated by block IA-Rx/Tx). Each hearing instrument HI-1 and HI-2 is an embodiment of a hearing assistance devise as described in the present application and may e.g. comprise some or all of the functional elements described in connection with FIG. 1. Each of the instruments HI-1 and HI-2 of the binaural hearing aid system of FIG. 3 comprises a control unit DET-CTR for—via control signal BATC—controlling the distribution of power from the battery BAT to various parts of the respective hearing instrument. The control unit DET-CTR receives control input signals ID1 from a first detector unit (DET1), and ID2 from the signal processing unit SPU both originating from the hearing instrument in question (e.g. HI-1) and a control signal input XD1 corresponding to ID1 generated by the first detector (DET1) from the other hearing instrument (e.g. HI-2) (and vice versa). The control signals ID1, XD1 from the local (ID1) and the opposite (XD1) device, respectively, are e.g. used together to influence a decision regarding entering a low-power mode in the local device (e.g. HI-1). In an embodiment, the hearing assistance system further comprises an auxiliary device for transmitting an audio signal to the hearing instruments. In an embodiment, the hearing assistance system is adapted to provide that a telephone input signal can be received in the hearing assistance device(s) via the auxiliary device or directly from the telephone. The first detector DET1 receives time domain input signals INm and INw and provides control input signal ID1. In an embodiment, control input signal ID1 is indicative of the acoustic environment (based on microphone input signal INm). In an embodiment, control input signal ID1 is indicative of the current reception of an audio signal (e.g. audio streaming). In an embodiment, control input signal ID1 is indicative of the hearing instrument being currently in operational use, if either an audio signal is being received by the wireless transceiver (signal INw comprises an audio signal) or if the microphone signal INm comprises a voiced signal (e.g. speech, e.g. comprising time segments having a modulation index above a certain threshold value). In an embodiment, the control input signals ID1 of the respective hearing instruments are compared, and if both comprise an audio signal (INw) or a voiced signal (INm), it is a good indication that the hearing instruments are in operational use (and that a low-power mode should not be entered). In an embodiment, control input signal ID2 generated in the signal processing unit is representative of at least one (optionally processed) signal of a particular frequency band, e.g. such frequency band comprising a tone (e.g. identified as a howl resulting from feedback). Such signal indicative of howl would—in the absence of an audio signal (INw) or a voiced signal (INm)—be indicative of the hearing instrument being in a non-operational state (e.g. located on a reflecting surface, e.g. a table, or in a storage box or other container or bag (without having its power turned off)). An appropriate action initiated by the control unit (DET-CTR) would be to ensure that the hearing instrument(s) would enter a low-power mode.

(27) FIG. 4 shows a second embodiment of a hearing assistance device according to the present disclosure. The hearing assistance device of FIG. 4, e.g. a hearing aid, comprises a forward path from an input transducer (here a microphone) (MIC) via a signal processing unit (SPU) to an output transducer (here a loudspeaker) (SPK). The signal processing unit (SPU) may e.g. be configured to apply a (time) and frequency dependent gain to the electric input signal IS1 provided by the microphone (MIC) and to provide an enhanced output signal IS2 fed to the loudspeaker (SPK). The hearing assistance device further comprises a control unit (DET-CTR) receiving a number of control input signals ID1, ID2, ID3, ID4, XD1, and XD2 based on which a resulting control output signal BATC is generated and used to control the distribution of power to the hearing assistance device from a energy source (BAT), including the possible activation of a low-power mode of operation of the hearing assistance device. Control input signals ID1, ID2, ID3 and ID4 have their origin from detectors (FSD, MFD, XCOR and FBE) of the hearing assistance device itself, whereas control input signals XD1 and XD2, have their origin from detectors external to the hearing assistance device (e.g. wirelessly received, from an auxiliary device, e.g. from the detector directly or from or via a remote control of the hearing assistance device, e.g. a Smartphone). Control input signal ID1 is generated by a detector (FSD) of the strength of a (possibly varying) electromagnetic field. Such signal can e.g. indicate whether or not the hearing assistance device is in an environment comprising significant amounts of electromagnetic signals, such significant amounts being for example (but not necessarily) due to the close presence of a telephone apparatus or of a contra-lateral hearing assistance device of a binaural hearing assistance system (e.g. a binaural hearing aid system), the two situations being possibly differentiated by different threshold field strengths. No or small amounts may indicate that a possible partner device (or other communication devices producing electromagnetic interference) is not present or powered down. Control input signal ID2 is generated by a detector (MFD) of the strength of a static magnetic field. Such signal can e.g. indicate whether or not the hearing assistance device is located in proximity to a permanent magnet, e.g. located in a telephone apparatus and indicating a telephone mode (implying no activation of a low-power mode) or e.g. located in a storage box, indicating a non-operational state (implying activation of a low-power mode). Control input signal ID3 is generated by a detector (XCOR) of correlation (e.g. the cross-correlation) of two signals IS1, IS2 of (here before and after the signal processing unit) the forward path of the hearing assistance device. Such signal can e.g. indicate a quality of a current feedback estimate (and thus contribute to an appropriate weight of a feedback estimate to a decision concerning entering a low-power mode of operation in a given situation). Control input signal ID4 is generated by a detector (FBE) for estimating a feedback path from the output transducer (SPK) to the input transducer (MIC). A large value of the feedback path at certain frequencies may indicate that the hearing assistance device is removed from its operational position at the ear and e.g. located at a table or in a storage box (or held in a hand) (implying activation of a low-power mode). Otherwise it may indicate a ‘true’ feedback situation during operation, e.g. resting an ear with the hearing assistance device at a pillow, putting on a hat, putting a hand to the hearing assistance device, hugging a person, etc. (implying no activation of a low-power mode). Such situations may be possibly be differentiated by comparing a currently measured feedback path with different stored typical frequency dependent feedback paths (cf. e.g. FIG. 6c) and/or with the aid of additional control input signals from other detectors (cf. e.g. FIG. 1 and description thereof). Control input signals XD1 and XD2 (e.g. wirelessly) received from external devices may e.g. include an external temperature, a location information, or other information signal (e.g. from a remote control, a telephone, or a contra-lateral hearing assistance device of a binaural hearing assistance system).

(28) FIG. 5 shows an embodiment of a control unit for a hearing assistance device according to the present disclosure. The control unit (DET-CTR) comprises a classification unit (CLASSIFICATION) configured to classify the current situation based on a multitude of control input signals (ID.sub.1, ID.sub.2, . . . , ID.sub.N from internal detectors and XD.sub.1, XD.sub.2, . . . , XD.sub.M from external detectors). The classification unit is configured to provide that the control input signals that—in a given ‘current situation’—are used as the two or more control input signals (D.sub.1, D.sub.2, . . . , D.sub.Q) to the part of the control unit (CONTROL) that decides on activation or deactivation of a low-power mode (via output signal BATC) are signals from detectors that represent parameters or properties that complement each other in the current situation. The classification unit (CLASSIFICATION) provides the control input signals (D.sub.1, D.sub.2, . . . , D.sub.Q) to be used in a current situation by controlling a switch array (SWITCH) receiving all control input signals (ID.sub.1, ID.sub.2, . . . ID.sub.N and XD.sub.1, XD.sub.2, . . . , XD.sub.M) and a control signal CL from the classification unit for individually setting the switches of the switch array. A scheme for selecting the control inputs (D.sub.1, D.sub.2, . . . , D.sub.Q) in a given situation may depend on the current values of one or more of the control input signals (ID.sub.1, ID.sub.2, . . . , ID.sub.N and XD.sub.1, XD.sub.2, . . . , XD.sub.M). Alternatively or additionally, the control inputs (D.sub.1, D.sub.2, . . . , D.sub.Q) in a given situation may be configurable, e.g. by an audiologist in a fitting situation and/or by a user (cf. also FIG. 7), to thereby allow the hearing assistance device to be configured to the habits and wishes of the user in question (with a view to ensuring a safe criterion for deciding to enter a low-power mode of operation).

(29) FIG. 6 shows first (FIG. 6a) and second (FIG. 6b) use scenarios for a binaural hearing assistance system according to the present disclosure and examples of feedback path gains for three different situations (FIG. 6c). The use scenarios of FIGS. 6a and 6b both illustrate a hearing assistance system (e.g. a binaural hearing aid system) comprising first and second hearing assistance devices (HA1, HA2) located in close vicinity of each other and assumed not to be located at the ears of a user, and not to be in a low-power mode. Each hearing assistance device (HA1, HA2) may be embodied in a hearing assistance device as described elsewhere in the present application (e.g. in FIG. 1, 3, 4). In the system of FIG. 6a, the hearing assistance devices (HA1, HA2) each comprise antenna and transceiver circuitry (Rx/Tx) configured to establish an inter-aural wireless link IA-WLS between the two hearing assistance devices (e.g. allowing an exchange of detector signals between the devices). Each hearing assistance device further comprises a temperature detector (TD) for sensing the temperature of the hearing assistance device (e.g. a skin temperature of the user, when the hearing assistance device in question is operationally mounted at an ear, or a temperature of the location of the hearing assistance device, when located elsewhere). A combination of a low temperature provided by the temperature detector (TD) and a high level of the received signal (either indicated by a field strength sensor or a saturated receiver or other measures) provided by monitoring the wireless transceiver (Rx/Tx) would indicate that the two hearing assistance devices are located close to each other and thus not worn. Based thereon a relatively safe decision to enter a low-power mode of operation for both hearing assistance devices can be made. In the scenario of FIG. 6b, the hearing assistance devices (HA1, HA2) are located on a reflecting surface (e.g. a table) TAB. Each hearing assistance device comprises a feedback detector for detecting a tone (or tones) due to a feedback signal (FEEDBACK HOWL) (and/or for estimating a feedback path) from the loudspeaker to the microphone of a given hearing assistance device. Each hearing assistance device further comprises a movement detector (MD) (e.g. an acceleration detector) for detecting a movement of the hearing assistance device in question. A combination of a detected howl from the feedback detector and a ‘no movement’ (or STILL, cf. FIG. 1b) detection from the movement detector (MD) would indicate that the two hearing assistance devices are not moved and located on a reflecting surface (thus implying a ‘not being worn’ situation). Based thereon a relatively safe decision to enter a low-power mode of operation for both hearing assistance devices can be made. The diagrams of FIG. 6c further illustrate the scenario of FIG. 6b. The graphs illustrate exemplary frequency dependent (0-10 kHz) feedback path gains (dB) for three different situations. For each situation, a feedback path from a loudspeaker to respective front (solid line) and rear (dotted line) microphones (e.g. located in a BTE part of the hearing assistance device) is shown. The left graph illustrates a normal feedback path where the hearing assistance device is located correctly at its operational position in a normal environment. The middle graph illustrates a feedback path where the hearing assistance device is located on a table (as in the scenario of FIG. 6b). The right graph illustrates a feedback path where the hearing assistance device is located in a storage box. The power estimate of the feedback increases from the ‘normal’ situation to the ‘table’ situation to the ‘storage box’ situation, as e.g. reflected in an appropriately chosen feedback measure (cf. e.g. ‘P’ below). The feedback estimate in a ‘normal’ situation has a dip at an intermediate frequency (in the example around 6.5 kHz), which is absent in the two other situations. The feedback path of the ‘table’ situation is clearly different from the ‘storage box’ situation at relatively low frequencies (below 2 kHz). The three feedback paths are thus clearly different, and a measured feedback path may be compared to such typical (stored) feedback paths and a ‘most likely’ situation identified by an appropriate comparison algorithm. The feedback path relating to a storage box is further peculiar in that it comprises frequency ranges with a gain larger than 1 (>0 dB). Offhand, one would believe such behavior to be impossible in a predominantly passive system, such as the acoustic feedback path. The occurrence may have its origin in reflections inside the cavity of the storage box that make the duration of the feedback path longer than the filter (e.g. a FIR filter) used to estimate the feedback path. If a longer filter were used for the feedback path estimation, we would most likely not see any parts of the feedback path having gains above 0 dB. With a view to identifying a feedback path relating to a ‘storage box’ (or ‘table’) situation, it is actually an advantage to have a (FIR) filter with a limited number of coefficients. If, however, a longer (FIR) filter is used, the estimated feedback path would contain energy at late reflections, which could be used to detect that the hearing aid was located inside a storage box. One feedback measure that may form a basis for such comparison is based on the power P of the feedback estimate FB, i.e.

(30) $P=\underset{n}{\overset{}{.Math.}}{.Math.\mathrm{FB}\left(n\right).Math.}^2$
or alternatively a frequency weighted power estimate

(31) $P=\underset{f}{\overset{}{.Math.}}w\left(f\right){.Math.\mathrm{FB}\left(f\right).Math.}^2$
where |FB(n)|.sup.2 and |FB(f)|.sup.2 are the squared absolute values of feedback gain at a particular time instant n and at a particular frequency f (and time), respectively, and w(f) is a frequency dependent weighting function. With reference to the feedback path graphs of FIG. 6c, the above power measure may e.g. be based on values FB(f.sub.i) at a number N.sub.f of frequencies f.sub.i, i=1, 2, . . . , N.sub.f, (e.g. at 0.5 kHz, 1 kHz, 2 kHz, 4 kHz, 6 kHz, 8 kHz), which are (repeatedly) stored in a memory of the hearing assistance device.

(32) FIG. 7 shows an embodiment of a hearing assistance device with corresponding user interface in a remote control, here a Smartphone. FIG. 7 illustrates a hearing assistance device (HA) comprising a user interface, here in the form of a separate (auxiliary) remote control device, here integrated with a portable telephone apparatus (TEL), e.g. a Smartphone. The hearing assistance device of FIG. 7 can be any one of the embodiments described in the present application. The hearing assistance device and the Smartphone are configured to allow a user to control functionality of the hearing assistance device, including to enable (cf. entry ‘Add sensor?’ in the display of the Smartphone TEL) or disable a particular external sensor to contribute to the control input signals to the control unit of the hearing assistance device via the user interface. In the embodiment of FIG. 7, the hearing assistance device and the Smartphone are configured to allow a user to configure a particular sensor contributing to the control input signals to the control unit via the user interface, e.g. by setting threshold values for entering a low-power mode (cf. entry ‘Change Criterion?’ in the display of the Smartphone TEL). In an embodiment, the sensors that are allowed to be added (and/or configured) to or removed from contributing inputs to the decision of entering (or leaving) a low-power mode of operation by a user are selected from a predefined list of sensors appearing on the user interface.

(33) FIG. 8 shows an embodiment of a hearing assistance device according to the present disclosure wherein the power distribution is schematically illustrated. The hearing assistance device of FIG. 8 can be any one of the embodiments described in the present application, and resembles the embodiment of FIG. 1. A difference is that the embodiment of a hearing assistance device of FIG. 8 only shows detectors DET1 and DET2, whereas DET3 and DET4 (feedback estimation unit FBE) are not included (not shown). Microphone (MIC) and loudspeaker (SPK) of FIG. 1 b are illustrated as input transducer (IT) and output transducer (OT), respectively, in FIG. 8. The external feedback path and the feedback cancellation system of FIG. 1a are not illustrated in FIG. 8. Instead, the separate power distribution to the functional blocks IT, OT, SPU, DET1, DET2, DET-CTR of the hearing assistance device is indicated. Separate conductors (pwr-IT, pwr-OT, pwr-SPU, pwr-DET1, pwr-DET2, pwr-CTR) supplying voltage and current (power) to respective functional blocks are connected to the energy source controlled by switch unit SW, which receives the supply voltage from the energy source (BAT, e.g. a battery) via conductor PWR. The switch unit (SW) comprises one or more switches (e.g. transistors) controlled by control signal BATC from the control unit (DET-CTR), as e.g. discussed in connection with FIG. 1. The power supply conductors may be individually controlled or controlled in groups according to a predefined scheme (e.g. in dependence of the current combination of control input signals (ID1, ID2, . . . ) to the control unit (DET-CTR). In an embodiment, the control (DET-CTR) and switch (SW) units are configured to selectively switch off the power supply to the signal processing unit (SPU, or a (significant) part thereof), when a low-power mode is decided by the control-unit to be entered. In an embodiment, power to the switch unit (SW) is ON when the hearing assistance device is in a low-power mode. In an embodiment, power to the switch unit (SW) and the control unit (DET-CTR) is ON when the hearing assistance device is in a low-power mode. In an embodiment, power to one or more of the detectors (DET1, DET2, . . . ) is also ON when the hearing assistance device is in a low-power mode. In an embodiment, power to a smaller number of the detectors (DET1, DET2, . . . ) are ON when the hearing assistance device is in a low-power mode compared to when the hearing assistance device is in a normal mode of operation. In an embodiment, only one of the detectors (DET1, DET2, . . . ), e.g. a movement detector, receives power, when the hearing assistance device is in a low-power mode.

EXAMPLES

(34) The general idea of letting a hearing assistance device, e.g. a hearing aid, automatically detect whether it needs to be ON or OFF (or in a low-power mode) solves the problem of avoiding having to manually switch it ON and OFF and to thereby minimize the manual handling of the hearing aid. In an ‘OFF-state’, the hearing aid is preferably not completely powered off. Instead, it is in a low-power mode where it is preferably running on ultra-low power and periodically (e.g. every second or every 10 seconds or once every 100 seconds) “snooping” or “polling” the relevant sensors. In an embodiment, relevant parts of the hearing assistance device are periodically powered ON (when in a low-power or OFF-mode), a relevant mode of operation is decided on and the relevant mode is activated. Alternatively the low-power mode could be a ‘completely OFF’ mode, which would require a manual power ON.

(35) In the following some ideas of how to automate an ON/OFF activation by one detector signal (e.g. to leave a low-power mode) or by a combination of at least two detector signals (to enter a low-power mode) are mentioned, exemplified by a hearing aid device.

(36) Temperature Sensor:

(37) A temperature sensor in a part of a hearing aid in contact with the skin of a user (e.g. a receiver assembly (an ITE-part) or a BTE-part) would make it possible to detect whether or not the hearing aid is placed in or at the ear. If the temperature of the sensor reaches the temperature of the human body (typically around 37.5° C.), then the hearing aid is turned ON (if in a low-power mode). If, on the other hand, the temperature reaches a level well below the human body temperature (e.g. ≧5° C. below), indicating that the hearing aid is presently not worn, the hearing aid may enter a low-power mode (be powered down, preferably provided that another sensor confirms or indicates the same). If the hearing aid needs to be able to automatically power on when placed in the ear, the hearing aid cannot be completely powered down. It would need to ‘snoop’ the temperature level at predefined intervals in time, e.g. every 1 second or so (or at a frequency≧0.1 Hz).

(38) Feedback Path Estimation Sensor:

(39) Another way of detecting whether the hearing aid is placed in or at the ear of a user is to estimate the acoustic feedback path, i.e. the transfer function of the loudspeaker, the sound out through the vent and the microphone. This transfer function may be considerably different a) when the hearing aid is operationally placed in or at an ear of the user and b) when it is out of the ear, e.g. located at a table or in a storage container (cf. also FIG. 6b, 6c and the description thereof). In an example based on the observation of the current feedback path estimate, the control unit of the hearing aid can conclude or indicate “hearing aid not worn”, if the feedback estimation sensor estimates a gain in the feedback path that is higher than a reference value that has been determined for the specific user. In general, a comparison of the current feedback path estimate with stored reference feedback paths provides a valuable indication of whether or not the hearing aid is located in an operational position.

(40) Internal Range Sensor:

(41) Usually when the hearing aids are taken off, they are kept close together (e.g. at a distance in the range of 1-5 cm), e.g. in a carry case, a storage box, a pouch, a charger station, in the pocket etc., and when they are placed in/on the ears they are separated by the head (e.g. at a distance larger than 10 cm, e.g. in the range of 14-24 cm). The detection of the current distance between the hearing aids can be achieved by using existing wireless technologies, e.g. by analyzing the signal strength of the internal wireless communication between the hearing aids. An indication of the current distance between the hearing aids of a binaural hearing aid system provides a valuable indication of whether or not the hearing aid is located in an operational position.

(42) Skin Capacitance Sensor:

(43) In an embodiment, the hearing aid comprises a skin capacitance sensor. Preferably, the hearing aid is configured to turn ON (leave a low-power mode), when the skin capacitance sensor indicates that it is in contact with skin. A capacitive sensor can be located either on the housing of a hearing aid BTE-part adapted for being located behind the ear of a user (sensing the skin behind the ear) or on the housing of an ITE-part adapted for being located in the ear canal (sensing the skin in the ear canal).

(44) Skin Resistance Sensor:

(45) In an embodiment, the hearing assistance device comprises a resistance sensor in the form of electronic circuitry capable of measuring electric resistance. A housing (or shell) of the hearing assistance device comprises two galvanic contacts where it contacts the skin of the wearer (e.g. behind the ear or in the ear canal) when properly mounted. The resistance sensor measures in regular intervals (e.g. every 10 s or every 100 s) the electric resistance across the two contacts. Depending on the measured resistance value, a resulting control input signal is generated indicating whether or not the hearing assistance device is presently being worn, and if not, a low-power mode can be preferably activated (controlled by the control unit). Two options occur: a) If we want no current consumption in low-power (OFF) mode, then the complete system needs to be powered down. This requires a manual reactivation to a normal mode of operation (ON). b) If a (low) ‘standby power consumption’ is permitted in the low-power mode, then the electronic circuit can continue monitoring the electric resistance across the galvanic contacts to detect re-mounting of the hearing assistance device (e.g. re-insertion or into the ear canal). In this case the control unit may automatically leave the low-power mode and switch to a normal mode of operation. Preferably, the hearing assistance device is adapted to use the two galvanic contacts for other purposes, e.g. as charging contacts for charging a rechargeable battery of the hearing assistance device. An exemplary embodiment of a hearing assistance device (HA) comprising a skin resistance sensor and allowing a control unit to receive power in a low-power mode is shown in FIG. 9. The hearing assistance device (HA) comprises a forward path from a microphone unit (MIC) to speaker unit (SPK). A signal IN from the microphone unit is processed in signal processing unit (SPU) of the forward path, and an enhanced signal OUT is forwarded to the speaker unit. The hearing assistance device (HA) comprises a housing (HA-SHELL) adapted for being located fully or partially in an ear canal of a user. The housing (HA-SHELL) comprises two electric contact terminals (T1, T2) adapted for contacting the skin (SKIN) of the user when the housing is operationally mounted. One terminal (T1) is connected to a reference potential (here ground GND). The other terminal (T2) is connected to an A/D converter and control unit (A/D CTR). The hearing assistance device (HA) further comprises a reference resistor (R-REF) connected with one terminal in series with the skin resistance (R-SKIN) and another terminal connected to a reference voltage (e.g. as here a voltage of the battery (BAT)). This measurement circuit allows a determination of the skin resistance, e.g. by a voltage division measurement, and thereby it can be estimated by the control unit (A/D CTR) whether or not the hearing assistance device is operationally mounted on the user. The switching of the hearing assistance device into a low-power mode (preferably based on at least one other sensor control input signal) can be performed by switch (SW1) controlled by signal SWCTR from the control unit. In a closed state of switch (SW1) (normal mode), the signal processing unit (SPU) receives power from the battery (BAT), whereas this is not the case when the switch is open (low-power mode). In this state (the low-power mode) the battery voltage is still supplied to the control unit (A/D CTR) allowing a continuous or regular monitoring of the skin resistance to verify whether the hearing assistance device is again operationally mounted on the user, in which case the low-power mode can be deactivated by closing switch SW1.

(46) Skin Sensor Based on Light Emission/Detection

(47) As an alternative to a capacitive or resistance based sensor to detect the proximity of human skin, a combination of a Light emitting diode (e.g. at infrared (IR) frequencies), and a photo diode/transistor or a Pyroelectrical InfraRed (PIR) sensor (a passive infrared sensor), can be used. Such sensors can be incorporated into the shell of the hearing assistance device. This has the following advantages: When the sensor detects that the hearing assistance device is removed from the ear, the control unit controls a switch that enables the low-power mode, in which only the most necessary blocks are still running (receive power). These preferably include at least the sensors that are used in order to detect when the hearing assistance device is reinserted/repositioned in/on the ear. In an embodiment, where the entire audio path is powered down in the low-power mode, a tone caused by feedback between the microphone and the receiver is avoided. When the hearing assistance device is reinserted/repositioned in/on the ear, the sensors will detect the change, and the hearing assistance device will power up again (leave the low-power mode and switch to a normal mode). Alternatively, a manually operable activation element (e.g. a push button) may provide the event responsible for powering up the hearing assistance device again.

(48) Combinations of Sensors:

(49) To reduce the risk of false detections, embodiments of the present disclosure comprise the following combinations of detectors or indicators:

(50) In an embodiment, a “hearing aid not worn” conclusion is only made, if a temperature sensor indicates that the temperature has been dropping by predefined amount (e.g. more than 1° K) over a predefined time (e.g. during the last hour) AND if a force sensor on the left hand side of the hearing aid estimates a force that is less than half or more than double the force estimated by an equivalent force sensor on the right hand side of the hearing aid.

(51) In an embodiment, the hearing aid comprises a GMR sensor and a voice activity detector. Simultaneous GMR detection and NO VOICE detection (both indicating a location of the hearing aids in a storage box comprising a permanent magnet) results in an activation of a low-power mode.

(52) In an embodiment, each hearing aid of a binaural hearing aid system comprises a GMR sensor and comprises a wireless interface allowing the hearing aids to exchange signals (including sensor signals) between them. Simultaneous GMR detection on both hearing aids (indicating the location of both hearing aids in a storage box comprising a permanent magnet) results in an activation of a low-power mode in both devices.

(53) In an embodiment, each hearing aid of a binaural hearing aid system comprises a feedback detection sensor. Substantially different feedback path detection (possibly combined with simultaneous GMR detection) results in an activation of a low-power mode.

(54) In an embodiment, each hearing aid of a binaural hearing aid system comprises a field strength detector. Detection of a high signal strength between wirelessly connected hearing aids indicate that they are located close together (not in an operational position). This information can e.g. be combined with a simultaneous detection of a permanent magnet by a GMR sensor to result in an activation of a low-power mode.

(55) Entering a Low-Power Mode:

(56) Once the control unit has made a “hearing aid not worn” conclusion, it automatically operates a switch in the hearing aid (cf. switch unit SW in FIGS. 1a and 8) that powers down the hearing aid (or mutes it, or switches it to a low-power mode, etc.).

(57) In an embodiment, a hearing aid comprises a multitude of sensors and/or the hearing aid can be configured to be in communication with external sensors and to receive relevant sensor signals (by wire or wirelessly). The multitude of sensors can for example contain at least one of the following ‘sensors’: Sensors using circuit access points in the hearing aid circuitry to monitor the signal processing of the hearing aid (e.g. of the forward path of the hearing aid), e.g. signal level, feedback, etc. Positive or Negative Temperature Coefficient (PTC or NTC) resistors for temperature surveillance. Photo diodes or photo transistors for light detection. GMR sensors for magnetic field detection. Electrodes for conductivity measurements on skin or other surfaces. Microphones for acoustic environment detection. Acceleration sensors for linear movement detection. Gyrators for radial movement detection. Force meter to measure the exchange of forces between the hearing aid and the skin of its user while the hearing aid is being worn, and the exchange of the hearing aid and its repository while it is not being worn.

(58) Implementing a Low-Power Mode:

(59) In the following, an integrated switch which can be used to implement a low-power mode in a hearing assistance device, such as a hearing aid, e.g. to turn off power to all parts of the device, is presented. In particular an integrated switch specifically adapted for using rechargeable batteries as a local source of energy is described.

(60) A hearing assistance device using rechargeable batteries cannot be allowed to draw current from the battery indefinitely, because a too deep discharge can destroy some types of rechargeable battery, for example NiMH. The hearing assistance device must thus monitor the state of the rechargeable battery and decide when to stop drawing current from the battery, or at least reduce the current to insignificant levels.

(61) In an embodiment, the power switch is implemented a MOS transistor switch, e.g. residing on one of the chips of the hearing assistance device. All power from the battery is routed through this switch, so no current can be drawn when the switch is off. In an embodiment, the switch is turned on by a user input (e.g. pushing a button or otherwise activating the power switch) or electronically (by asserting a control signal, e.g. via a remote control). Subsequently, the hearing aid steps through a wake-up procedure, as is state of the art if a normal (non-rechargeable, e.g. Zinc-Air) battery had been inserted into a traditional hearing assistance device.

(62) After a period of normal use, the battery will slowly discharge to a given end-of-life level. In the case of NiMH batteries, this level is around 900 mV. At that point, no more current may be drawn from the battery without damaging it permanently.

(63) This threshold crossing is preferably detected by a circuit on one of the chips of the hearing assistance device, and a predefined shut down procedure is initiated (e.g. controlled by the control unit, possibly taking into account other control input signals). Shut down is e.g. initiated by opening the switch (cutting off the current), stopping the draw on the battery. Thereby a storage of hearing assistance devices with rechargeable batteries for extended periods of time, without discharging, is enabled. This is a requirement for selling hearing assistance devices with rechargeable (e.g. NiMH or LiIon) batteries pre-installed in the hearing assistance device.

(64) FIG. 10 shows a PCB for a portable hearing assistance device comprising a rechargeable battery B, e.g. a Li-Ion or a NiMH battery. The battery has a positive terminal V+ and a negative terminal V− connected to ground GND. The positive terminal is connected to a switch S whose state is controlled by a battery voltage monitoring circuit BM (and/or a control unit integrated there with to evaluate different sensor signals). The battery voltage monitoring circuit BM gets its input from the positive terminal of the battery voltage, either taken before the switch S (V+1) or after the switch (V+2), and from the negative terminal of the battery (V−). In the case, where the positive voltage input is taken after the switch (dashed connection to terminal V+2 on the BM circuit) the power supply to the a battery voltage monitoring circuit is off when the switch is open (requiring a manual power-up (manually closing the switch S by a user-operable activation element on the portable hearing assistance device)). In this configuration, the battery voltage monitoring circuit BM (and control unit) may be used to implement an automatic activation of a low-power mode (e.g. a power down) when the measured voltage is below a threshold voltage Vpd (or when the control unit decides so based on the at least two control input signals). When the positive voltage input is taken before the switch (input V+1 on the BM circuit), the battery voltage monitoring circuit BM (and a control unit and possible sensors integrated there with) is always connected to the battery and may additionally be used to implement an automatic deactivation of the low-power mode, e.g. a power up) when the measured voltage is above a predefined threshold voltage Vpu (and/or when the control unit decides to do so). A capacitor C is connected in parallel over the battery to stabilize the voltage. The positive and negative (GND) voltages are distributed to corresponding terminals V+ and V−, respectively, on various components on the PCB, here an analogue IC (A-IC), a digital IC (D-IC) and two electronic modules (M-1 and M-2), e.g. sensors, transducers, tele-coil circuitry, etc., are shown.

(65) The invention is defined by the features of the independent claim(s). Preferred embodiments are defined in the dependent claims. Any reference numerals in the claims are intended to be non-limiting for their scope.

(66) Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims and equivalents thereof.