Hearing device with acoustic shock control and method for acoustic shock control in a hearing device

Abstract

A hearing device for being worn at or at least partly within an ear of a user and including an acoustic shock detector for detecting an acoustic shock event present in an input audio signal from an input transducer and providing shock detection information related to the acoustic shock event. The hearing device further includes an acoustic shock controller for determining a first gain factor (G.sub.b) and a second gain factor (G.sub.p) in dependence of the shock detection information, a first attenuator for attenuating a processed input audio signal by the first gain factor (G.sub.b) and providing an attenuated audio signal to an output limiter providing a limited audio signal, and a second attenuator for attenuating the limited audio signal by the second gain factor (G.sub.p) and providing a further attenuated audio signal to an output transducer. A corresponding method for acoustic shock control in a hearing device.

Claims

1. A hearing device structured to be worn at or at least partly within an ear of a user of the hearing device comprising: an input transducer (1) structured and configured to receive an audio signal and to convert the received audio signal into an input audio signal; an audio signal processor (15′) structured and configured to process the input audio signal and to provide a processed audio signal; an output limiter (2) structured and configured to limit a signal level of a signal applied to an input of the output limiter to a maximum signal level and to provide a limited audio signal; an output transducer (3) structured and configured to convert a signal applied to an input of the output transducer (3) into an output audio signal to be provided to the user; and an acoustic shock detector (4) structured and configured to detect an acoustic shock event present in the input audio signal and to provide shock detection information related to the acoustic shock event, characterised in that the hearing device further comprises: an acoustic shock controller (5) structured and configured to determine a first gain factor (G.sub.b) and a second gain factor (G.sub.p) in dependence of the shock detection information; a first attenuator (6) structured and configured to attenuate the processed audio signal by the first gain factor (G.sub.b) and to provide an attenuated audio signal to the input of the output limiter (2); and a second attenuator (7) structured and configured to attenuate the limited audio signal by the second gain factor (G.sub.p) and to provide a further attenuated audio signal to the input of the output transducer (3).

2. The hearing device of claim 1, wherein the acoustic shock controller (5) is adapted to determine a total gain factor (G.sub.a) as well as a first gain distribution coefficient (r.sub.b) and a second gain distribution coefficient (r.sub.p), all in dependence of the shock detection information, and wherein the total gain factor (G.sub.a) is the product of the first and second gain factors (G.sub.a, G.sub.p), and the sum of the first gain distribution coefficient (r.sub.b) and the second gain distribution coefficient (r.sub.p) is a constant, and wherein the first gain factor (G.sub.b) is determined as the total gain factor (G.sub.a) multiplied by the first gain distribution coefficient (r.sub.b) and the second gain factor (G.sub.p) is determined as the total gain factor (G.sub.a) multiplied by the second gain distribution coefficient (r.sub.p).

3. The hearing device of claim 1, wherein the acoustic shock controller (5) is adapted to adjust the first gain factor (G.sub.b) and the second gain factor (G.sub.p) in dependence of a degree of saturation (S) of the limited audio signal, and wherein the acoustic shock controller (5) is in particular adapted to increase the first gain factor (G.sub.b) and to decrease the second gain factor (G.sub.p) when the degree of saturation (S) decreases.

4. The hearing device of claim 1, wherein the acoustic shock controller (5) is adapted to adjust the first gain factor (G.sub.b) and the second gain factor (G.sub.p) in dependence of the maximum signal level of the output limiter (2).

5. The hearing device of claim 1, wherein the hearing device further comprises an audio analyser (10), in particular being or comprising a sound classifier, for determining a type of a momentary acoustic environment (AE) based on the input audio signal, and wherein the acoustic shock controller (5) is adapted to adjust the first gain factor (G.sub.b) and the second gain factor (G.sub.p) in dependence of the type of the momentary acoustic environment (AE), as well as in particular to adjust the total gain factor (G.sub.a) as well as the first gain distribution coefficient (r.sub.b) and the second gain distribution coefficient (G.sub.p) in dependence of the type of the momentary acoustic environment (AE).

6. The hearing device of claim 1, wherein the acoustic shock detector (5) is adapted to detect a type of the acoustic shock event and to provide the type of the acoustic shock event as part of the shock detection information, and wherein the acoustic shock controller (5) is adapted to adjust the first gain factor (G.sub.b) and the second gain factor (G.sub.p) in dependence of the type of the acoustic shock event, as well as in particular to adjust the total gain factor (G.sub.a) as well as the first gain distribution coefficient (r.sub.b) and the second gain distribution coefficient (r.sub.p) in dependence of the type of the acoustic shock event.

7. The hearing device of claim 1, wherein the hearing device further comprises: an analysis filter bank (8) structured and configured to decompose the input audio signal into a plurality of band-limited input audio signals each associated with a corresponding frequency band; and a synthesis filter bank (9) structured and configured to combine or compose a plurality of band-limited input signals of the synthesis filter bank (9) into a single signal provided to the input of the output transducer (3), wherein the audio signal processor (15′) processes each of the band-limited input audio signals to provide a plurality of processed band-limited audio signals, and wherein the acoustic shock controller (5) is adapted to determine a first frequency-dependent gain factor (G.sub.b,i) and a second frequency-dependent gain factor (G.sub.b,i) for each frequency band in dependence of the shock detection information, and wherein the first attenuator (6) is adapted to attenuate each of the processed band-limited audio signals by the corresponding first frequency-dependent gain factor (G.sub.b,i) and to provide a plurality of attenuated band-limited audio signals, and wherein the output limiter (2) is adapted to limit the signal level of each of the plurality of attenuated audio signals to a maximum signal level, wherein in particular the maximum signal level is individual for each frequency band, and to provide a plurality of band-limited limited audio signals, and wherein the second attenuator (7) is adapted to attenuate each of the band-limited limited audio signals by the corresponding second frequency-dependent gain factor (G.sub.p,i) and to provide a plurality of further attenuated audio signals as input signals to the synthesis filter bank (9).

8. The hearing device of claim 7, wherein the acoustic shock controller (5) is adapted to determine a total frequency-dependent gain factor (G.sub.a,i) as well as a first frequency-dependent gain distribution coefficient (r.sub.b,i) and a second frequency-dependent gain distribution coefficient (r.sub.p,i) for each frequency band, all in dependence of the shock detection information, and wherein the total frequency-dependent gain factor (G.sub.a,i) is the product of the first and second frequency-dependent gain factors (G.sub.b,i, G.sub.p,i) for each frequency band, and the sum of the first frequency-dependent gain distribution coefficient (r.sub.b,i) and the second frequency-dependent gain distribution coefficient (r.sub.p,i) is a constant for each frequency band, and wherein the first frequency-dependent gain factor (G.sub.b,i) is determined as the total frequency-dependent gain factor (G.sub.a,i) multiplied by the first frequency-dependent gain distribution coefficient (r.sub.b,i) and the second frequency-dependent gain factor (G.sub.p,i) is determined as the total frequency-dependent gain factor (G.sub.a,i) multiplied by the second frequency-dependent gain distribution coefficient (r.sub.p,i) for each frequency band.

9. The hearing device of claim 7, wherein the acoustic shock controller (5) is adapted to adjust the first frequency-dependent gain factor (G.sub.b,i) and the second frequency-dependent gain factor (G.sub.p,i) in dependence of a frequency-dependent degree of saturation (S.sub.i) of the band-limited limited audio signal for each frequency band, and wherein the acoustic shock controller (5) is in particular adapted to increase the first frequency-dependent gain factor (G.sub.b,i) and to decrease the second frequency-dependent gain factor (G.sub.p,i) when the frequency-dependent degree of saturation (S.sub.i) decreases.

10. The hearing device of claim 5, wherein the acoustic shock controller (5) is adapted to adjust the first frequency-dependent gain factor (G.sub.b,i) and the second frequency-dependent gain factor (G.sub.p,i) for each frequency band in dependence of the type of the momentary acoustic environment (AE).

11. The hearing device of claim 6, wherein the acoustic shock controller (5) is adapted to adjust the first frequency-dependent gain factor (G.sub.b,i) and the second frequency-dependent gain factor (G.sub.p,i) for each frequency band in dependence of the type of the acoustic shock event.

12. The hearing device of claim 1, wherein the acoustic shock controller (5) is adapted to adjust the first gain factor (G.sub.b) and the second gain factor (G.sub.p), or alternatively the first frequency-dependent gain factor (G.sub.b,i) and the second frequency-dependent gain factor (G.sub.p,i) for each frequency band, or the total gain (G.sub.a), or alternatively the total frequency-dependent gain (G.sub.a,i) for each frequency band, in dependence of personal preferences (PP) of the user.

13. The hearing device of claim 12, wherein the hearing device further comprises a control element structured and configured to receive user inputs, and wherein the acoustic shock controller is adapted to adjust the personal preferences (PP) in dependence of the user inputs, and wherein in particular the hearing device is adapted to receive initial personal preferences (PP) from a fitting device.

14. The hearing device of claim 1, wherein the hearing device further comprises a transceiver adapted to transmit information to and to receive information from a second hearing device and intended to be worn at or at least partly within another ear of the user, wherein said information comprises at least one of the following: the shock detection information; the first gain factor (G.sub.b) and/or the second gain factor (G.sub.p); the first frequency-dependent gain factor (G.sub.b,i) and/or the second frequency-dependent gain factor (G.sub.p,i) for one or more of the frequency bands; the total gain factor (G.sub.a) and/or the first gain distribution coefficient (r.sub.b) and/or the second gain distribution coefficient (r.sub.p); the total frequency-dependent gain factor (G.sub.a,i) and/or the first frequency-dependent gain distribution coefficient (r.sub.b,i) and/or the second frequency-dependent gain distribution coefficient (r.sub.p,i) for one or more of the frequency bands; the type of the momentary acoustic environment (AE); the type of the acoustic shock event, wherein the acoustic shock controller (5) is adapted to apply the information received from the other hearing device to determine at least one of the following in the hearing device: the shock detection information; the first gain factor (G.sub.b) and/or the second gain factor (G.sub.p); the first frequency-dependent gain factor (G.sub.b,i) and/or the second frequency-dependent gain factor (G.sub.p,i) for one or more of the frequency bands; the total gain factor (G.sub.a) and/or the first gain distribution coefficient (r.sub.b) and/or the second gain distribution coefficient (r.sub.p); the total frequency-dependent gain factor (G.sub.a,i) and/or the first frequency-dependent gain distribution coefficient (r.sub.b,i) and/or the second frequency-dependent gain distribution coefficient (r.sub.p,i) for one or more of the frequency bands; the type of the momentary acoustic environment (AE); the type of the acoustic shock event.

15. A method for acoustic shock control in a hearing device intended to be worn at or at least partly within an ear of a user of the hearing device, comprising the steps of: a) receiving an audio signal and based thereupon providing an input audio signal; b) detecting an acoustic shock event present in the input audio signal and providing shock detection information related to the acoustic shock event; c) processing the input audio signal and providing a processed audio signal; d) determining a first gain factor (G.sub.b) and a second gain factor (G.sub.e) in dependence of the shock detection information; e) attenuating the processed audio signal by the first gain factor (G.sub.b) and providing an attenuated audio signal; f) limiting a signal level of the attenuated audio signal to a maximum signal level and providing a limited audio signal; g) attenuating the limited audio signal by the second gain factor (G.sub.e) and providing a further attenuated audio signal as an output audio signal; and h) outputting the output audio signal to the user.

16. The method of claim 15, further comprising the steps of: decomposing the input audio signal into a plurality of band-limited input audio signals each associated with a corresponding frequency band; and combining or composing a plurality of band-limited output audio signals into a single output audio signal, wherein steps c) to g) are performed individually for each frequency band.

17. The method of claim 15, further comprising the steps of: transmitting information to a second hearing device intended to be worn at or at least partly within another ear of the user; receiving information from the second hearing device, wherein said information comprises at least one of the following: the shock detection information; the first gain factor (G.sub.b) and/or the second gain factor (G.sub.p); the first frequency-dependent gain factor (G.sub.b,i) and/or the second frequency-dependent gain factor (G.sub.p,i) for one or more of the frequency bands; the total gain factor (G.sub.a) and/or the first gain distribution coefficient (r.sub.b) and/or the second gain distribution coefficient (r.sub.p); the total frequency-dependent gain factor (G.sub.a,i) and/or the first frequency-dependent gain distribution coefficient (r.sub.b,i) and/or the second frequency-dependent gain distribution coefficient (r.sub.p,i) for one or more of the frequency bands; the type of the momentary acoustic environment (AE); the type of the acoustic shock event, and wherein the information received from the other hearing device is employed for determining at least one of the following in the hearing device: the shock detection information; the first gain factor (G.sub.b) and/or the second gain factor (G.sub.p); the first frequency-dependent gain factor (G.sub.b,i) and/or the second frequency-dependent gain factor (G.sub.p,i) for one or more of the frequency bands; the total gain factor (G.sub.a) and/or the first gain distribution coefficient (r.sub.b) and/or the second gain distribution coefficient (r.sub.p); the total frequency-dependent gain factor (G.sub.a,i) and/or the first frequency-dependent gain distribution coefficient (r.sub.b,i) and/or the second frequency-dependent gain distribution coefficient (r.sub.p,i) for one or more of the frequency bands; the type of the momentary acoustic environment (AE); the type of the acoustic shock event.

18. The hearing device of claim 1, wherein the acoustic shock controller (5) is connected between the acoustic shock detector (4) and the output limiter (2).

19. The hearing device of claim 1, wherein the audio signal is attenuated by the first gain factor (G.sub.b) before the output limiter (2) and by the second gain factor (GO after the output limiter (2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further explained below by means of non-limiting specific embodiments/examples and with reference to the accompanying drawings, which show:

(2) FIG. 1 a high-level block diagram of a prior art scheme where fast shock detection is performed in the time-domain and anti-shock control is applied in the frequency-domain;

(3) FIG. 2 a block diagram of a hearing device with acoustic shock control exemplifying a variety of possible embodiments according to the present invention;

(4) FIG. 3 a further block diagram of a hearing device with acoustic shock control exemplifying a variety of possible further embodiments according to the present invention;

(5) FIG. 4 a graph illustrating an exemplary frequency shaping according to the present invention resulting from applying a frequency-dependent gain G(f) (plotted as an attenuation function 1/G(f)); and

(6) FIG. 5 a schematic high-level block diagram of a binaural hearing system comprising a left and a right hearing device with coordinated acoustic shock control according to the present invention.

(7) In the figures, like reference signs refer to like parts.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 illustrates in a high-level block diagram a prior art anti-shock system as provided in U.S. Pat. No. 7,983,425 B2 (cf. FIG. 6 therein). The sound is picked up by a microphone providing an input signal s(t) and then transformed from the time-domain to the frequency-domain, e.g. by an analysis filter bank 14 or a fast Fourier transform (FFT). A fast shock detector 12 operating in the time-domain can detect the presence of an acoustic shock event in the input signal s(t), and determine how strong the shock is, what kind of shock it is and can adapt to the changes in the acoustic environment by detecting the relative shock and the absolute shock. The anti-shock control 13 will immediately react to the detected shock without delay and apply an appropriate gain/attenuation as part of the frequency-domain processing 15. Subsequently, the frequency-domain signal is transformed back to the time-domain, e.g. by a synthesis filter bank 16 (e.g. a summer/combiner) or an inverse FFT (IFFT), and the resulting signal y(t) is output for instance by means of a receiver.

(9) FIG. 2 depicts a block diagram of a hearing device with acoustic shock control exemplifying a variety of possible embodiments according to the present invention. An audio signal (sound) is picked up by the input transducer 1, e.g. a microphone, and provided as an input signal to a processor 11, such as a digital signal processor (DSP), to be processed according to the needs and preferences of a user of the hearing device. The processed signal is subsequently output by an output transducer 3, such as a miniature loudspeaker (also commonly referred to as receiver), a cochlear implant or a direct acoustic cochlear stimulator (DACS). In an embodiment the input signal is transformed from the time-domain to the frequency-domain, e.g. by an analysis filter bank 8 or an FFT. Subsequently, the transformed signal is processed in the frequency-domain in block 15′, such as applying a frequency-dependent gain in order to compensate the user's hearing loss/impairment. Typically (i.e. in the prior art), the processed signal is then applied to an output limiter 2 to limit the signal to a maximum signal level before being transformed back to the time-domain, e.g. by a synthesis filter bank 9 or an IFFT. However, according to the present invention the processed signal is additionally attenuated by a first attenuator 6 by a first gain/attenuation factor G.sub.b prior to the output limiter 2 and further attenuated by a second attenuator 7 by a second gain/attenuation factor G.sub.p after the output limiter 2. In this way it is possible to ensure that shock events remain perceivable even in situations where the input signal would traditionally be severely clipped and the output signal provided to the output transducer 3 is entirely saturated. The first and second gain/attenuation factors G.sub.b, G.sub.p are determined by an acoustic shock controller 5 dependent on shock detection information provided by an acoustic shock detector 4. Such shock detection information may for instance be information regarding a signal floor, a peak signal level, a shock contrast level (e.g. a difference between the peak signal level and the signal floor), an attack time, a shock index (e.g. based on the shock contrast level and the attack time), the duration of the shock or the type of shock. In an embodiment according to FIG. 2 the acoustic shock detector 4 is implemented in the time-domain in order to achieve very fast detection and the processing is performed in the frequency-domain. Because transforming the input signal from the time-domain into the frequency-domain incurs a delay the first and second gain/attenuation factors G.sub.b, G.sub.p can be determined by the acoustic shock controller 5 in time to be applied to the delayed processed signal containing the shock in the frequency-domain. However, it is also conceivable that the processing of the input signal as well as the shock detection are both performed in the time-domain or that the processing of the input signal as well as the shock detection are both performed in the frequency-domain.

(10) Alternatively to directly determining the two gain/attenuation factors G.sub.b, G.sub.p, the acoustic shock controller 5 may calculate a total gain/attenuation factor G.sub.a along with a first gain distribution coefficient r.sub.b and a second gain distribution coefficient r.sub.p, whereby the sum of the two equals one (r.sub.b+r.sub.p=1), and the first gain/attenuation factor is equal to the product of the total gain/attenuation factor G.sub.a and the first gain distribution coefficient r.sub.b (G.sub.b=G.sub.a×r.sub.b) and the second gain/attenuation factor is equal to the product of the total gain/attenuation factor G.sub.a and the second gain distribution coefficient r.sub.p (G.sub.p=G.sub.a×r.sub.p), as indicated by the multipliers in FIG. 2.

(11) The acoustic shock controller 5 may for instance adjust the first gain/attenuation factor G.sub.b and the second gain/attenuation factor G.sub.p in dependence of a degree of saturation S of the limited audio signal. In particular, the acoustic shock controller 5 may increase the first gain factor G.sub.b and decrease the second gain factor G.sub.p when the degree of saturation S decreases, and vice-versa. The acoustic shock controller 5 may correspondingly adjust the first and second gain distribution coefficients r.sub.b, r.sub.p in dependence of the degree of saturation S. The degree of saturation S is for instance given by the relative amount of time where the signal level of the signal applied to the input of the output limiter 2 exceeds the maximum signal level of the output limiter 2, i.e. where the input signal is clipped. Alternatively, the degree of saturation S is for instance given by the ratio of the maximum value of the signal applied to the input of the output limiter 2 and the mean value of the signal applied to the input of the output limiter 2.

(12) Furthermore, the acoustic shock controller 5 may for instance adjust the first gain/attenuation factor G.sub.b and the second gain/attenuation factor G.sub.p (and correspondingly the first and second gain distribution coefficients r.sub.b, r.sub.p) in dependence of the maximum signal level of the output limiter 2, which can be pre-set for instance by a fitter of the hearing device.

(13) Moreover, the acoustic shock controller 5 may adjust the first gain/attenuation factor G.sub.b and the second gain/attenuation factor G.sub.p (or the total gain factor G.sub.a and correspondingly the first and second gain distribution coefficients r.sub.b, r.sub.p) in dependence of the type of the momentary acoustic environment AE, which is determined by an audio analyser 10 (being or comprising a sound classifier).

(14) Additionally, the acoustic shock controller 5 may adjust the first gain/attenuation factor G.sub.b and the second gain/attenuation factor G.sub.p (or the total gain factor G.sub.a and correspondingly the first and second gain distribution coefficients r.sub.b, r.sub.p) in dependence of personal preferences PP of the user, which are determined during fitting of the hearing device to the individual user.

(15) FIG. 3 depicts a further block diagram of a hearing device with acoustic shock control exemplifying a variety of possible further embodiments according to the present invention. The difference between the embodiments shown in FIGS. 2 & 3 is that in FIG. 3 the applied gains/attenuations G.sub.b,i, G.sub.p,i are individual/specific for different frequency bands Fi (likewise for G.sub.a,i, r.sub.b,i & r.sub.p,i). Furthermore, the acoustic shock controller 5 may adjust these gains/attenuations G.sub.b,i, G.sub.p,i in dependence of a frequency-dependent degree of saturation S.sub.i, which in turn may be dependent the personal preferences PP of the user based on his individual hearing loss/impairment such as given by the user's audiogram.

(16) An exemplary frequency shaping of the gain/attenuation provided by the embodiments shown in FIG. 3 are illustrated in FIG. 4, which depicts a graph of the frequency-dependent attenuation functions 1/G.sub.a, 1/G.sub.b & 1/G.sub.p, where a high attenuation is applied to high audio frequencies and a low attenuation is applied to low audio frequencies. In this graph the attenuation is greater than one (1/G(f)>1), i.e. the gain is less than one (G(f)<1). On a logarithmic (decibel) scale attenuations are negative and gains are positive.

(17) FIG. 5 schematically depicts a high-level block diagram of a binaural hearing system comprising a left and a right hearing device. Each hearing device comprises it own acoustic shock controller ASC, however these two acoustic shock controllers are linked to one another, e.g. wirelessly, to allow coordination between them. This is advantageous in order to ensure that shock events can be localised correctly by a user of the binaural hearing system. To achieve this for instance shock detection information, the gain factors G.sub.b and G.sub.p, etc. may be exchanged between the two hearing devices, so that the left hearing device is aware of how an acoustic shock event is detected/registered by the right hearing device (and vice-versa) and how the hearing devices would independently react to the shock event, allowing the reaction to be modified, in particular aligned, to ensure correct localisation of the shock source.

(18) The proposed shock control scheme according to the present invention based on distributing an overall/total shock control gain G.sub.a before (G.sub.b) and after (G.sub.p) the output limiter 2 provides an adaptive and intelligent anti-shock mechanism keeping the acoustic shock event perceivable in a natural and comfortable manner for all users and in all hearing situations, without unduly impacting desired target signals such as speech or music. Moreover, the proposed binaurally coordinated anti-shock scheme according to the present invention preserves localisation information such that the acoustic shock events are also perceived in a natural and comfortable way. Hence, the acoustic shock control according to the present invention achieves the following objectives: reduces (or minimises) the shock impact; keeps the sound natural to allow awareness by the user of the type of shock event; retains the relative loudness of a shock so that the user can perceive the shock level; and maintains the shock within the comfort range of the user.

(19) As can be seen in the extreme case where the anti-shock gain control is completely applied after the output limiter (i.e. G.sub.b=1, G.sub.p=G.sub.a), the user is still able to perceive the shock even when the signal at the output of the limiter is fully saturated. Therefore, shock awareness is maintained in all situations.

(20) The acoustic shock control proposed by the present invention therefore provides the following benefits: Even for hearing devices applying a very high amplification due to a severe hearing loss of the user, thus driving the hearing device to be nearly or fully saturated, the proposed anti-shock gain control scheme ensures that acoustic shock events remain perceivable to all users and in all hearing situations. By restricting attenuation of the output signal to those frequency bands in which the shock signal is present the desired target signal, e.g. speech or music, is not detrimentally effected. The proposed adaptive anti-shock scheme is adapted to prevailing acoustic environment and thus delivers the best performance for different hearing situations. The proposed anti-shock scheme is personalised dependent on the individual user's needs or preferences and therefore provides the best benefit for different individuals. In binaural hearing systems the proposed coordinated anti-shock scheme takes into account that shock signals may have different intensity levels and temporal characteristics at the two hearing devices depending on where the source of the shock event is located. Therefore, information is exchanged between the acoustic shock controllers of the two hearing devices, in order to avoid the situation where a shock is only detected by one of the hearing devices, which then attenuates the shock signal, whilst the other hearing device does not react to the shock, hence making it difficult for the user to localise where the shock signal is coming from.