BINAURAL HEARING SYSTEM AND METHOD FOR OPERATING A BINAURAL HEARING SYSTEM

Abstract

A method for operating a binaural hearing system having first and second hearing instruments includes using respective electroacoustic first and second input transducers of the first and second hearing instruments to generate first and second input signals from ambient sound. The first and second input signals are used to ascertain respective first and second instantaneous gain parameters. A first parameter of an automatic gain control for the first input signal and/or a second parameter of an automatic gain control for the second input signal is/are adjusted so that the adjustment results in a difference between the first and second instantaneous gain parameters being decreased. Signal processing for the first or second input signal using the thus adjusted first or second parameter of the automatic gain control is performed in the first or second hearing instrument. A binaural hearing system is also provided.

Claims

1. A method for operating a binaural hearing system, the method comprising: providing a first hearing instrument and a second hearing instrument; using an electroacoustic first input transducer of the first hearing instrument to generate a first input signal from ambient sound, and using an electroacoustic second input transducer of the second hearing instrument to generate a second input signal from ambient sound; using the first input signal to ascertain a first instantaneous gain parameter, and using the second input signal to ascertain a second instantaneous gain parameter; adjusting at least one of a first parameter of an automatic gain control for the first input signal or a second parameter of an automatic gain control for the second input signal, the adjustment resulting in a difference between the first and the second instantaneous gain parameters being decreased; and performing a signal processing for the first or second input signal using the adjusted first or second parameter of the automatic gain control in the first or second hearing instrument.

2. The method according to claim 1, which further comprises adjusting the first or second instantaneous gain parameter as the first or second parameter of the automatic gain control.

3. The method according to claim 1, which further comprises adjusting at least one of a compression ratio or a knee of a compression characteristic curve or an attack time or a release time of a compression, as the first or second parameter of the automatic gain control.

4. The method according to claim 1, which further comprises: using the first input signal and the second input signal to at least approximately determine a direction of a sound source relating to the ambient sound; and additionally basing the adjustment to the first or second parameter of the automatic gain control on the ascertained direction of the sound source.

5. The method according to claim 4, which further comprises making the adjustment to the first or second parameter of the automatic gain control to a greater degree the closer the ascertained direction of the sound source is to a frontal direction of the binaural hearing system.

6. The method according to claim 4, which further comprises: carrying out the approximate determination of the direction of the sound source by ascertaining a focus half-area containing the sound source and a background half-area being remote from the focus half-area, the focus half-area and the background half-area being defined relative to a plane of symmetry of the binaural hearing system; and carrying out the adjustment to the first or second parameter of the automatic gain control by also using the first or second instantaneous gain parameter relating to the focus half-area, or a signal level in the focus half-area.

7. The method according to claim 1, which further comprises: carrying out the adjustment to the first or second parameter of the automatic gain control by ascertaining at least one of a first correction parameter or a second correction parameter; and forming an adjusted first or second parameter based on a respective convex combination of the first parameter with the first correction parameter or the second parameter with the second correction parameter.

8. The method according to claim 1, which further comprises: transmitting the first input signal, or a first transmission signal derived from the first input signal, from the first hearing instrument to the second hearing instrument; ascertaining the first and the second instantaneous gain parameters locally in the second hearing instrument; and taking the first and the second instantaneous gain parameters as a basis for adjusting the second parameter of the automatic gain control for the signal processing of the second input signal in the second hearing instrument.

9. The method according to claim 8, which further comprises carrying out the local ascertainment of the first and the second instantaneous gain parameters in the second hearing instrument by using a respective specifically dedicated hardwired circuit.

10. The method according to claim 1, which further comprises carrying out the method frequency band by frequency band.

11. The method according to claim 8, which further comprises carrying out the method frequency band by frequency band, and transmitting only lower frequency bands of the first input signal to the second hearing instrument as the first transmission signal.

12. The method according to claim 9, which further comprises carrying out the method frequency band by frequency band, and transmitting only lower frequency bands of the first input signal to the second hearing instrument as the first transmission signal.

13. A binaural hearing system comprising: a first hearing instrument and a second hearing instrument; the binaural hearing system configured to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0038] FIG. 1a is a diagrammatic, plan view showing a conversation situation;

[0039] FIG. 1b is a plan view showing the effect of dynamic compression in the binaural hearing system on the spatial auditory perception of the conversation situation shown in FIG. 1a by the wearer; and

[0040] FIG. 2 is a block diagram showing the flow of a method for a binaural hearing system for improving spatial auditory perception.

DETAILED DESCRIPTION OF THE INVENTION

[0041] Referring now in detail to the figures of the drawings, in which mutually corresponding parts and variables are each provided with the same reference signs, and first, particularly, to FIG. 1 thereof, there is seen a plan view diagrammatically showing a conversation situation in which a first person 1 is conversing with a second person 2 who is in front of the first person 1 (and is facing him or her). Diagonally behind the first person 1 is also a third person 3, who may also express or interject things, but is not taking part in the conversation between the first person 1 and the second person 2. For the explanations that follow, the third person 3 could also be replaced by another directional noise source of any kind whatsoever.

[0042] FIG. 1b uses a plan view to diagrammatically show the conversation situation shown in FIG. 1a. In this case, the first person 1 is provided by a wearer 5 of a binaural hearing system 10 based on the prior art, which includes a first hearing instrument 11 and a second hearing instrument 12. In particular, the hearing instruments 11, 12 may each be provided by a hearing device (“in the narrower sense”). According to the conversation situation shown in FIG. 1 a, the second person 2 is simultaneously an interlocutor 6 of the wearer 5. The third person 3 can be regarded as a source of interference 7 in connection with the conversation situation between the wearer 5 and his or her interlocutor 6.

[0043] A dynamic compression is normally applied to the input signals in hearing instruments in order to map the dynamic range that is fundamentally able to be resolved by the microphones of the hearing instruments (that is to say from the minimum registerable sound level through to overdrive) to a range that is acceptable and preferably agreeable to the wearer. The lower limit for this range is then preferably provided by the hearing threshold of the wearer, and the upper limit of the range is preferably provided by the discomfort threshold. This is intended in particular to ensure a respective optimum gain (or attenuation) for all possible or realistically foreseeable input levels at the microphones.

[0044] In the binaural hearing system 10 shown in FIG. 1b, the dynamic compression described is applied in the two hearing instruments 11, 12 independently of one another, i.e. for each of the two hearing instruments 11, 12 an AGC ascertains a respective optimum gain factor for the associated input signal. This gain factor is normally different for the two hearing instruments 11, 12, since e.g. a higher sound level is recorded at the second hearing instrument 12, which is worn on the right ear of the wearer 5 in the present case, due to the source of interference 7, than at the first hearing instrument 11 (which is worn on the left ear of the wearer 5 in the present case, and therefore the source of interference 7 is shadowed by the head of the wearer 5).

[0045] A dynamic compression involves a higher sound level being assigned a lower gain factor for the most part than a lower sound level, the rule of assignment being provided for example on the basis of a compression characteristic curve (which describes the input level/output level relationship). For the conversation situation shown in FIG. 1a or 1b, this means that the gain factor that is ascertained in the first hearing instrument 11 as a first instantaneous gain parameter G1 for application to the input signal there (or to the input signals there when there are multiple) is greater than a second instantaneous gain parameter G2 ascertained in the second hearing instrument 12 for application there.

[0046] Due to the different gain for the input signals of the two hearing instruments 11, 12 as a result of the instantaneous gain parameters G1, G2, the conversation contributions of the interlocutor 6 are thus also amplified to different degrees in the two hearing instruments 11, 12, and accordingly also reproduced with different loudnesses for the wearer 5. This results in the wearer perceiving the “left-hand” contributions of the interlocutor 6 (which are recorded and processed by the first hearing instrument 11) to be louder due to G1>G2, than the “right-hand” contributions (which are recorded and processed by the second hearing instrument 12).

[0047] However, during the corresponding reproduction of the input signals of the hearing instruments 11, 12, this distorts the interaural level differences that are used by the hearing system to locate sound sources. This can also distort location, i.e. the wearer may acoustically perceive a sound source to be at a different location in the room than the actual position of the sound source.

[0048] Thus, in the present example shown in FIG. 1b, if the source of interference 7 delivers a loud noise, the dynamic compression due to the increased sound level lowers the second instantaneous gain factor G2 (in comparison with when the source of interference 7 is silent), that is to say that the G1>G2 case described above arises. However, since the interlocutor 6 is in the frontal direction 14 in relation to the wearer 5, and therefore his or her conversation contributions arrive at the wearer 5 with the same loudness, these conversation contributions are reproduced more loudly by the first hearing instrument 11, which is worn on the left by the wearer 5, than by the second hearing instrument 12, which is worn on the right. The perception of the wearer 5 is that this “artificial” level difference due to the different gain is felt as a shadowing effect and therefore as an interaural level difference, which means that the interlocutor 6 is no longer “heard” in the frontal direction 14 (that is to say perceived there), but rather in a direction 15 that is rotated slightly to the left from the frontal direction 14. This is illustrated diagrammatically in FIG. 1b on the basis of a graphical shift of the interlocutor 6 (see broad arrow) in the direction 15.

[0049] The different volumes due to the different instantaneous gain parameters G1>G2 can also have the same effect on other sound sources in the surroundings of the wearer 5. This also applies to the source of interference 7 in particular. In realistic situations, such a source of interference may also be provided by a danger to the wearer 5 (e.g. by an approaching vehicle in road traffic), which is why spatially distorted perception is also serious for safety reasons.

[0050] In order to overcome the problem described on the basis of FIG. 1b, a method is provided for the binaural hearing system 10, the flow of which is shown in a block diagram on the basis of FIG. 2. The first hearing instrument 11 has an electroacoustic first input transducer M1 that is configured to generate a first input signal E1 from ambient sound 18, and which is provided by a microphone in the present case. The first hearing instrument 11 can also have a further input transducer (not shown) that is used to generate a further input signal from ambient sound 18, with the result that a directional processing of the local input signals can be performed in the hearing instrument 11.

[0051] The second hearing instrument 12 has an electroacoustic second input transducer M2 that is configured to generate a second input signal E2 from the ambient sound 18, and which is likewise provided by a microphone in the present case. The second hearing instrument 12 can also have a further input transducer (not shown) for a local directional processing in this case.

[0052] The first input signal E1 is used to generate a first transmission signal T1, which is transmitted from the first hearing instrument 11 to the second hearing instrument 12. The first transmission signal can be generated e.g. from a frequency range of contiguous frequency bands of the first input signal E1 in this instance. In the aforementioned case of a directional processing of two input signals in the first hearing instrument 11, the first transmission signal may also be provided by the resultant directional signal (or frequency bands thereof). The first transmission signal T1 may also be provided directly by the complete first input signal E1, however. Analogously to this, the second input signal E2 is used to generate a second transmission signal T2, which is transmitted from the second hearing instrument 12 to the first hearing instrument 11.

[0053] In the first hearing instrument, the first input signal E1 is used by a first local AGC 21-L, frequency band by frequency band, to ascertain a first instantaneous gain parameter G1 for the first input signal E1. This can preferably be ascertained in such a way that the first instantaneous gain parameter G1 attains an optimum gain, with respect to the dynamic range of the hearing instrument 11 and the hearing of the wearer 5, for the ambient sound 18 represented in the first input signal E1. Similarly, a first remote AGC 21-R in the first hearing instrument 11 uses the second transmission signal T2, frequency band by frequency band, to locally ascertain a second instantaneous gain parameter G2 for the second input signal E2 according to the same rules as the first instantaneous gain parameter G1 on the basis of the first input signal E1. The second instantaneous gain parameter G2 therefore forms the optimum gain for the second input signal E2 in the respective frequency band with respect to the dynamic range and the hearing capacity of the wearer 5.

[0054] It should be noted in this case that, in the present example, the second input signal E2 is identical to the second transmission signal T2 in the frequency bands in question (that is to say in those in which T2 is different than zero anyway). In the case of two input signals per hearing instrument, each locally preprocessed to produce corresponding directional signals, which is not shown, the directional signals, which are each generated locally, preferably replace the two input signals E1, E2. This means in particular that the instantaneous gain parameters G1, G2 are preferably generated from the applicable directional signals frequency band by frequency band (the respective directional signal, if necessary limited to a few frequency bands thereof, in particular also being used as a transmission signal).

[0055] Analogously, in the second hearing instrument 12, a second local AGC 22-L uses the second input signal E2 to ascertain the second instantaneous gain parameter G2 and a second remote AGC 22-R uses the first transmission signal T1 to ascertain the first instantaneous gain parameter G1, frequency band by frequency band. Due to the signal components with identical frequency bands that are used in each of the two hearing instruments 11, 12 to ascertain the first or second instantaneous gain parameter G1, G2, and due to the identical algorithms in the local first AGC 21-L and the remote second AGC 22-R (and in the remote first AGC 21-R and the local second AGC 22-L), the respectively ascertained first instantaneous gain parameters G1 in the two hearing instruments 11, 12 are thus identical to one another (and the respectively ascertained second instantaneous gain parameters G2 are identical to one another).

[0056] Furthermore, the first input signal E1 and the second transmission signal T2 are now used in a first source determination unit Q1 of the first hearing instrument 11, frequency band by frequency band, to at least approximately determine a direction 25 of a sound source 30 in the ambient sound 18. This approximate determination can ascertain e.g. a polar angle (if applicable to within an accuracy of 5°, 10° or the like) of the sound source relative to the frontal direction 14, or can ascertain just a half-area relative to a plane of symmetry 28 of the binaural hearing system 10 that contains the frontal direction 14, in which the sound source 30 is located. This half-area in question will be referred to as the focus half-area 31 in this case. Analogously thereto, the at least approximate direction 25 is also ascertained, frequency band by frequency band, in a second source determination unit Q2 of the second hearing instrument 12 on the basis of the second input signal E2 and the first transmission signal T1. Since the same signal components in the frequency bands are used for this purpose in each of the first and second hearing instruments 11, 12 (i.e. the respective input signal E1 or E2 is identical to its transmission signal T1 or T2 in the frequency bands used), the identical direction 25 is ascertained in the two source determination units Q1, Q2. If two input signals, each locally preprocessed to produce corresponding directional signals, are present in each hearing instrument 11, 12, which is not shown, the directional signals for the frequency bands are preferably supplied to each of the first and second source determination units Q1, Q2.

[0057] The direction 25 is used in each of the two hearing instruments 11, 12 to ascertain the focus half-area 31 in which the sound source 30 is located (if this has not already been done by the approximate determination of the direction 25), and, as a result of this, the half-area opposite the focus half-area 31, which will be referred to as the background half-area 32 in this case.

[0058] The first and second instantaneous gain parameters G1, G2 and the knowledge of the focus half-area 31 are now used in the first hearing instrument 11 to make a first adjustment 41 to a first parameter P1 of the AGC that is used for the signal processing locally in the first hearing instrument 11 (i.e. in the present exemplary embodiment a “remote” parameter of the second hearing instrument 12 is not adjusted in the first hearing instrument 11). Additionally or alternatively thereto, a second adjustment 42 to a second parameter P2 of the AGC that is used for the signal processing locally in the first hearing instrument 12 is made in the second hearing instrument 12.

[0059] In the present case, the first parameter P1 is provided by the first instantaneous gain parameter G1, and the second parameter P2 is provided by the second instantaneous gain parameter G2. If for example G1<G2 (if e.g. the sound source 30 in the focus half-area 31, due to shadowing effects, results in a higher sound level than in the background half-area 32, and there is also no excessively loud source of interference there), then for example the adjustment can take place in the second adjustment 42 simply using the value of the first instantaneous gain parameter G1 for the second parameter P2, with the result that the gain for the input signals E1, E2 is the same in both hearing instruments 11, 12. Such lowering merely attenuates additional background noise in the background half-area 32. If, conversely, G1>G2 (e.g. due to a loud source of interference in the background half-area 32 given a simultaneous useful signal from the sound source 30), then adaptive alignment of the parameters P1, P2 (that is to say of the two instantaneous gain parameters G1, G2) can be performed on the basis of additional voice recognition (not shown) for the input signals E1, E2 (or the transmission signals T1, T2). In short signal portions (for example frames, or other time bins of suitable length) containing voice components, the adjustment may be interrupted in order to prevent the voice signal from being incomprehensible as a result of G2 being raised (amplification of the background noise) or G1 (and thus the voice signal) being lowered. The adjustment (e.g. by aligning the instantaneous gain parameters G1, G2 for the values of the parameters P1, P2) is then restricted to the cases in which there is no voice signal.

[0060] Other, previously described, types of adjustments—in particular of both parameters P1 and P2 simultaneously—can also be carried out in this case.

[0061] The first input signal E1 is then processed further in the first hearing instrument 11 using the appropriately adjusted first parameter P1 to produce a first output signal Ou1, and the second input signal E2 is processed further in the second hearing instrument 12 using the appropriately adjusted second parameter P2 to produce a second output signal Ou2 (wherein, as mentioned, the adjustment may have a nontrivial effect only on one of the two parameters). The two output signals Out, Ou2 can then also be subjected to further signal processing steps, not shown in more detail (e.g. additional rejection of noise and/or acoustic feedback or the like), and are subsequently each converted by an electroacoustic first or second output transducer L1 or L2 into a first or second output sound signal 51 or 52, respectively.

[0062] Although the invention has been illustrated and described more thoroughly in detail by way of the preferred exemplary embodiment, the invention is not limited by the examples disclosed and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

[0063] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

LIST OF REFERENCE SIGNS

[0064] 1 first person [0065] 2 second person [0066] 3 third person [0067] 5 wearer (of the binaural hearing system) [0068] 6 interlocutor [0069] 7 source of interference [0070] 10 binaural hearing system [0071] 11 first hearing instrument [0072] 12 second hearing instrument [0073] 14 frontal direction [0074] 15 direction [0075] 18 ambient sound [0076] 21-U-R first local or remote AGC [0077] 22-L/-R second local or remote AGC [0078] 25 direction (of the sound source) [0079] 28 plane of symmetry [0080] 30 sound source [0081] 31 focus half-area [0082] 32 background half-area [0083] 41 first adjustment [0084] 42 second adjustment [0085] 51 first output sound signal [0086] 52 second output sound signal [0087] E1, E2 first and second input signals [0088] G1, G2 first and second instantaneous gain parameters [0089] L1, L2 (electroacoustic) first and second output transducers [0090] M1, M2 (electroacoustic) first and second input transducers [0091] Ou1, Ou2 first and second output signals [0092] P1, P2 first and second parameters (of an AGC) [0093] Q1, Q2 first and second source determination units [0094] T1, T2 first and second transmission signals