METHOD FOR OPERATING A BINAURAL HEARING SYSTEM AND BINAURAL HEARING SYSTEM

Abstract

In a method for operating a binaural hearing system having a first hearing aid and a second hearing, the first hearing aid generates a first reference signal from a sound signal by a first reference microphone and the second hearing aid generates a second reference signal from the sound signal by a second reference microphone. The first reference signal and the second reference signal are both used to derive a first binaural beamformer signal. For at least a number of frequency bands, the first reference signal is used to derive a first phase. For the number of frequency bands, a first output signal is derived from the first binaural beamformer signal and the first phase.

Claims

1. A method for operating a binaural hearing system, the binaural hearing system having a first hearing aid and a second hearing aid, which comprises the steps of: generating in the first hearing aid, a first reference signal, from a sound signal received by a first reference microphone; generating in the second hearing aid, a second reference signal, from the sound signal received by a second reference microphone; using both the first reference signal and the second reference signal to derive a first binaural beamformer signal; using the first reference signal to derive a first phase for at least a number of frequency bands; and deriving a first output signal from the first binaural beamformer signal and the first phase for the number of frequency bands.

2. The method according to claim 1, which further comprises: using both the first reference signal and the second reference signal to derive a second binaural beamformer signal; using the second reference signal to derive a second phase for at least a further number of frequency bands; and deriving a second output signal from the second binaural beamformer signal and the second phase for the further number of frequency bands.

3. The method according to claim 1, wherein: in the number of frequency bands, the first binaural beamformer signal is decomposed into its magnitude and phase components; and the first output signal is derived using the magnitude component of the first binaural beamformer signal and the first phase.

4. The method according to claim 3, wherein in the number of frequency bands, a magnitude component of the first output signal is given by the magnitude component of the first binaural beamformer signal, and the phase component of the first output signal is given by the first phase.

5. The method according to claim 1, which further comprises generating a first supplementary signal from the sound signal received by a first supplementary microphone in the first hearing aid.

6. The method according to claim 5, which further comprises using the first reference signal and the first supplementary signal to derive the first phase.

7. The method according to claim 6, wherein: from the first reference signal and from the first supplementary signal, a first pre-processed signal is derived; and in the number of frequency bands, the first phase is given by a phase of the first pre-processed signal.

8. The method according to claim 7, which further comprises using the first pre-processed signal for obtaining the first binaural beamformer signal.

9. The method according to claim 1, which further comprises generating in the second hearing aid, a second supplementary signal from the sound signal received by a second supplementary microphone.

10. The method according to claim 9, which further comprises deriving from the second reference signal and from the second supplementary signal, a second pre-processed signal.

11. The method according to claim 10, which further comprises using the second pre-processed signal for obtaining the first binaural beamformer signal.

12. A binaural hearing system, comprising: a first hearing aid having a first reference microphone; a second hearing aid having a second reference microphone; and a signal processor programmed to: generate in said first hearing aid, a first reference signal, from a sound signal received by said first reference microphone; generate in said second hearing aid, a second reference signal, from the sound signal received by said second reference microphone; use both the first reference signal and the second reference signal to derive a first binaural beamformer signal; use the first reference signal to derive a first phase for at least a number of frequency bands; and derive a first output signal from the first binaural beamformer signal and the first phase for the number of frequency bands.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0029] FIG. 1 is schematical top view of a conversation hearing situation including a user of a state of the art binaural hearing system and five speakers;

[0030] FIG. 2 is a schematical top view of the conversation hearing situation according to FIG. 1, as well as an acoustical localization of the speakers as perceived by the user of the binaural hearing system;

[0031] FIG. 3 is a block diagram of a method for operating a binaural hearing system in order to preserve perception of binaural cues when noise reduction is active; and

[0032] FIG. 4 is a schematical top view of the conversation hearing situation given in FIG. 1, as well as the acoustical localization of the speakers as perceived by the user of the binaural hearing system when applying the method according to FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Parts and variables corresponding to one another are provided with in each case the same reference numerals in all figures.

[0034] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a schematical top view of a hearing situation 1 corresponding to a conversation is shown. A user 2 of a non-illustrated state-of-the-art binaural hearing system is surrounded by his conversational partners, given by speakers 4, 6, 8, 10, 12, while directing his view towards the target speaker 4 for a given moment.

[0035] If the state-of-the-art binaural hearing system is applying noise reduction in which noise from directions other than the one of the target speaker 4, at least partially, is aimed to be reduced via the binaural beamforming of the binaural beamforming system, the target speaker 4 will be perceived by the user 2 in the proper direction. However, the other, non-target speakers 6, 8, 10, 12, apart from having an attenuated signal volume in the output signal of the binaural beamforming hearing aid as perceived by the user 2, due to the binaural beamforming may show their binaural cues distorted when talking to the user 2 which is focused on the target speaker 4, leading to an improper perception of the acoustical localization of the non-target speakers 6, 8, 10, 12 in the perception of the user 2.

[0036] This is displayed schematically in FIG. 2. The attenuation of the signal volume of—possibly occasional—conversational contributions of the non-target target speakers 6, 8, 10, 12 with respect to the signal volume of the contributions of the target speaker 4 in the output signal of the binaural hearing system is displayed by a miniaturization of the non-target speakers 6, 8, 10, 12 compared to FIG. 1. The loss of the binaural cues may lead to a wrong acoustical perception of the positions of the non-target speakers 6, 8, 10, 12 by the user 2. This means, the user 2 can see the actual positions of two intervening non-target speakers 6, 12 as spatially well separated from the target speaker 4, but due to the state-of-the-art binaural beamforming, displayed by the beam 14, and the loss of binaural cues of the non-target speakers 6, 12 caused by the noise reduction processes, the user 2 “hears” contributions from the non-target speakers 6, 12 as if those were located much closer to the target speaker 4.

[0037] In FIG. 3, a method 18 for operating a binaural hearing system 20 is illustrated by means of a block diagram. The method 18 is particularly useful in order to preserve binaural cues of a sound signal 22 when noise reduction is active in the binaural hearing system 20. The binaural hearing system 20 has a first hearing aid 24 and a second hearing aid 26. In the first hearing aid 24, a first reference signal 28 is generated from the sound signal 22 by a first reference microphone 30, while a first supplementary signal 32 is generated from the sound signal 22 by a first supplementary microphone 34. In the second hearing aid 26, a second reference signal 36 is generated from the sound signal 22 by a second reference microphone 38, while a second supplementary signal 40 is generated from the sound signal 22 by a second supplementary microphone 42. From the first reference signal 28 and the first supplementary signal 32, a first pre-processed signal 44 is generated, employing pre-processing such as, e.g., frequency band filtering, monaural noise reduction and feedback cancellation. The exact pre-processing techniques applied in order to obtain the first pre-processed signal 44 from the first reference signal 28 and the first supplementary signal 32 may vary over different frequency bands. From the second reference signal 36 and the second supplementary signal 40, a second pre-processed signal 46 is generated in a similar way.

[0038] Now in both the first hearing aid 24 and the second hearing aid 26, a binaural beamforming process 48 is preformed, taking for each hearing aid the first pre-processed signal 44 and the second pre-processed signal 46 as bandwise input signals, and generating a first binaural beamformer signal 50 in the first hearing aid 24 and a second binaural beamformer signal 52 in the second hearing aid 52, respectively. The first and the second binaural beamformer signal 50, 52 each may show a spatial characteristics determined by signal components of all of the first and second reference and supplementary signals, thus opening the way to a very efficient noise reduction and speaker enhancement by a narrow beamforming. The spatial characteristics for the first binaural beamformer signal 50 may vary over different frequency bands, and likewise for the second binaural beamformer signal 52.

[0039] Thus, the first and second binaural beamformer signals 50, 52, respectively, may show a very good SNR for a given target signal, as well as a very well defined, narrow beam. However, for non-target sound signals whose sound source lies outside of the beam's direction, the beamforming distorts the binaural cues such that the spatial location of the non-target sound source would be perceived wrong by the user 2 of the binaural hearing system 20, e.g. closer to the target sound source, as described in FIG. 2. To this end, the binaural cues are restored by the method 18 before generating an output signal that is output by a loudspeaker of a hearing aid.

[0040] In the first hearing aid 24, a first phase 54 is tapped off from the first pre-processed signal 44. The first binaural beamformer signal 50 is decomposed into its magnitude 56 and its phase 58, and for certain frequency bands, preferably for at least a number of frequency bands below 2 kHz, the phase 58 of the first binaural beamformer signal 50 is substituted by the first phase 54. For other frequency bands, in particular for at least some bands above 2 kHz, no such substitution is performed. After the reconstruction 60 of the binaural cues by plugging the first phase 54—given by the phase of the first pre-processed signal 44—into the first binaural beamformer signal 50 in the corresponding frequency bands while maintaining the magnitude 56 of the first binaural beamformer signal 50, the resulting signal of the reconstruction 60 is defined as a first output signal 62. The first output signal 62 may be treated by applying further non-directional sound processing (not shown) before outputting it via some first loudspeaker (not shown) of the first hearing aid 24 to one hearing of the user 2. For some frequency bands, in particular frequency bands above 2 kHz, the reconstruction 60 may not be necessary, and the first output signal 62 may directly be given by the first binaural beamformer signal 50.

[0041] The reconstruction 70 of the binaural cues in the second hearing aid 26 is performed in a similar way to the reconstruction 60 in the first hearing aid 24. The second binaural beamformer signal 52 is decomposed into its phase 72 and its magnitude 74, and a second phase 76 is extracted from the second pre-processed signal 46. In at least a number of frequency bands—some of them preferably below 2 kHz—the second phase 76 is plugged into the decomposition of the second binaural beamformer signal 52, substituting the phase 72 of the latter. The second output signal 78 in the corresponding frequency bands in which the reconstruction 70 is performed is given by the magnitude 74 of the second binaural beamformer signal 52 with the second phase 76.

[0042] For the first output signal, when restoring the binaural cues via the reconstruction 60, the phase information for the first output signal 62 is entirely extracted from the first pre-processed signal 44, and thus, entirely determined by the phase of the sound signal 22 at the first hearing aid 24. On the one hand, a noise reduction process which is based on a binaural beamforming process suppressing sounds from sound sources located in different directions than the target sound source may distort the binaural cues of non-target sound signals, i.e., sound signal components whose source is not located in the target direction. Even though these sound signals are suppressed by the binaural beamforming anyway, and might not be perceived as “conversationally relevant”, they still might have an important impact on the user's 2 perception of the acoustical scene in his hearing environment. Distorted binaural cues of these non-target sound signals then may lead to a mismatch of the acoustical perception of the non-target sound sources and their actual positions as seen by the user. The phase information taken from one hearing aid as the phase in that hearing aid's output signal allows the user 2 to perceive the proper temporal shiftings and delays in order to restore binaural cues.

[0043] Thus, as schematically shown in FIG. 4 in a top view of the hearing situation 1 given in FIG. 1, the user 2 now acoustically locates the non-target speakers 6, 12 in the same position with respect to the target speaker 4 as he sees them.

[0044] Even though the invention has been illustrated and described in detail with help of a preferred embodiment example, the invention is not restricted by this example. Other variations can be derived by a person skilled in the art without leaving the extent of protection of this invention.

[0045] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0046] 1 hearing situation [0047] 2 user (of a binaural hearing system) [0048] 4 target speaker [0049] 6-12 non-target speakers [0050] 14 beam [0051] 18 method for operating a binaural hearing system [0052] 20 binaural hearing system [0053] 22 sound signal [0054] 24 first hearing aid [0055] 26 second hearing aid [0056] 28 first reference signal [0057] 30 first reference microphone [0058] 32 first supplementary signal [0059] 34 first supplementary microphone [0060] 36 second reference signal [0061] 38 second reference microphone [0062] 40 second supplementary signal [0063] 42 second supplementary microphone [0064] 44 first pre-processed signal [0065] 46 second pre-processed signal [0066] 48 binaural beamforming process [0067] 50 first binaural beamformer signal [0068] 52 second binaural beamformer signal [0069] 54 first phase [0070] 56 magnitude of the first binaural beamformer signal [0071] 58 phase of the first binaural beamformer signal [0072] 60 reconstruction [0073] 62 first output signal [0074] 70 reconstruction [0075] 72 phase of the second binaural beamformer signal [0076] 74 magnitude of the second binaural beamformer signal [0077] 76 second phase [0078] 78 second output signal