METHOD FOR DIRECTIONAL SIGNAL PROCESSING FOR A HEARING AID AND HEARING SYSTEM

Abstract

A method for directional signal processing for a hearing aid includes generating first and second input signals from an ambient sound signal using first and second input transducers of the hearing aid and forming first and second directional signals based on the input signals. The directional signals have relative attenuations in directions of first and second useful signal sources. First and second amplification parameters for amplification of first and second useful signals of the signal sources are ascertained. A reference directional characteristic is defined for a reference directional signal. Based on the amplification parameters as a function of the reference directional characteristic, corrected first and second amplification parameters are ascertained so that an output directional signal, formed as a sum of the directional signals weighted by using the corrected amplification parameters, merges into a linearly scaled reference directional signal, if the first and second amplification parameters are equal.

Claims

1. A method for directional signal processing for a hearing aid, the method comprising: generating a first input signal from a sound signal of the surroundings by using a first input transducer of the hearing aid; generating a second input signal from the sound signal of the surroundings by using a second input transducer of the hearing aid; forming each of a first directional signal and a second directional signal based on the first input signal and the second input signal; providing the second directional signal with a relative attenuation in a direction of a first useful signal source; providing the first directional signal with a relative attenuation in a direction of a second useful signal source; ascertaining a first amplification parameter for an amplification of a first useful signal of the first useful signal source and a second amplification parameter for an amplification of a second useful signal of the second useful signal source; defining a reference directional characteristic for a reference directional signal; based on at least one of the first amplification parameter or the second amplification parameter as a function of the reference directional characteristic, ascertaining a corrected first amplification parameter and a corrected second amplification parameter, causing an output directional signal, formed as a sum of the first directional signal weighted by using the first corrected first amplification parameter and the second directional signal weighted by using the corrected second amplification parameter, to merge into a linearly scaled reference directional signal upon the first amplification parameter being equal to the second amplification parameter; and at least one of the corrected first or second amplification parameters being different from the corresponding underlying amplification parameter.

2. The method according to claim 1, which further comprises at least one of: ascertaining the corrected second amplification parameter in such a way that the second useful signal is amplified by the second amplification parameter in relation to the reference directional characteristic by way of the output directional signal, or ascertaining the corrected first amplification parameter in such a way that the first useful signal is amplified by the first amplification parameter by way of the output directional signal in relation to the reference directional characteristic.

3. The method according to claim 1, which further comprises: forming the corrected second amplification parameter as a product of the second amplification factor and a correction factor; and the correction factor corresponding to a linear coefficient of the second directional signal in a representation of the reference directional signal as a linear combination of the first directional signal and the second directional signal.

4. The method according to claim 1, which further comprises ascertaining the corrected first amplification parameter as the first amplification parameter when the first directional signal has its minimal sensitivity in a direction of the second useful signal source.

5. The method according to claim 1, which further comprises: forming a first intermediate signal and a second intermediate signal based on the first input signal and the second input signal; and at least one of: forming the first directional signal as a superposition of the first intermediate signal with the second intermediate signal, and simultaneously ascertaining an associated first superposition parameter, or forming the second directional signal as a superposition of the second intermediate signal with the first intermediate signal, and simultaneously ascertaining an associated second superposition parameter.

6. The method according to claim 1, which further comprises: forming the corrected first amplification parameter as a product of the first amplification factor and a first correction factor; and forming the corrected second amplification parameter as a product of the second amplification factor and a second correction factor.

7. The method according to claim 5, which further comprises: forming the corrected first amplification parameter as a product of the first amplification factor and a first correction factor; forming the corrected second amplification parameter as a product of the second amplification factor and a second correction factor; defining a first reference superposition parameter and a second reference superposition parameter for a superposition of the first intermediate signal and the second intermediate signal, forming the reference directional signal; and at least one of: forming the first correction factor based on a product of the second superposition parameter with the second reference superposition parameter, or forming the second correction factor based on a deviation of a product of the first superposition parameter with the first reference superposition parameter from the second reference superposition parameter.

8. The method according to claim 6, which further comprises forming the output directional signal based on the first directional signal weighted by using the corrected first amplification parameter and based on the second directional signal weighted by using the corrected second amplification parameter.

9. The method according to claim 6, which further comprises: ascertaining a first effective superposition parameter and a second effective superposition parameter based on the first and the second superposition parameters, the first and the second reference superposition parameters, and based on the first and second amplification parameters; and forming the output directional signal based on a superposition of the first intermediate signal weighted by using the first effective superposition parameter and the second intermediate signal weighted by using the second effective superposition parameter.

10. The method according to claim 9, which further comprises forming the first effective superposition parameter from the first reference superposition parameter, when the second directional signal is given by the second intermediate signal.

11. The method according to claim 6, which further comprises: ascertaining a second effective superposition parameter based on the first superposition parameter, based on the corrected first amplification parameter, and based on the corrected second amplification parameter; and forming the output directional signal based on a superposition of the first intermediate signal weighted by using the first effective superposition parameter and the second intermediate signal weighted by using the second effective superposition parameter.

12. The method according to claim 11, which further comprises forming the second effective superposition parameter from the first superposition parameter and a ratio of the corrected second amplification parameter and the first amplification parameter, when the second directional signal is given by the second intermediate signal.

13. The method according to claim 1, which further comprises selecting the reference directional characteristic of the reference directional signal as an omnidirectional directional characteristic or selecting the reference directional characteristic of the reference directional signal to simulate a shading effect of the human ear.

14. A hearing system, comprising: a hearing aid having a first input transducer for generating a first input signal from a sound signal of the surroundings and a second input transducer for generating a second input signal from the sound signal of the surroundings; and a control unit configured to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0063] FIG. 1 is a top-plan view illustrating a conversation situation of a wearer of a hearing aid with two conversation partners;

[0064] FIG. 2 is a schematic and block diagram illustrating preferred directional signal processing for the hearing aid in the conversation situation according to FIG. 1;

[0065] FIG. 3A is a top-plan view illustrating a directional characteristic of an output signal resulting from the directional signal processing according to FIG. 2; and

[0066] FIG. 3B is a top-plan view illustrating a directional characteristic of an alternative output signal resulting from the directional signal processing according to FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0067] Referring now in detail to the figures of the drawings, in which parts and dimensions corresponding to one another are each provided with the same reference signs, and first, particularly, to FIG. 1 thereof, there is seen a diagrammatic top view of a wearer 1 of a hearing aid 2, who is in a conversation situation with a first conversation partner 4 and a second conversation partner 8. The first conversation partner 4 is positioned in a first direction 6 with respect to the wearer 1, the second conversation partner 8 in a second direction 10 relative to the wearer 1. The first conversation partner 4 is the main conversation partner of the wearer 1 in this case, the second conversation partner 8 only participates in this conversation by way of isolated speech contributions. The described conversation situation is identical in this case for the top image and the bottom image of FIG. 1. The speech contributions of the first conversation partner 4 in this case form a first useful signal S1, and the speech contributions of the second conversation partner 8 form a second useful signal S2.

[0068] In order to then moderate the level peaks of the first useful signal S1 and the second useful signal S2 for the wearer 1 of the hearing aid 2 in an output sound signal of the hearing aid 2, as shown in the top image of FIG. 1, first a directional signal Xr1 is generated by using adaptive directional microphonics in such a way that this signal has a maximum and preferably complete attenuation in the second direction 10, in which the second conversation partner 8 is positioned. This means that the useful signal S2 is not acquired by the first directional signal Xr1. A compression factor which is thus calculated on the basis of the first directional signal Xr1 therefore reacts with respect to the two useful signal sources 14, 18, which are given by the first and second conversation partner 4 and 8, respectively, only to the first. A first amplification factor G1, which is ascertained in this case, determines the optimum signal amplification and thus implicitly also a corresponding compression ratio with respect to the first useful signal S1 of the first useful signal source 14 (thus of the first conversation partner 4) for each moment.

[0069] In the bottom image of FIG. 1, similarly to the top image, a second directional signal Xr2 in the same hearing situation is shown, which has a maximum and preferably complete attenuation in the first direction 6, thus the direction of the first conversation partner 4. Since the first direction 6 coincides with the frontal direction of the wearer 1, the second directional signal Xr2 is formed as a rear-directed cardioid directional signal Xa. The second amplification parameter G2, which is ascertained on the basis of the second directional signal Xr2 and assigned thereto, thus in each moment represents the optimum amplification with respect to the second useful signal S2 and in particular an associated compression ratio.

[0070] In an output sound signal of the hearing aid 2 for its wearer 1, to now be able to reduce the level peaks due to the conversation contributions of both the first conversation partner 4 and also the second conversation partner 8 to a level pleasant to the wearer 1 by using compression, on one hand, such an output signal could be formed from a linear combination of the first and the second directional signals Xr1, Xr2, which are each weighted using their corresponding amplification parameters G1, G2. Since the first directional signal Xr1 is also formed by using adaptive directional microphonics on the basis of a forward-directed cardioid directional signal and on the basis of the rear-directed cardioid directional signal Xa, such a linear combination would result in an output sound signal, the directional characteristic of which is similar in shape to that of the first directional signal Xr1, wherein a notch 22 of the maximum attenuation is shifted away from the second direction 10, however. This results on one hand in a possibly undesired, completely “deaf” region beyond the second useful signal source 18, which on the other hand can also fluctuate in its alignment as a result of the dependence of such a linear combination on the speech contributions of the first conversation partner 4.

[0071] FIG. 2 schematically shows, in a block diagram, a method for directional signal processing for the hearing aid 2 according to FIG. 1 in the situation described therein, which in particular is to moderate the level peaks of the two useful signals S1, S2 of the useful signal sources 14, 18 given by the respective conversation partner 4, 8. A first input transducer 24 and a second input transducer 26, which are disposed in the hearing aid 2, respectively generate a first input signal E1 or a second input signal E2 from a sound signal 28. The sound signal 28 is the ambient sound in this case, which thus also includes the first and the second useful signals S1, S2. A possible preprocessing, for example, A/D, conversion, or the like, is already to be included in this case in the input transducers 24, 26, which moreover each have a preferably omnidirectional microphone.

[0072] The first input signal E1 is now superimposed with the second input signal E2, which was delayed by a first delay parameter T1, and a first intermediate signal Z1 is formed therefrom. Similarly thereto, the second input signal E2 is superimposed with the first input signal E1, which was delayed by a second delay parameter T2, and a second intermediate signal Z2 is formed in this way. In the present case and without restriction of the generality, the first and the second delay parameters T1, T2 are each identical (T1=T2) and in addition are selected in such a way that the first intermediate signal Z1 is given by a forward-directed cardioid directional signal Xc, and the second intermediate signal Z2 by the rear-directed cardioid directional signal Xa. The first directional signal Xr1=Z1+a1.Math.Z2 according to FIG. 1 is now generated on the basis of the first intermediate signal Z1 and the second intermediate signal Z2 by using adaptive directional microphonics 40 with determination of a first superposition parameter a1 in such a way that the contributions of the second conversation partner 8, thus the second useful signal S2, are maximally suppressed in the first directional signal Xr1. The first amplification parameter G1 is ascertained for the first useful signal S1 on the basis of the first directional signal Xr1. The ascertained first amplification parameter G1 thus represents the optimum amplification and compression of the signal contributions of the first conversation partner 4 by the first directional signal Xr1.

[0073] Through the use of adaptive directional microphonics 42, the second directional signal Xr2, which maximally suppresses the contributions of the first conversation partner 4, thus the second useful signal S2, can be generated from the first intermediate signal Z1 and the second intermediate signal Z2. Since this conversation partner presently stands in the frontal direction in relation to the wearer 1, as already mentioned, the second directional signal Xr2 is given by the rear-directed cardioid directional signal Xa. The second directional signal Xr2 can be assumed in this case permanently as the rear-directed cardioid directional signal Xa, on one hand. On the other hand, a position change of the first conversation partner 4 can also be taken into consideration by using the adaptive directional microphonics 42 for the formation of the second directional signal Xr2 from the first and the second intermediate signal Z1, Z2.

[0074] Similarly to the first amplification parameter G1, the second amplification parameter G2 is furthermore determined on the basis of the second directional signal Xr2. This represents the optimum amplification and compression of the second useful signal S2 by the second directional signal Xr2.

[0075] In addition, a reference directional characteristic 63 is defined for a reference directional signal Xref. The reference directional signal Xref results in this case as a superposition from the two intermediate signals Z1, Z2 as

Xref=aref1.Math.Z1+aref2.Math.Z2

[0076] with an associated first reference superposition parameter aref1 and a second reference superposition parameter aref2, which are selected so that the reference directional signal Xref has the desired reference directional characteristics 63, thus, for example, simulates the spatial filter effect of the pinna on a human ear, in particular with respect to frequency band. An omnidirectional directional characteristic can also be selected for the reference directional signal Xref (which loses its directional effect in this way) for some or all frequency bands. The reference directional signal Xref is used in this case for the definition of the reference directional characteristic 63 and the reference superposition parameters aref1, aref2, and in the present case does not necessarily have to be generated as an independent signal from the two intermediate signals Z1 and Z2 (correspondingly shown by dashed lines); the reference superposition parameters aref1, aref2 can rather be defined beforehand. In particular, aref1=1 can be defined, so that the reference directional characteristic 63 of the reference directional signal Xref has no attenuation in the frontal direction.

[0077] For the following calculations, it is now taken into consideration that Xr2=Z2=Xa and therefore a2=0 applies, wherein moreover aref1=1 is set.

[0078] On the basis of the second amplification parameter G2, the first superposition parameter a1, and the reference superposition parameter aref2, a corrected second amplification parameter G2′ is now ascertained as

G2′=G2.Math.(aref2.Math.a1).

[0079] An output directional signal Xout is now formed on the basis of the first directional signal Xr1=Z1+a1.Math.Z2, weighted using the first amplification parameter G1, and on the basis of the second directional signal Xr2, which presently corresponds to the second intermediate signal Z2, weighted using the corrected second amplification parameter G2′, as

[00002]$\begin{array}{cc}\begin{array}{c}\mathrm{Xout}=G1.Math.\mathrm{Xr}1+G{2}^{\prime }.Math.Z2\\ =G1.Math.\left(Z1+a1.Math.Z2\right)+G2.Math.\left(\mathrm{aref}2-a1\right).Math.Z2.\end{array}& \left({\mathrm{xii}}^{\prime }\right)\end{array}$

[0080] If now, for example, the first useful signal S1 and the second useful signal S2 are equally loud in a frequency range, the same amplification parameter G1=G2 is thus assigned to each of them for this frequency range. In this case, in the output directional signal Xout, the contributions proportional to the first superposition parameter a1 mutually cancel out, and the output directional signal Xout merges into Xout=G1.Math.(Z1+aref2.Math.Z2), as in the reference directional signal Xref amplified (“scaled”) using G1.

[0081] Instead of the described generation of the output directional signal Xout on the basis of the first directional signal Xr1 and the rear-directed cardioid signal Xa as the second intermediate signal Z2, the output directional signal Xout may also be generated in that, on the basis of the first superposition parameter a1, on the basis of the corrected second amplification parameter G2′, and on the basis of the first amplification parameter G1, a first effective superposition parameter aeff1 and a second effective superposition parameter aeff2 are formed as

[00003]$\begin{array}{cc}\begin{array}{c}\mathrm{aeff}2=a1+G{2}^{\prime }/G1\\ =a1+\left(\mathrm{aref}2-a1\right).Math.G2/G1.\end{array}& \left(\mathrm{xiii}\right)\end{array}$

[0082] The first effective superposition parameter aeff1 has the value aeff1=1 in the present special case, but can also assume nontrivial values in particular for a2≠0. The correspondingly formed output directional signal

Xout=G1.Math.(aeff1.Math.Z1+aeff2.Math.Z2)

[0083] with aeff2 according to equation (xiv) and aeff1=1 then assumes the shape represented in equation (xii′). The output directional signal Xout has a directional characteristic in this case as a result of the present generation which has an amplification or attenuation by a factor G1 in the direction of the first useful signal source 14 (thus the direction of the first useful signal S1) in relation to the reference directional signal Xref, and has an amplification or attenuation by a factor G2 in the direction of the second useful signal source 18 (thus the direction of the second useful signal S2) in relation to the reference directional signal Xref (see also FIG. 3A and FIG. 3B in this regard).

[0084] Finally, on the basis of the output directional signal Xout, an output signal Yout is generated through signal processing steps 50, which in particular can include an additional frequency-band-dependent noise suppression, which output signal is converted by an output transducer 52 of the hearing aid 2 into an output sound signal 54.

[0085] In FIG. 3A, for the hearing situation of the wearer 1 shown in FIG. 1, a directional characteristic 60 of the output directional signal Xout generated as described in FIG. 2 is shown. The reference directional characteristic 62 (dashed line) is given in this case as an omnidirectional directional characteristic. For better clarity, the first amplification parameter G1 is selected as 0 dB in this case, while the second amplification parameter G2 is selected as −6 dB. The resulting directional characteristic 60 of the output directional signal Xout has a noticeable deviation from the omnidirectional reference directional characteristic 62 in the second direction 10 (thus the direction of the second useful signal source 18).

[0086] In FIG. 3B, instead of the omnidirectional reference directional characteristic 62, a reference directional signal Xref having a reference directional characteristic 64 is selected (dashed line), which models the filtering of the ambient sound by the pinna and corresponding shading effects. The first amplification parameter G1 is again selected in this case as 0 dB, while the second amplification parameter G2 is selected as −6 dB. The resulting directional characteristic 66 of the output directional signal Xout again has a noticeable deviation from the omnidirectional reference directional characteristic 64 in the direction of the second useful signal source 18, wherein an additional attenuation takes place in this direction due to the definition of the reference directional signal Xref, which is incorporated in the reference directional characteristic 64 as a result of the shading effects of the pinna.

[0087] Although the invention was illustrated and described in more detail by the preferred exemplary embodiment, the invention is not thus restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without leaving the scope of protection of the invention.

[0088] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0089] 1 wearer [0090] 2 hearing aid [0091] 4 first conversation partner [0092] 6 first direction [0093] 8 second conversation partner [0094] 10 second direction [0095] 14 first useful signal source [0096] 18 second useful signal source [0097] 22 notch [0098] 24 first input transducer [0099] 26 second input transducer [0100] 28 sound signal [0101] 40 adaptive directional microphonics [0102] 42 adaptive directional microphonics [0103] 50 signal processing steps [0104] 52 output transducer [0105] 54 output sound signal [0106] 60 directional characteristic [0107] 62 (omnidirectional) reference directional characteristic [0108] 63 reference directional characteristic [0109] 64 reference directional characteristic [0110] 66 directional characteristic [0111] a1 first superposition parameter [0112] aeff1 first effective superposition parameter [0113] aeff2 second effective superposition parameter [0114] aref1 first reference superposition parameter [0115] aref2 second reference superposition parameter [0116] E1 first input signal [0117] E2 second input signal [0118] G1 first amplification parameter [0119] G2 second amplification parameter [0120] G2′ corrected second amplification parameter [0121] S1 first useful signal [0122] S2 second useful signal [0123] T1 first delay parameter [0124] T2 second delay parameter [0125] Xa rear-directed cardioid signal [0126] Xc forward-directed cardioid signal [0127] Xout output directional signal [0128] Xr1 first directional signal [0129] Xr2 second directional signal [0130] Yout output signal [0131] Z1 first intermediate signal [0132] Z2 second intermediate signal