CA2479675C - Directional controller for a hearing aid - Google Patents
Directional controller for a hearing aid Download PDFInfo
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- CA2479675C CA2479675C CA002479675A CA2479675A CA2479675C CA 2479675 C CA2479675 C CA 2479675C CA 002479675 A CA002479675 A CA 002479675A CA 2479675 A CA2479675 A CA 2479675A CA 2479675 C CA2479675 C CA 2479675C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
- H04R25/40—Arrangements for obtaining a desired directivity characteristic
- H04R25/407—Circuits for combining signals of a plurality of transducers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
- H04R25/40—Arrangements for obtaining a desired directivity characteristic
- H04R25/405—Arrangements for obtaining a desired directivity characteristic by combining a plurality of transducers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2225/00—Details of deaf aids covered by H04R25/00, not provided for in any of its subgroups
- H04R2225/41—Detection or adaptation of hearing aid parameters or programs to listening situation, e.g. pub, forest
Abstract
Change-over of the sound receiving characteristic of a hearing aid having spaced apart first and second microphone means (Fmic, Bmic) between the omnidirectional characteristic and a directional characteristic is effected by controlled attenuation and time or phase delay of signals derived from the signals (X front, X back) from the first and second microphone means before forming and overall combined signal (y) to be supplied to the hearing aid signal processor, whereby the overall combined signal (Y) is determined by Y = X front * (1 - omni * e-j.omega.T) + X back * (omni - e -j.omega.T) , where omni is an adjustable attenuation control parameter preferably in the range 0 <= omni <= 1 and T is a time delay corresponding to the acoustical delay between the first and second microphone means. In result, the change between the omnidirectional characteristic and any desired form of the directional characteristic is effected as a smooth change-over substantially without affecting phase relationship. Time delay and amplitude characteristic of the hearing aid.
Description
A DIRECTIONAL CONTROLLER FOR A HEARING AID
This application is a division of Canadian Patent Application Serial No. 2,385,812, filed June 23, 2000.
In view of division enforced by the Canadian Intellectual Property Office the claims of this application are directed to a directional controller.
However, for the purpose of facilitating an understanding of all objects and features of the development which are 1o inextricably bound-up in one and the same inventive concept as taught and claimed in the parent application, the objects and teachings of those features claimed in the parent Canadian Application Serial No. 2,385,812 are retained herein.
~s Accordingly, in view of enforced division required by the Examiner in the prosecution of the aforesaid parent application, object clauses and features have been retained for the purposes of facilitating and understanding of the overall development. However, the 2o retention of any clauses or features which may be more particularly related to the parent application or a separate divisional thereof should not be regarded as rendering the teachings and claiming ambiguous or inconsistent with the subject matter defined in the 25 claims of the divisional application presented herein when seeking to interpret the scope thereof and the basis in this disclosure for the claims recited herein.
The present invention relates to a method for controlling the directionality of the sound receiving 3o characteristic of a hearing aid comprising spaced apart first and second sound receiving microphones.
This application is a division of Canadian Patent Application Serial No. 2,385,812, filed June 23, 2000.
In view of division enforced by the Canadian Intellectual Property Office the claims of this application are directed to a directional controller.
However, for the purpose of facilitating an understanding of all objects and features of the development which are 1o inextricably bound-up in one and the same inventive concept as taught and claimed in the parent application, the objects and teachings of those features claimed in the parent Canadian Application Serial No. 2,385,812 are retained herein.
~s Accordingly, in view of enforced division required by the Examiner in the prosecution of the aforesaid parent application, object clauses and features have been retained for the purposes of facilitating and understanding of the overall development. However, the 2o retention of any clauses or features which may be more particularly related to the parent application or a separate divisional thereof should not be regarded as rendering the teachings and claiming ambiguous or inconsistent with the subject matter defined in the 25 claims of the divisional application presented herein when seeking to interpret the scope thereof and the basis in this disclosure for the claims recited herein.
The present invention relates to a method for controlling the directionality of the sound receiving 3o characteristic of a hearing aid comprising spaced apart first and second sound receiving microphones.
Hearing aids having a directional sound receiving characteristic are useful to improve speech perception in noisy environments, where human speech may be received simultaneously from different directions, as is the case, e.g., in the noise environment frequently referred to as cocktail party noise.
With a directional sound receiving characteristic, e.g., in the shape of a cardioid or super cardioid characteristic, the speech perception in a hearing aid is to improved by reduced reception of sound coming from the back of the user, while maintaining the level of sound coming from the area in front of the user.
On the other hand, in environments with only low noise levels or no significant speech signals, the hearing aid user will normally prefer an omnidirectional or spherical sound receiving characteristic, offering the same perception of sound irrespective of the direction from which it arrives.
As will be further explained in the following, a 2o prior art hearing aid of the kind defined above, offering the possibility of changing the sound receiving characteristic between an omnidirectional characteristic and a directional characteristic of varying shape, has been disclosed in United States Patent No. 5,757,933.
With this prior art hearing aid operating only with an omnidirectional characteristic, the signal from the first microphone facing the area in front of the user is supplied to the signal processor. By manual operation of a switch, a signal derived from the second microphone 3o facing the rear of the user is subjected to inversion, followed by adjustable phase delay and adjustable attenuation. It is then combined via a summing node with the signal derived from the first microphone. When the sound receiving characteristic in a hearing aid of this type is changed or changes from the omnidirectional to a directional shape, the arrival time of the sound changes during the transition. This change of phase or time delay may become confusing for a binaural hearing aid system that uses a pair of separate hearing aids operating with 1o independent and automatic change of the sound receiving characteristic. When phase or arrival times change differently in the two hearing aids, the user's ability to locate the various sound sources in the surrounding space decreases, and the advantage of a binaural hearing aid system will be degraded.
Furthermore, the phase and time relationship in the hearing aid degrades the quality of the sound perceived by the user. It may sound like the result of a Doppler 2o effect.
At the same time, in hearing aids of this type the amplitude characteristic will also change during transition between the omnidirectional and a directional characteristic, e.g., from a flat response to a response in which the amplitudes of higher frequencies will be increased. This increase may be in the area of about 6 dB/octave. This results in a serious problem, in that hearing aids of this type cannot be perfectly fitted with an optimum transfer characteristic for both the omnidirectional and the directional characteristic.
With a directional sound receiving characteristic, e.g., in the shape of a cardioid or super cardioid characteristic, the speech perception in a hearing aid is to improved by reduced reception of sound coming from the back of the user, while maintaining the level of sound coming from the area in front of the user.
On the other hand, in environments with only low noise levels or no significant speech signals, the hearing aid user will normally prefer an omnidirectional or spherical sound receiving characteristic, offering the same perception of sound irrespective of the direction from which it arrives.
As will be further explained in the following, a 2o prior art hearing aid of the kind defined above, offering the possibility of changing the sound receiving characteristic between an omnidirectional characteristic and a directional characteristic of varying shape, has been disclosed in United States Patent No. 5,757,933.
With this prior art hearing aid operating only with an omnidirectional characteristic, the signal from the first microphone facing the area in front of the user is supplied to the signal processor. By manual operation of a switch, a signal derived from the second microphone 3o facing the rear of the user is subjected to inversion, followed by adjustable phase delay and adjustable attenuation. It is then combined via a summing node with the signal derived from the first microphone. When the sound receiving characteristic in a hearing aid of this type is changed or changes from the omnidirectional to a directional shape, the arrival time of the sound changes during the transition. This change of phase or time delay may become confusing for a binaural hearing aid system that uses a pair of separate hearing aids operating with 1o independent and automatic change of the sound receiving characteristic. When phase or arrival times change differently in the two hearing aids, the user's ability to locate the various sound sources in the surrounding space decreases, and the advantage of a binaural hearing aid system will be degraded.
Furthermore, the phase and time relationship in the hearing aid degrades the quality of the sound perceived by the user. It may sound like the result of a Doppler 2o effect.
At the same time, in hearing aids of this type the amplitude characteristic will also change during transition between the omnidirectional and a directional characteristic, e.g., from a flat response to a response in which the amplitudes of higher frequencies will be increased. This increase may be in the area of about 6 dB/octave. This results in a serious problem, in that hearing aids of this type cannot be perfectly fitted with an optimum transfer characteristic for both the omnidirectional and the directional characteristic.
In this background, it is the object of the present invention to provide a method of the kind defined, in which the deficiencies of the prior art hearing aid are addressed by effecting a change-over between the omnidirectional characteristic and any directional characteristic, substantially without changing the phase relationship or time delay and the amplitude characteristic of the signals. The change-over between the omnidirectional characteristic and a directional io characteristic and vice versa may be controllable or even automatic.
The present invention describes a method for controlling the directionality of the sound receiving characteristic of a hearing aid, comprising spaced apart first and second sound receiving microphone means, a signal processor for processing signals supplied by said microphone means and an output transducer for emission of sound signals in response to output signals from the signal processor, said method comprising the steps of 2o changing over said sound receiving characteristic between an omnidirectional characteristic and a directional characteristic and, while operating the hearing aid with said directional characteristic, combining the signals supplied by said first and second microphone means into an overall combined signal, an adjustable time or phase delay being imposed on at least one signal, wherein said change over of the sound receiving characteristic from the omnidirectional characteristic to the directional characteristic and vice versa is effected by controlling 3o the attenuation and the time or phase delay of signals derived from both of the signals (Xfront~ Xback) from the first and second microphone means before forming said overall combined signal (Y), according to an adjustable attenuation control parameter (omni) and a delay (T), 5 whereby said overall combined signal (Y) is determined by Y ° Xfro~t * (1 - omni * e''"T) ~' Xback * (omni - e''"T) , to change over the hearing aid between said omnidirectional characteristic and any desired form of said directional characteristic as a smooth change over substantially 1o without effecting phase relationship, time delay and amplitude characteristic of the hearing aid.
The present invention also describes a hearing aid with controllable directionality of its sound receiving characteristic, comprising spaced apart first and second sound receiving microphones means, a signal processor for processing signals supplied by said microphone means and an output transducer for emission of sound signals in response to output signals from the signal processor, and further comprising change-over 2o control means for change over of the sound receiving characteristic between an omnidirectional characteristic and a directional characteristic and combining means for combining of the signals from the first and second microphone means to provide an overall combined signal supplied to the signal processor, while operating the hearing aid with said directional characteristic, and adjustable time or phase delay means for producing a phase-delayed modification of at least one signal, wherein said change-over control means comprises 3o controllable attenuation means and controllable time or phase delay means acting on signals derived from the signals (Xf=ont~ Xback) from both of the first and second microphone means, respectively, said attenuation and phase delay means (1-3; 14, 15, 18, 19) being controlled for forming said overall combined signal (Y) according to an adjustable attenuation control parameter (omni) and a delay (T), whereby said overall combined signal (Y) is determined by Y = Xf=ont * (1 - omni * e'~"T) + Xback * (omni - e''"'') , to change over the hearing aid between said omnidirectional characteristic and any desired form of said directional characteristic as a smooth change over substantially without affecting phase relationship, time delay and amplitude characteristic of the hearing aid.
In an aspect of the present invention, there is provided a directional controller for a hearing aid for processing input signals from at least two spaced apart microphones for producing a combined output signal for further processing in the hearing aid, the directional controller comprising adjustable time delay means for 2o producing a time-delayed modification of at least one signal, and change-over control means for effecting a change-over between an omnidirectional mode and a directional mode, and further comprising a first controllable attenuator for processing a signal derived from the signal (Xpront) from the first microphone to output a first processed signal, a second controllable attenuator for processing a signal derived from the signal (Xback) from the second microphone to output a second processed signal, the adjustable time delay 3o means being adapted for delaying signals derived from the signals from both of the first and the second microphones and combining means connected to combine the processed and delayed signals with the output signal from the first microphone to generate the combined output signal, the change-over control means being connected to control the controllable attenuator.
In the following the invention will be further explained with reference to the accompanying illustrative example drawings, in which Fig. 1 is a schematic block diagram of the prior art hearing aid of United States Patent No. 5,757,933, Figs. 2 to 5 are graphic representations illustrating variations of the sound receiving characteristic of the hearing aid in fig. 1 between the omnidirectional characteristic and different directional shapes and concurrent variation of amplitude characteristics of the front and back microphones used therein, Fig. 6 shows a schematic arrangement of the front end of a hearing aid according to the present invention, Figs. 7 to 10 are graphic representations corresponding to the representations in figs.2 to 5 with respect to the hearing aid shown in Fig. 6, Fig. 11 shows a schematic arrangement of a hearing aid according to the present invention with a change-over controller, Fig. 12 shows a similar schematic arrangement of an embodiment of the present invention, Fig. 13 schematically shows a schematic arrangement providing a further improvement of the arrangement shown 3o in Fig. 6, and Fig. 14 shows a schematic arrangement providing a further development of a hearing aid according to the invention.
s In the prior art hearing aid . shown in Fig. 1, two non-directional microphone circuits include a front microphone MICF and a back microphone MICB. Whereas the output signal from the front microphone MICF is supplied directly to the hearing aid signal processor via a summing node SN, the signal from the back microphone is supplied to the summing node SN (i.e., via an inverter, an adjustable phase delay circuit, and an attenuator with adjustable gain) only by closure of a manually operated 1o switch SW, whereby the sound receiving characteristic of the hearing is changed from the omnidirectional characteristic of front microphone MICF to a directional characteristic of varying shape.
The combined signal Y formed at the summing node SN
1s with switch SW closed and supplied to the signal processor will thus be related to the signals Xfront and Xback from front and back microphones MICF and MICE, respectively, by the relation Y = Xfront " Xback * omni * e' j~''. Here, the adjustable parameter omni represents the 2o adjustable gain of the attenuator, whereas T represents the adjustable time delay corresponding to the difference in arrival time for sound signals received by the front and back microphones MICF and MICB, respectively.
The graphic representations in figs. 2 25 and 3 illustrate examples of the variation of the sound receiving characteristic of the hearing aid in figure 1 from the omnidirectional shape ND and various directional shapes D1 to D10, ranging from weak cardioid to super cardioid form for values of the adjustable 3o parameter omni ranging from 0 to 1, measured at lkHz and 100 Hz, respectively. The graphic representations in figs. 4 and 5 show the variation in the amplitude characteristics of the signals received from the areas in front and back of the hearing aid, respectively, for correspondingly varying values of the parameter omni. As will appear from these representations for this prior art hearing aid, the change-over between the omnidirectional characteristic and the various shapes of directional characteristic results in the desired gradual reduction in 1o gain or amplitude response for the signals received from the area behind the user. However, this is also accompanied by a significant change in gain or amplitude response for the signals received from the area in front of the user. Consequently, adjustment or fitting of the hearing aid to compensate for a user's specific hearing impairment in quiet surroundings (i.e., where use of the omnidirectional characteristic is preferred) will not provide optimum compensation when a change-over is made to a directional characteristic, (i.e., where use of the 2p hearing aid in a more noisy sound environment, such as a party, is preferred).
Fig. 6, shows the front end of a hearing aid, including a change-over controller for controlling change of the directionality of sound receiving characteristic of the hearing aid from the omnidirectional characteristic to a directional charac-1~
teristic, and vice versa. This change may be effected as a switch-over, or as a gradual and smooth change-over.
The front end of the hearing aid comprises at least two microphone circuits (e.g., a front microphone Fmic and s a back microphone Bmic) and possibly optional preprocessing circuits for the electrical output signals from the microphones. The distance between the two microphones may be as small as about 1 man or as wide as about a few cm.
1o The front end further contains at~ least two controllable amplifiers or attenuators l and 2, at least one time or phase delay device 3, and at least three combining circuits 4, 5, and 6. It is to be understood that the combining circuits may contain positive as well is as negative input terminals, so as to form adding or subtraction operations or combinations thereof.
In the structure, the back microphone Bmic is connected to the controllable amplifier or attenuator 1 and to a first adding circuit 4.
2o The front microphone Fmic is connected directly to the controllable amplifier or attenuator 2 and to a second adding circuit 6. The output of the controllable amplifier or attenuator 2 is further connected directly to a second input of the first adding circuit 4, whereas 2s the output of the controllable amplifier 1 is directly connected to a positive input of a subtraction circuit 5.
Preferably, a controllable delay device 3 is included between the output of the first adding circuit 4 and the 3o negative input of the subtraction circuit 5.
In the following description the adding and subtracting circuits will generally be referred to as combining circuits.
In operation, sound from the environment of the hearing aid is picked up by both the front microphone Gmic and the back microphone Bmic. The distance between the two microphones may be as small as about 1 mm and as s wide as about a few cm.
The output signal of the front microphone F~nic is supplied to the combining circuit 6. The output signal of the back microphone Bmic is supplied to the controllable attenuator or controllable amplifier 1, and the gain can io be controllably changed from zero to about one, i.e., from no amplification to substantially full amplification.
This change-over may be effected as a switch-over or as a controlled gradual change. This means that amplification between zero and about one can be controllably achieved.
i5 Any output signal from the front microphone EYnic is also supplied to a controllable attenuator or amplifier 2, and the amplification may controllably be changed from zero to about one, i.e., from no amplification to substantially full amplification. Also in this case, the 2o change-over may be effected as a switch-over or as a gradual controlled change. This means that amplification between zero and about one may be achieved.
Any output signal from the controllable attenuator or amplifier 2 is supplied to a second input of the combining 2s circuit 4. Any output signal of combining circuit 4 is supplied to the controllable delay device 3, and the delay may be controlled from as small as about 1 us up to about 1000 us or more.
Any output signal of delay device 3 is supplied to 3o the negative input of combining circuit 5, and the output is supplied to the second input of the combining circuit 6.
Thereby, the output signal of the front microphone F~nic rnay be attenuated in the attenuator or controllable amplifier 2 before it is added to the undelayed output signal of the back microphone Bmic in the combining s circuit 4, the output signal of which is then delayed in delay device 3 before being supplied to the combining circuit 5. The controllable delay of delay device 3 will usually have the same value as the acoustical delay between the arrival times of sounds at the front ~o microphone Fmic and at the back microphone Bmic.
Preferably this delay is also adjustable and/or controllable.
Additionally, the output signal of the attenuator or controllable amplifier 1 is supplied to the positive 1s input of the combining circuit 5. In this combining circuit the delayed output signal of delay device 3 is subtracted from the attenuated output signal of amplifier or attenuator 1. The output signal of the combining circuit 5 is supplied as a processed signal 2o to the combining circuit 6. The output signal of the combining circuit 6 is then used as an input signal for further processing in the remaining components of the hearing aid such as the signal processor, which need not be described here.
2s The remaining parts of the hearing aid may, as known in the art, comprise more than one signal processing channel having either a common change-over controller or a separate controller for each channel.
As further known in the art, the output signals of 3o both microphones Fmic and Bmic may advantageously be converted into one or more digital representations before being supplied to the change-over controller with its components 1 to 6.
The function of the circuit in fig. 6 is as follows:
For the directional mode of operation, the signal transfer of the controllable attenuators 1 and 2 is set at s zero, i.e., no signal is transferred.
The output signal of the front microphone Fmic is directly supplied to the second adding circuit 6. The output signal of the back microphone Bmic is supplied via the first adding circuit 4 and the delay device 3 to 1o the negative input of the subtraction circuit 5, where the signal changes its polarity. The output signal of the subtraction circuit 5 is then supplied to a second input of the second adding circuit 6. Thus, the delayed signal from the back microphone Bmic is subtracted from the is undelayed output signal of the front microphone Fmic.
The directional front characteristic may then be created by adjusting the delay T of the delay device to be the same as the acoustical delay A between the back microphone Bmic and the front microphone F~nic. With this 2o delay, the signals that are first received at the back microphone Bmic and are later received at the front microphone Fmic are then suppressed in the adding circuit 6, where the delayed signal of the back microphone is subtracted from the output signal of the as front microphone.
This mode of operation provides an output signal from adding circuit 6 by subtraction of the delayed output signal of the back microphone Bmic from the output signal of the front microphone Fmic, thus substantially cancelling 3fl sound coming directly from the back of the user.
By adjusting T < A, sound coming partly from the side of the user is substantially cancelled, and the direction of the canceling effect is controlled by the ratio of T/A.
For the omnidirectional mode of operation, both s attenuators 1 and 2 are set for a full signal transfer.
The output signals from the front microphone Fmic and the back microphone Bmic are supplied to the first adding circuit 4, where they are combined and supplied via delay device 3 to the subtraction circuit 5. Then io the combined and delayed signal is subtracted from the output signal of the back microphone Bmic.
The output signal of the subtraction circuit 5 is then supplied to the second adding circuit 6, where it is combined with the undelayed output signal of the 15 front microphone Fmic. The addition of these signals creates the omnidirectional characteristic. This mode of operation provides an output signal from the adding circuit 6 by addition of the signals from the front and back microphones from which the delayed front and back 2o microphone signals are subtracted.
The arrival times of sound signals at the two microphones differ because the distances from the source to the two respective microphones differs.
This difference is the acoustical delay A, and the relationship between the sound signals Xfront and Xback received at the front and back microphones, respectively, may be generally expressed as * - j (D
Xback - Xfront a where e-i~ is the acoustical delay for the actual direc-tion to the sound source.
The combined signal Y from adding circuit 6 is 5 Y = Xfrcnc * ( 1 - omni * e-'~'T ) + Xback * ( omni - e-j'~'~ ) where omni is an adjustable parameter controlling attenuators 1 and 2, having a preferred value in the range from 0 to about 1 (i.e., the lower limit amni = 0 means no io signal transfers through attenuators 1 and 2, whereas the upper limit omni - 1 means maximum signal transfers through attenuators 1 and 2).
Although the invention is not limited thereto, the parameter omni should preferably be substantially the is same for both attenuators 1 and 2.
If the full directional mode of operation is chosen with omni = 0, then the combined signal Y becomes Y = X * (1-e-j~,cA.r~ ) front If the delay T is selected equal to the delay A
directly from the back microphone to the front microphone in the directional mode of operation, then the part of the sound signal X coming directly from the 2s back of the user is substantially suppressed and a directional characteristic known as a cardioid characteristic is provided.
The signal process described so far is preferably performed as a digital process in the time or frequency 3o domain. If processing in the frequency domain is employed, it is advantageous to use microphone circuits, which are capable of generating a delayed microphone output signal in combination with a non-delayed microphone output signal.
Figs. 7 to 10 are graphic representations of sound receiving characteristics and amplitude response of a hearing aid embodying the front end part shown in Fig. 6, corresponding to the representations in figs. 2 to 5 and using the same reference designations as in these figures.
As will appear from figs. 7 and 8, the part of the sound receiving characteristic representing the area in front of the user is substantially unaffected by the change over 1o between the omnidirectional characteristic ND and the various directional shapes D1 to D10. As illustrated by fig. 10, the amplitude response of signals received from the area in front of the user is substantially unaffected by the change over and remains substantially the same i r r a s p a c t i v a o f c h a n g a s t o coming from the area behind the user. Thereby, the adjustment or fitting of the hearing aid to compensate for the user's hearing impairment in quiet surroundings where the omnidirectional characteristic is used will also 2o provide improved listening performance when the hearing aid is used in a more noisy environment using a directional shape of the sound receiving characteristic.
The circuit in fig. 11 is similar to the circuit in fig. 6 and includes a change-over controller with components 1 to 6. Similar components have been assigned the same reference numerals.
Additionally, signal processing units 7 and 8 are placed at the outputs of the at least two microphones, e.g., the front microphone Fmic and the back microphone Bmic. The processed output signals of the two signal processing units 7 and 8 are then supplied to the change-over controller with components 1 to 6. The signal processing units 7 and 8 may perform an equalizing function on the two output signals of the two microphones, and/or may contain various filters (e. g., band pass filters). With the use of band pass filters, the microphone signals may be split up onto several bands, each equipped with its own change-over controller. The respective output signals from the adding circuits 6 in 1o the various bands or channels may then be combined into a composite combined signal to be further processed in the remaining stages of the hearing aid.
Fig. 12 shows a similar circuit diagram of the controller; for the same components the same reference numerals are used. In this circuit, the time delay for the output signals of the two microphones Fmic and Bmic is effected in separate delay units 3a and 3b representing the delay device 3. Otherwise, the function is similar to the function of the circuits of figs. 6 and 11. Furthermore, a control unit 9 is shown which may control the attenuation of the controllable attenuators 1 and 2 as well as the delays of delay units 3a and 3b.
This embodiment of the invention is useful in combination with microphone input circuits that are capable of supplying a delayed microphone signal together with an undelayed microphone signal for a hearing aid.
In the change-over controller the amplitude response as well as the time and phase of the audio signals are not changed when their directivity changes.
Fig. 13 schematically shows a further improvement of the front end circuit of a hearing aid including a s change-over controller as described so far with reference to fig. 6. Similar components have been _ designated with the same reference numerals as before.
Because of the technique used in combining the output signals of the two microphones Fmic and Bmic, the io resulting amplitude response of the output signals of the adding means 6 will in the relevant frequency range rise with 6 dB per octave compared to the amplitude response of a single microphone.
This behavior may be observed in substantially all is systems in which a delayed version of the output signal from the back microphone is subtracted from the undelayed output signal from the front microphone while achieving a directional effect.
However, in most cases, it is desirable to 2o compensate for this change in the amplitude response by adding a filter at the output of the front end of the hearing aid (i.e., at the adding circuit 6). Such a filter means a reduction of 6 dB per octave in the relevant frequency range, but also means that more circuit 2s components, time, and power would be required.
However, the change-over controller of the present invention can also be adapted to perform this compensation 3o filtering without the above-noted drawback. Therefore, there will be no need to add a filter at the output of the adding circuit 6.
For this purpose, an additional subtraction circuit is arranged between the adding circuit 4 and the i delay device 3, and the output signal of the adding circuit 6 is directly supplied to the negative input of adding means 10 in a feedback loop.
This new arrangement has the desired effect.
s It may be preferable to include in the feedback loop a controllable amplifier or attenuator 11.
Thus, the output signal of the change-over controller is fed back from the adding circuit 6 via the io controllable attenuator 11 to the negative input of subtraction circuit 10. Thus, the output signal of attenuator 11 is subtracted in the subtraction circuit from the output signal of adding circuit 4.
The resulting, output signal of subtraction circuit is 10 is supplied to the delay device 3 and hence to the negative input of the subtraction circuit 5, the positive input of which is connected to the output of the controllable attenuator 1.
In the schematic arrangements according to the 2o present invention in figs. 6 and 11 to 13, subtraction circuit 5 and adding circuit 6 can also be combined into a single combining circuit, provided this has, in every respect, the same properties as the two separate adding means 5 and 6.
25 Ideally, the gain factor of attenuator 11 should be one or unity for the filtering, being able to perform the 6 dB per octave fall at very low frequencies. However, this would probably result in a loop gain of unity so that the circuit might become unstable. Therefore, it is 3o preferred to have the gain of the amplifier or attenuator 11 set to a little less than one or unity.
In fig. 14 a further schematic arrangement of a hearing aid according to the present invention is shown.
The controllable attenuation and phase delay operations to .~
which the signals from the front and back microphones Fmic and Bmic are subjected before forming the overall combined signal are implemented by a different circuit structure as represented by the relationship stated in the s foregoing, i.e., X:ront * ( 1 - OIflIll * a j~) + Xback * ( 0!17111 - a 7t~~ ~ .
are implemented by a different circuit structure.
In this case, the change-over means comprises a first adding circuit 12 connected with the front and io back microphones Fmic and Bmic and a first~subtraction circuit 13 having a positive input connected with the front microphone Fmic and a negative input connected with the back microphone Bmic. First and second phase delay devices 14 and 15 are connected with the first is subtraction and adding circuits 13 and 12, respectively.
A second adding circuit 16 is connected with the first subtraction circuit 13 and the first phase delay device l4,and a second subtracting circuit 17 has its positive input connected with the first adding circuit 12 and its 2o negative input connected with second phase delay device 15. A first controllable attenuator 18 acts on the signal from the second adding circuit 16 for attenuation of this signal by a factor (1 - omni)/2, and a second controllable attenuator 19 acts on the signal from the 2s second subtraction circuit 17 for attenuation of this signal by a factor (1 + omni)/2, whereas a third adding circuit 20 is connected with the first and second attenuators 18 and 19 for addition of the signals therefrom to provide the overall combined signal to be 3o supplied to the signal processor.
The microphones used in the description above are preferably omnidirectional microphones.
AW' when two microphones are used in the omni-directional mode of operation, both microphones generate an electrical noise signal N. These two noise signals have a similar power:
C Nback ( ' ~ Nfront ~ ~
where Nback is the noise signal from the back microphone Bmic, and Nfront is the noise signal from the front to microphone Fmic.
The noise signals N are random signals. Therefore, the resulting signal amplitude is less than twice the single amplitude. Thus, a 3 dB-noise reduction results.
The total noise signal can be calculated as:
INIz-INfrontl2*,1'OI11I11*e jmT~z+INpacklZ*I1-OIflIll*e ~~TI2 ~N~°~N:ro,t~*2°.s11_omn.i*e~~''~) 2o It has been shown that with the new front end of a hearing aid comprising a change-over controller in accordance with the invention a great variety of directional characteristics patterns may be controllably realized.
The present invention describes a method for controlling the directionality of the sound receiving characteristic of a hearing aid, comprising spaced apart first and second sound receiving microphone means, a signal processor for processing signals supplied by said microphone means and an output transducer for emission of sound signals in response to output signals from the signal processor, said method comprising the steps of 2o changing over said sound receiving characteristic between an omnidirectional characteristic and a directional characteristic and, while operating the hearing aid with said directional characteristic, combining the signals supplied by said first and second microphone means into an overall combined signal, an adjustable time or phase delay being imposed on at least one signal, wherein said change over of the sound receiving characteristic from the omnidirectional characteristic to the directional characteristic and vice versa is effected by controlling 3o the attenuation and the time or phase delay of signals derived from both of the signals (Xfront~ Xback) from the first and second microphone means before forming said overall combined signal (Y), according to an adjustable attenuation control parameter (omni) and a delay (T), 5 whereby said overall combined signal (Y) is determined by Y ° Xfro~t * (1 - omni * e''"T) ~' Xback * (omni - e''"T) , to change over the hearing aid between said omnidirectional characteristic and any desired form of said directional characteristic as a smooth change over substantially 1o without effecting phase relationship, time delay and amplitude characteristic of the hearing aid.
The present invention also describes a hearing aid with controllable directionality of its sound receiving characteristic, comprising spaced apart first and second sound receiving microphones means, a signal processor for processing signals supplied by said microphone means and an output transducer for emission of sound signals in response to output signals from the signal processor, and further comprising change-over 2o control means for change over of the sound receiving characteristic between an omnidirectional characteristic and a directional characteristic and combining means for combining of the signals from the first and second microphone means to provide an overall combined signal supplied to the signal processor, while operating the hearing aid with said directional characteristic, and adjustable time or phase delay means for producing a phase-delayed modification of at least one signal, wherein said change-over control means comprises 3o controllable attenuation means and controllable time or phase delay means acting on signals derived from the signals (Xf=ont~ Xback) from both of the first and second microphone means, respectively, said attenuation and phase delay means (1-3; 14, 15, 18, 19) being controlled for forming said overall combined signal (Y) according to an adjustable attenuation control parameter (omni) and a delay (T), whereby said overall combined signal (Y) is determined by Y = Xf=ont * (1 - omni * e'~"T) + Xback * (omni - e''"'') , to change over the hearing aid between said omnidirectional characteristic and any desired form of said directional characteristic as a smooth change over substantially without affecting phase relationship, time delay and amplitude characteristic of the hearing aid.
In an aspect of the present invention, there is provided a directional controller for a hearing aid for processing input signals from at least two spaced apart microphones for producing a combined output signal for further processing in the hearing aid, the directional controller comprising adjustable time delay means for 2o producing a time-delayed modification of at least one signal, and change-over control means for effecting a change-over between an omnidirectional mode and a directional mode, and further comprising a first controllable attenuator for processing a signal derived from the signal (Xpront) from the first microphone to output a first processed signal, a second controllable attenuator for processing a signal derived from the signal (Xback) from the second microphone to output a second processed signal, the adjustable time delay 3o means being adapted for delaying signals derived from the signals from both of the first and the second microphones and combining means connected to combine the processed and delayed signals with the output signal from the first microphone to generate the combined output signal, the change-over control means being connected to control the controllable attenuator.
In the following the invention will be further explained with reference to the accompanying illustrative example drawings, in which Fig. 1 is a schematic block diagram of the prior art hearing aid of United States Patent No. 5,757,933, Figs. 2 to 5 are graphic representations illustrating variations of the sound receiving characteristic of the hearing aid in fig. 1 between the omnidirectional characteristic and different directional shapes and concurrent variation of amplitude characteristics of the front and back microphones used therein, Fig. 6 shows a schematic arrangement of the front end of a hearing aid according to the present invention, Figs. 7 to 10 are graphic representations corresponding to the representations in figs.2 to 5 with respect to the hearing aid shown in Fig. 6, Fig. 11 shows a schematic arrangement of a hearing aid according to the present invention with a change-over controller, Fig. 12 shows a similar schematic arrangement of an embodiment of the present invention, Fig. 13 schematically shows a schematic arrangement providing a further improvement of the arrangement shown 3o in Fig. 6, and Fig. 14 shows a schematic arrangement providing a further development of a hearing aid according to the invention.
s In the prior art hearing aid . shown in Fig. 1, two non-directional microphone circuits include a front microphone MICF and a back microphone MICB. Whereas the output signal from the front microphone MICF is supplied directly to the hearing aid signal processor via a summing node SN, the signal from the back microphone is supplied to the summing node SN (i.e., via an inverter, an adjustable phase delay circuit, and an attenuator with adjustable gain) only by closure of a manually operated 1o switch SW, whereby the sound receiving characteristic of the hearing is changed from the omnidirectional characteristic of front microphone MICF to a directional characteristic of varying shape.
The combined signal Y formed at the summing node SN
1s with switch SW closed and supplied to the signal processor will thus be related to the signals Xfront and Xback from front and back microphones MICF and MICE, respectively, by the relation Y = Xfront " Xback * omni * e' j~''. Here, the adjustable parameter omni represents the 2o adjustable gain of the attenuator, whereas T represents the adjustable time delay corresponding to the difference in arrival time for sound signals received by the front and back microphones MICF and MICB, respectively.
The graphic representations in figs. 2 25 and 3 illustrate examples of the variation of the sound receiving characteristic of the hearing aid in figure 1 from the omnidirectional shape ND and various directional shapes D1 to D10, ranging from weak cardioid to super cardioid form for values of the adjustable 3o parameter omni ranging from 0 to 1, measured at lkHz and 100 Hz, respectively. The graphic representations in figs. 4 and 5 show the variation in the amplitude characteristics of the signals received from the areas in front and back of the hearing aid, respectively, for correspondingly varying values of the parameter omni. As will appear from these representations for this prior art hearing aid, the change-over between the omnidirectional characteristic and the various shapes of directional characteristic results in the desired gradual reduction in 1o gain or amplitude response for the signals received from the area behind the user. However, this is also accompanied by a significant change in gain or amplitude response for the signals received from the area in front of the user. Consequently, adjustment or fitting of the hearing aid to compensate for a user's specific hearing impairment in quiet surroundings (i.e., where use of the omnidirectional characteristic is preferred) will not provide optimum compensation when a change-over is made to a directional characteristic, (i.e., where use of the 2p hearing aid in a more noisy sound environment, such as a party, is preferred).
Fig. 6, shows the front end of a hearing aid, including a change-over controller for controlling change of the directionality of sound receiving characteristic of the hearing aid from the omnidirectional characteristic to a directional charac-1~
teristic, and vice versa. This change may be effected as a switch-over, or as a gradual and smooth change-over.
The front end of the hearing aid comprises at least two microphone circuits (e.g., a front microphone Fmic and s a back microphone Bmic) and possibly optional preprocessing circuits for the electrical output signals from the microphones. The distance between the two microphones may be as small as about 1 man or as wide as about a few cm.
1o The front end further contains at~ least two controllable amplifiers or attenuators l and 2, at least one time or phase delay device 3, and at least three combining circuits 4, 5, and 6. It is to be understood that the combining circuits may contain positive as well is as negative input terminals, so as to form adding or subtraction operations or combinations thereof.
In the structure, the back microphone Bmic is connected to the controllable amplifier or attenuator 1 and to a first adding circuit 4.
2o The front microphone Fmic is connected directly to the controllable amplifier or attenuator 2 and to a second adding circuit 6. The output of the controllable amplifier or attenuator 2 is further connected directly to a second input of the first adding circuit 4, whereas 2s the output of the controllable amplifier 1 is directly connected to a positive input of a subtraction circuit 5.
Preferably, a controllable delay device 3 is included between the output of the first adding circuit 4 and the 3o negative input of the subtraction circuit 5.
In the following description the adding and subtracting circuits will generally be referred to as combining circuits.
In operation, sound from the environment of the hearing aid is picked up by both the front microphone Gmic and the back microphone Bmic. The distance between the two microphones may be as small as about 1 mm and as s wide as about a few cm.
The output signal of the front microphone F~nic is supplied to the combining circuit 6. The output signal of the back microphone Bmic is supplied to the controllable attenuator or controllable amplifier 1, and the gain can io be controllably changed from zero to about one, i.e., from no amplification to substantially full amplification.
This change-over may be effected as a switch-over or as a controlled gradual change. This means that amplification between zero and about one can be controllably achieved.
i5 Any output signal from the front microphone EYnic is also supplied to a controllable attenuator or amplifier 2, and the amplification may controllably be changed from zero to about one, i.e., from no amplification to substantially full amplification. Also in this case, the 2o change-over may be effected as a switch-over or as a gradual controlled change. This means that amplification between zero and about one may be achieved.
Any output signal from the controllable attenuator or amplifier 2 is supplied to a second input of the combining 2s circuit 4. Any output signal of combining circuit 4 is supplied to the controllable delay device 3, and the delay may be controlled from as small as about 1 us up to about 1000 us or more.
Any output signal of delay device 3 is supplied to 3o the negative input of combining circuit 5, and the output is supplied to the second input of the combining circuit 6.
Thereby, the output signal of the front microphone F~nic rnay be attenuated in the attenuator or controllable amplifier 2 before it is added to the undelayed output signal of the back microphone Bmic in the combining s circuit 4, the output signal of which is then delayed in delay device 3 before being supplied to the combining circuit 5. The controllable delay of delay device 3 will usually have the same value as the acoustical delay between the arrival times of sounds at the front ~o microphone Fmic and at the back microphone Bmic.
Preferably this delay is also adjustable and/or controllable.
Additionally, the output signal of the attenuator or controllable amplifier 1 is supplied to the positive 1s input of the combining circuit 5. In this combining circuit the delayed output signal of delay device 3 is subtracted from the attenuated output signal of amplifier or attenuator 1. The output signal of the combining circuit 5 is supplied as a processed signal 2o to the combining circuit 6. The output signal of the combining circuit 6 is then used as an input signal for further processing in the remaining components of the hearing aid such as the signal processor, which need not be described here.
2s The remaining parts of the hearing aid may, as known in the art, comprise more than one signal processing channel having either a common change-over controller or a separate controller for each channel.
As further known in the art, the output signals of 3o both microphones Fmic and Bmic may advantageously be converted into one or more digital representations before being supplied to the change-over controller with its components 1 to 6.
The function of the circuit in fig. 6 is as follows:
For the directional mode of operation, the signal transfer of the controllable attenuators 1 and 2 is set at s zero, i.e., no signal is transferred.
The output signal of the front microphone Fmic is directly supplied to the second adding circuit 6. The output signal of the back microphone Bmic is supplied via the first adding circuit 4 and the delay device 3 to 1o the negative input of the subtraction circuit 5, where the signal changes its polarity. The output signal of the subtraction circuit 5 is then supplied to a second input of the second adding circuit 6. Thus, the delayed signal from the back microphone Bmic is subtracted from the is undelayed output signal of the front microphone Fmic.
The directional front characteristic may then be created by adjusting the delay T of the delay device to be the same as the acoustical delay A between the back microphone Bmic and the front microphone F~nic. With this 2o delay, the signals that are first received at the back microphone Bmic and are later received at the front microphone Fmic are then suppressed in the adding circuit 6, where the delayed signal of the back microphone is subtracted from the output signal of the as front microphone.
This mode of operation provides an output signal from adding circuit 6 by subtraction of the delayed output signal of the back microphone Bmic from the output signal of the front microphone Fmic, thus substantially cancelling 3fl sound coming directly from the back of the user.
By adjusting T < A, sound coming partly from the side of the user is substantially cancelled, and the direction of the canceling effect is controlled by the ratio of T/A.
For the omnidirectional mode of operation, both s attenuators 1 and 2 are set for a full signal transfer.
The output signals from the front microphone Fmic and the back microphone Bmic are supplied to the first adding circuit 4, where they are combined and supplied via delay device 3 to the subtraction circuit 5. Then io the combined and delayed signal is subtracted from the output signal of the back microphone Bmic.
The output signal of the subtraction circuit 5 is then supplied to the second adding circuit 6, where it is combined with the undelayed output signal of the 15 front microphone Fmic. The addition of these signals creates the omnidirectional characteristic. This mode of operation provides an output signal from the adding circuit 6 by addition of the signals from the front and back microphones from which the delayed front and back 2o microphone signals are subtracted.
The arrival times of sound signals at the two microphones differ because the distances from the source to the two respective microphones differs.
This difference is the acoustical delay A, and the relationship between the sound signals Xfront and Xback received at the front and back microphones, respectively, may be generally expressed as * - j (D
Xback - Xfront a where e-i~ is the acoustical delay for the actual direc-tion to the sound source.
The combined signal Y from adding circuit 6 is 5 Y = Xfrcnc * ( 1 - omni * e-'~'T ) + Xback * ( omni - e-j'~'~ ) where omni is an adjustable parameter controlling attenuators 1 and 2, having a preferred value in the range from 0 to about 1 (i.e., the lower limit amni = 0 means no io signal transfers through attenuators 1 and 2, whereas the upper limit omni - 1 means maximum signal transfers through attenuators 1 and 2).
Although the invention is not limited thereto, the parameter omni should preferably be substantially the is same for both attenuators 1 and 2.
If the full directional mode of operation is chosen with omni = 0, then the combined signal Y becomes Y = X * (1-e-j~,cA.r~ ) front If the delay T is selected equal to the delay A
directly from the back microphone to the front microphone in the directional mode of operation, then the part of the sound signal X coming directly from the 2s back of the user is substantially suppressed and a directional characteristic known as a cardioid characteristic is provided.
The signal process described so far is preferably performed as a digital process in the time or frequency 3o domain. If processing in the frequency domain is employed, it is advantageous to use microphone circuits, which are capable of generating a delayed microphone output signal in combination with a non-delayed microphone output signal.
Figs. 7 to 10 are graphic representations of sound receiving characteristics and amplitude response of a hearing aid embodying the front end part shown in Fig. 6, corresponding to the representations in figs. 2 to 5 and using the same reference designations as in these figures.
As will appear from figs. 7 and 8, the part of the sound receiving characteristic representing the area in front of the user is substantially unaffected by the change over 1o between the omnidirectional characteristic ND and the various directional shapes D1 to D10. As illustrated by fig. 10, the amplitude response of signals received from the area in front of the user is substantially unaffected by the change over and remains substantially the same i r r a s p a c t i v a o f c h a n g a s t o coming from the area behind the user. Thereby, the adjustment or fitting of the hearing aid to compensate for the user's hearing impairment in quiet surroundings where the omnidirectional characteristic is used will also 2o provide improved listening performance when the hearing aid is used in a more noisy environment using a directional shape of the sound receiving characteristic.
The circuit in fig. 11 is similar to the circuit in fig. 6 and includes a change-over controller with components 1 to 6. Similar components have been assigned the same reference numerals.
Additionally, signal processing units 7 and 8 are placed at the outputs of the at least two microphones, e.g., the front microphone Fmic and the back microphone Bmic. The processed output signals of the two signal processing units 7 and 8 are then supplied to the change-over controller with components 1 to 6. The signal processing units 7 and 8 may perform an equalizing function on the two output signals of the two microphones, and/or may contain various filters (e. g., band pass filters). With the use of band pass filters, the microphone signals may be split up onto several bands, each equipped with its own change-over controller. The respective output signals from the adding circuits 6 in 1o the various bands or channels may then be combined into a composite combined signal to be further processed in the remaining stages of the hearing aid.
Fig. 12 shows a similar circuit diagram of the controller; for the same components the same reference numerals are used. In this circuit, the time delay for the output signals of the two microphones Fmic and Bmic is effected in separate delay units 3a and 3b representing the delay device 3. Otherwise, the function is similar to the function of the circuits of figs. 6 and 11. Furthermore, a control unit 9 is shown which may control the attenuation of the controllable attenuators 1 and 2 as well as the delays of delay units 3a and 3b.
This embodiment of the invention is useful in combination with microphone input circuits that are capable of supplying a delayed microphone signal together with an undelayed microphone signal for a hearing aid.
In the change-over controller the amplitude response as well as the time and phase of the audio signals are not changed when their directivity changes.
Fig. 13 schematically shows a further improvement of the front end circuit of a hearing aid including a s change-over controller as described so far with reference to fig. 6. Similar components have been _ designated with the same reference numerals as before.
Because of the technique used in combining the output signals of the two microphones Fmic and Bmic, the io resulting amplitude response of the output signals of the adding means 6 will in the relevant frequency range rise with 6 dB per octave compared to the amplitude response of a single microphone.
This behavior may be observed in substantially all is systems in which a delayed version of the output signal from the back microphone is subtracted from the undelayed output signal from the front microphone while achieving a directional effect.
However, in most cases, it is desirable to 2o compensate for this change in the amplitude response by adding a filter at the output of the front end of the hearing aid (i.e., at the adding circuit 6). Such a filter means a reduction of 6 dB per octave in the relevant frequency range, but also means that more circuit 2s components, time, and power would be required.
However, the change-over controller of the present invention can also be adapted to perform this compensation 3o filtering without the above-noted drawback. Therefore, there will be no need to add a filter at the output of the adding circuit 6.
For this purpose, an additional subtraction circuit is arranged between the adding circuit 4 and the i delay device 3, and the output signal of the adding circuit 6 is directly supplied to the negative input of adding means 10 in a feedback loop.
This new arrangement has the desired effect.
s It may be preferable to include in the feedback loop a controllable amplifier or attenuator 11.
Thus, the output signal of the change-over controller is fed back from the adding circuit 6 via the io controllable attenuator 11 to the negative input of subtraction circuit 10. Thus, the output signal of attenuator 11 is subtracted in the subtraction circuit from the output signal of adding circuit 4.
The resulting, output signal of subtraction circuit is 10 is supplied to the delay device 3 and hence to the negative input of the subtraction circuit 5, the positive input of which is connected to the output of the controllable attenuator 1.
In the schematic arrangements according to the 2o present invention in figs. 6 and 11 to 13, subtraction circuit 5 and adding circuit 6 can also be combined into a single combining circuit, provided this has, in every respect, the same properties as the two separate adding means 5 and 6.
25 Ideally, the gain factor of attenuator 11 should be one or unity for the filtering, being able to perform the 6 dB per octave fall at very low frequencies. However, this would probably result in a loop gain of unity so that the circuit might become unstable. Therefore, it is 3o preferred to have the gain of the amplifier or attenuator 11 set to a little less than one or unity.
In fig. 14 a further schematic arrangement of a hearing aid according to the present invention is shown.
The controllable attenuation and phase delay operations to .~
which the signals from the front and back microphones Fmic and Bmic are subjected before forming the overall combined signal are implemented by a different circuit structure as represented by the relationship stated in the s foregoing, i.e., X:ront * ( 1 - OIflIll * a j~) + Xback * ( 0!17111 - a 7t~~ ~ .
are implemented by a different circuit structure.
In this case, the change-over means comprises a first adding circuit 12 connected with the front and io back microphones Fmic and Bmic and a first~subtraction circuit 13 having a positive input connected with the front microphone Fmic and a negative input connected with the back microphone Bmic. First and second phase delay devices 14 and 15 are connected with the first is subtraction and adding circuits 13 and 12, respectively.
A second adding circuit 16 is connected with the first subtraction circuit 13 and the first phase delay device l4,and a second subtracting circuit 17 has its positive input connected with the first adding circuit 12 and its 2o negative input connected with second phase delay device 15. A first controllable attenuator 18 acts on the signal from the second adding circuit 16 for attenuation of this signal by a factor (1 - omni)/2, and a second controllable attenuator 19 acts on the signal from the 2s second subtraction circuit 17 for attenuation of this signal by a factor (1 + omni)/2, whereas a third adding circuit 20 is connected with the first and second attenuators 18 and 19 for addition of the signals therefrom to provide the overall combined signal to be 3o supplied to the signal processor.
The microphones used in the description above are preferably omnidirectional microphones.
AW' when two microphones are used in the omni-directional mode of operation, both microphones generate an electrical noise signal N. These two noise signals have a similar power:
C Nback ( ' ~ Nfront ~ ~
where Nback is the noise signal from the back microphone Bmic, and Nfront is the noise signal from the front to microphone Fmic.
The noise signals N are random signals. Therefore, the resulting signal amplitude is less than twice the single amplitude. Thus, a 3 dB-noise reduction results.
The total noise signal can be calculated as:
INIz-INfrontl2*,1'OI11I11*e jmT~z+INpacklZ*I1-OIflIll*e ~~TI2 ~N~°~N:ro,t~*2°.s11_omn.i*e~~''~) 2o It has been shown that with the new front end of a hearing aid comprising a change-over controller in accordance with the invention a great variety of directional characteristics patterns may be controllably realized.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A directional controller for a hearing aid for processing input signals from at least two spaced apart microphones for producing a combined output signal for further processing in the hearing aid, the directional controller comprising adjustable time delay means for producing a time-delayed modification of at least one signal, and change-over control means for effecting a change-over between an omnidirectional mode and a directional mode, and further comprising a first controllable attenuator for processing a signal derived from the signal (X front) from the first microphone to output a first processed signal, a second controllable attenuator for processing a signal derived from the signal (X back) from the second microphone to output a second processed signal, said adjustable time delay means being adapted for delaying signals derived from the signals from both of the first and the second microphones and combining means connected to combine the processed and delayed signals with the output signal from the first microphone to generate the combined output signal, said change-over control means being connected to control the controllable attenuator.
2. A directional controller in accordance with claim 1, wherein the first controllable attenuator further comprises a controllable amplifier.
3. A directional controller in accordance with claim 1 or 2, wherein the second controllable attenuator further comprises a controllable amplifier.
4. A directional controller in accordance with anyone of claims 1 to 3, further comprising a control unit for controlling the controllable attenuator.
5. A directional controller in accordance with claim 4, wherein the control unit is adapted for controlling the delay of the delay means.
6. A directional controller in accordance with any one of claims 1 to 5, wherein the combining means comprises a first adding means connected to combine the output signal from the first controllable attenuator with the output signal from the second microphone to output a signal for processing in the delay means for the generation of a combined processed signal, which combined processed signal is supplied to a second adding means for combination with the second processed signal.
7. A directional controller in accordance with claim 6, further comprising a fourth adding means arranged in front of the delay device and connected via a feed-back loop to subtract the combined output signal from the signal outputted from the first adding means.
8. A directional controller in accordance with claim 7, further comprising a controllable amplifier arranged to process the output signal fed to the fourth adding means.
9. A directional controller in accordance with claim 8, wherein the controllable amplifier is adapted to provide a gain, which is somewhat less than unity.
10. A directional controller in accordance with any one of claims 1 to 5, wherein the delay means comprises separate first and second delay units for receiving output signals from the first and second microphones, respectively, the first delay device supplying a delayed output signal to the first controllable attenuator, a first adding means being connected to receive the first processed signal along with the output signal from the second delay unit at respective negative inputs and, at a positive input, the second processed signal.
11. A directional controller in accordance with any one of claims 1 to 5, wherein the change-over means comprises a first adding circuit connected with the first and the second microphones, a first subtraction circuit having a positive input connected with the first microphone and a negative input connected with the second microphone, a first delay device connected with the output of the first subtraction circuit, a second delay device connected with the output of the first adding circuit, a second adding circuit connected with the first subtraction circuit and the first delay device, a second subtraction circuit having its positive input connected with the first adding circuit and its negative input connected with second delay device, a first controllable attenuator acting on the signal from the second adding circuit for attenuating this signal by a factor (1 -omni)/2 and a second controllable attenuator acting on the signal from the second subtraction circuit for attenuating this signal by a factor (1 + omni)/2, and a third adding circuit connected with the first and second attenuators for adding the signals therefrom to provide the combined output signal.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/EP1999/004375 WO2001001732A1 (en) | 1999-06-24 | 1999-06-24 | Hearing aid with controllable directional characteristics |
| EPPCT/EP99/04375 | 1999-06-24 | ||
| CA002385812A CA2385812C (en) | 1999-06-24 | 2000-06-23 | A method for controlling the directionality of the sound receiving characteristic of a hearing aid and a hearing aid for carrying out the method |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002385812A Division CA2385812C (en) | 1999-06-24 | 2000-06-23 | A method for controlling the directionality of the sound receiving characteristic of a hearing aid and a hearing aid for carrying out the method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2479675A1 CA2479675A1 (en) | 2001-01-04 |
| CA2479675C true CA2479675C (en) | 2006-06-06 |
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| CA002385812A Expired - Fee Related CA2385812C (en) | 1999-06-24 | 2000-06-23 | A method for controlling the directionality of the sound receiving characteristic of a hearing aid and a hearing aid for carrying out the method |
| CA002479675A Expired - Fee Related CA2479675C (en) | 1999-06-24 | 2000-06-23 | Directional controller for a hearing aid |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002385812A Expired - Fee Related CA2385812C (en) | 1999-06-24 | 2000-06-23 | A method for controlling the directionality of the sound receiving characteristic of a hearing aid and a hearing aid for carrying out the method |
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| JP (1) | JP3914768B2 (en) |
| AT (1) | ATE248496T1 (en) |
| AU (2) | AU4776999A (en) |
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| DE (1) | DE60004863T2 (en) |
| DK (1) | DK1203508T3 (en) |
| WO (2) | WO2001001732A1 (en) |
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| DE10310579B4 (en) | 2003-03-11 | 2005-06-16 | Siemens Audiologische Technik Gmbh | Automatic microphone adjustment for a directional microphone system with at least three microphones |
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| EP1665881B1 (en) * | 2003-09-19 | 2008-07-23 | Widex A/S | A method for controlling the directionality of the sound receiving characteristic of a hearing aid and a signal processing apparatus for a hearing aid with a controllable directional characteristic |
| KR20040028889A (en) * | 2004-02-24 | 2004-04-03 | 장순석 | One Side ITE(In-The-Ear) Hearing Aid with Opposite Side Directivity Increment |
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| DE102004052912A1 (en) | 2004-11-02 | 2006-05-11 | Siemens Audiologische Technik Gmbh | Method for reducing interference power in a directional microphone and corresponding acoustic system |
| DK1949755T3 (en) | 2005-10-11 | 2010-08-23 | Widex As | Hearing aid and method of processing input signals in a hearing aid |
| EP1941782B1 (en) | 2005-10-18 | 2018-07-18 | Widex A/S | Equipment for programming a hearing aid and a hearing aid |
| EP2243303A1 (en) * | 2008-02-20 | 2010-10-27 | Koninklijke Philips Electronics N.V. | Audio device and method of operation therefor |
| JP4649546B2 (en) | 2009-02-09 | 2011-03-09 | パナソニック株式会社 | hearing aid |
| DE102010011730A1 (en) | 2010-03-17 | 2011-11-17 | Siemens Medical Instruments Pte. Ltd. | Hearing apparatus and method for generating an omnidirectional directional characteristic |
| US9668065B2 (en) | 2015-09-18 | 2017-05-30 | Sonion Nederland B.V. | Acoustical module with acoustical filter |
| DK3148218T3 (en) * | 2015-09-18 | 2020-02-24 | Sonion Nederland Bv | ACOUSTIC MODULE WITH ACOUSTIC FILTER |
| DK179577B1 (en) | 2016-10-10 | 2019-02-20 | Widex A/S | Binaural hearing aid system and a method of operating a binaural hearing aid system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DK159357C (en) * | 1988-03-18 | 1991-03-04 | Oticon As | HEARING EQUIPMENT, NECESSARY FOR EQUIPMENT |
| US5128566A (en) * | 1989-11-03 | 1992-07-07 | Etymotic Research, Inc. | Variable attenuator circuit |
| AT407815B (en) * | 1990-07-13 | 2001-06-25 | Viennatone Gmbh | HEARING AID |
| CH681188A5 (en) * | 1990-10-30 | 1993-01-29 | Ascom Audiosys Ag | |
| US5524056A (en) * | 1993-04-13 | 1996-06-04 | Etymotic Research, Inc. | Hearing aid having plural microphones and a microphone switching system |
| US5757933A (en) * | 1996-12-11 | 1998-05-26 | Micro Ear Technology, Inc. | In-the-ear hearing aid with directional microphone system |
-
1999
- 1999-06-24 WO PCT/EP1999/004375 patent/WO2001001732A1/en active Application Filing
- 1999-06-24 AU AU47769/99A patent/AU4776999A/en not_active Abandoned
-
2000
- 2000-06-23 JP JP2001506270A patent/JP3914768B2/en not_active Expired - Fee Related
- 2000-06-23 WO PCT/DK2000/000339 patent/WO2001001731A1/en active IP Right Grant
- 2000-06-23 AU AU53916/00A patent/AU766876B2/en not_active Ceased
- 2000-06-23 CA CA002385812A patent/CA2385812C/en not_active Expired - Fee Related
- 2000-06-23 CA CA002479675A patent/CA2479675C/en not_active Expired - Fee Related
- 2000-06-23 DE DE60004863T patent/DE60004863T2/en not_active Expired - Lifetime
- 2000-06-23 AT AT00938590T patent/ATE248496T1/en not_active IP Right Cessation
- 2000-06-23 DK DK00938590T patent/DK1203508T3/en active
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|---|---|
| ATE248496T1 (en) | 2003-09-15 |
| DE60004863D1 (en) | 2003-10-02 |
| CA2479675A1 (en) | 2001-01-04 |
| JP3914768B2 (en) | 2007-05-16 |
| WO2001001731A1 (en) | 2001-01-04 |
| WO2001001732A1 (en) | 2001-01-04 |
| DK1203508T3 (en) | 2003-09-22 |
| DE60004863T2 (en) | 2004-05-06 |
| CA2385812C (en) | 2005-06-07 |
| AU4776999A (en) | 2001-01-31 |
| CA2385812A1 (en) | 2001-01-04 |
| AU766876B2 (en) | 2003-10-23 |
| JP2003503924A (en) | 2003-01-28 |
| AU5391600A (en) | 2001-01-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20170623 |