AU749652B2 - Method for electronically selecting the dependency of an output signal from the spatial angle of acoustic signal impingement and hearing aid apparatus - Google Patents

Abstract

For beam forming acoustical signals the phase difference of the output signals of two acoustical/electrical transducers is determined (27) and is multiplied by a factor (30). One of the two output signals of the at least two transducers is phase shifted by an amount according to the multiplication result. This phase shifted signal and the signal of the second transducer are led to a signal processing unit, wherein beam forming on these at least two signals is performed. Thereby, it becomes possible to perform beam forming as if the transducers were mutually distant by more than they physically are. <IMAGE>

Description

WO 99/04598 PCT/IB98/01069 -1- Method for electronically selecting the dependency of an output signal from the spatial angle of acoustic signal impingement and hearing aid apparatus The present invention is generically directed on a technique according to which acoustical signals are received by at least two acoustical/electrical converters as e.g. by multidirectional microphones, respective output signals of such converters are electronically computed by an electronic transducer unit so as to generate an output signal which represents the acoustical signals weighted by a spatial characteristic of amplification. Thus, the output signal represents thereceived acoustical signal weighted by the spatial amplification characteristic as if reception of the acoustical signals had been done by means of e.g. an antenna with an according reception lobe or beam. Thus, the present invention is generically directed on an electronically preset, possibly electronically adjusted and tailored reception "lobe".

Figure 1 most generically shows such known technique for such "beam forming" on acoustical signals. Thereby, at least two multidirectional acoustical/electrical converters 2a and 2 b are provided, which both per se convert acoustical signal irrespective of their impinging direction 8 and thus substantially unweighted with respect to impinging direction 8 into first and second electrical output signals Al and A 2 The output signals Al and A 2 are fed to an electronic transducer unit 3 which generates from the input signals Al, A 2 an output signal As shown within the block of unit 3 the signals A, 12 are treated to result in the result signal A, which represents either of A. or A2, but additionally weighted by the spatial amplification function F 1 Thus, acoustic signals may selectively be am- CONFIRMATION COPY WO 99/04598 PCT/IB98/01069 2 plified dependent from the fact under which spatial angle 0 they impinge, i.e. under which spatial angle the transducer arrangement 2a, 2b "sees" an acoustical source. Thereby, such known approach is strictly bound to the physical- location and intrinsic "lobe" of the converters as provided.

One approach to perform signal processing within transducer unit 3 shall be exemplified with the help of Fig. 2. Thereby, all such approaches are based on the fact that due to a predetermined mutual physical distance p, of the two converters 2a and 2 b, there occurs a time-lag dt between reception of an acoustical signal at the converters 2 a, 2 b' Considering a single frequency o acoustical signal, received by the converter this converter will generate an output signal AI A* sinot, whereas the second transducer 2 b will generate an output signal according to A, A sino(t+dt), whereat dt is given by PpsinO dt p ps -c therein, c is the sound velocity.

By time-delaying e.g. A, by an amount pp/c BSS^8S11 N fi2MISS3S'Pt g155"MAW WO 99/04598 PCT/IB98/01069 3 and forming the result signal A, from the difference of timedelayed signal as a third signal namely from AI' A sin and

A

2 A sino(t+dt), there results, considered at the frequency o, a spatially cardoid weighted output signal A, as shown in the block of transducer unit 3: IlA IA,' A 2 2A sin(co(T-dt)/2) 2A sin(co(T-pp*sinO/c)/2) At 0 900 Ar becomes zero and at 8 -900 A, becomes Aa 2A sin o p,/c.

Such processing of the output signals of two omnidirectional order converters leads to a first order cardoid weighing function as shown in Fig. 3. By respectively selecting converters with higher order acoustical to electrical conversion characteristic i.e. "lobe" and/or by using more than two converters, higher order m weighing functions may be realised.

In Fig. 4 there is shown the amplitude A,-characteristic, resulting from first order cardoid weighing as a function of frequency f o/2T. Additionally, the respective function for a second order cardoid weighing function is shown. Thereby, there is selected a physical distance pp of the two converters 2a and 2 b of fig. 1 to be 12 mm.

WO 99/04598 PCT/IB98/01069 4 As may clearly be seen at a frequency f, which is c/(4pp) maximum amplification occurs of +6 dB at the first order cardoid and of +12 dB at a second order cardoid. For p, 12 mm, fr is about 7 kHz.

From fig. 4 a significant roll-off for low and high frequencies with respect to f, is recognised, i.e. a significant decrease of amplification.

Techniques for such or similar type of beam forming are e.g.

known from the US 4 333 170 acoustical source detection from the European patent application 0 381 498 directional microphone or from Norio Koike et al., "Verification of the Possibility of Separation of Sound Source Direction via a Pair of Pressure Microphones", Electronics and Communications in Japan, Part 3, Vol. 77, No. 5, 1994, page 68 to Irrespective of the prior art techniques used for such beam forming with at least two converters, the distance p, is an important entity as may be seen e.g. from formula and directly determines the resulting amplification/angle dependency.

Formula may be of no special handicap if such a technique is used for narrow band signal detection or if no serious limits are encountered for geometrically providing the at least two converters at a large mutual physical distance p,.

Nevertheless, and especially for hearing aid applications, the fact that f, is inversely proportional to the physical distance pp of the transducers is a serious drawback, due to the fact that for hearing aid applications the audio frequency band up ~7 7 WO 99/04598 PCTIB98/01069 to about 4 kHz for speech recognition should be detectable by the at least two transducers which further should be mounted with the shortest possible mutual distance pp. These two requirements are in contradiction: The lower f, shall be realised, the larger will be the distance pp required.

It is thus a first object of the present invention to remedy the drawbacks encountered with respect to p,-dependency of known acoustical "beam forming" The first object of the present invention is reached by providing a method for electronically selecting the dependency of an electric output signal of an electronic transducer unit from spatial direction wherefrom acoustical signals impinge on at least a first and a second acoustical/electrical converter, connected to the inputs of said transducer unit, thereby inputting first and second electric signals thereto, which comprises the steps of generating at least one third electric signal in dependency from mutual phasing of the first and the second electric signals, said phasing being multiplied by a constant or a frequency-dependent factor and further from a fourth electric signal which depends from at least one of the first and the second electric signals; generating the output signals of the transducer unit in dependency of the third signal and further from a fifth electric signal which is dependent from at least one of the first and the second electric signals.

Thereby, it becomes possible, irrespective of the actual physical mutual distance of the two converters, to select said de- _,..,jaRYT ~S~U WO 99/04598 PCT/IB98/01069 6 pendency, thereby pre-selecting same and possibly tuning and adjusting same, to result in a dependency as if the at least two converters were physically arranged at completely different physical positions than they really are.

In a first preferred manner of realising the inventive method the fourth electric signal is selected to be linearly dependent only from one of the first and second electric signals, thereby being preferably directly formed by such first or second electric signal.

Nevertheless, in a today's more preferred manner of realising the inventive method, the fourth electric signal is dependent on both first and second electric signals. In a preferred form the fourth electric signal has a predetermined or adjustable "lobe" characteristic, i.e. dependency from spatial impinging direction. Thereby in a preferred form of "lobe" realisation the fourth electric signal is generated by delaying one of the first and second signals and then summing the delayed signal and the other, undelayed signal of said first and second signals. Thereby, the fourth electric signal per se has an amplification to impinging angle dependency and thus defines as was said for a "lobe", as an example according to a dependency as was discussed with the help of the figs. 1 to 4.

In a further preferred form of realising the inventive method, either per se or combined with either method to generate the fourth signal as just stated, and especially combined with generating the fourth signal with a "lobe"-characteristic, it is proposed to generate the fifth electric signal in direct or linear dependency of at least one of the first and second elec- WO 99/04598 PCT/IB98/01069 7 tric signals, thereby preferably using one the said first and second electric signals as the fifth electric signal.

Thereby, and again per se or combined with either method of generating the fourth electric signal, especially combined with generating the fourth electric signal with a "lobe"-dependency, it is proposed to generate the fifth electric signal as well with a "lobe" dependency from spatial impinging angle, which is realised in a first form by delaying one of the first and second signals and summing the delayed signal and the other of said first and second signals. Thereby, it becomes clear that the fourth electric signal, generated to define for a "lobe" characteristic, may directly be used as the fifth electric signal, having then the same "lobe"-characteristic.

In a further, clearly preferred realisation form of the inventive method and combined with any of the preferred realisation forms stated up to now and throughout the further description, it is proposed to generate the first and second electric signals in their respective spectral representation, thereby generating the at least one third electric signal in dependency of mutual phasing of respective spectral components of the first and second signals and multiplied by a constant frequency-independent or by frequency-dependent factors.

In a further preferred mode of operation, the frequencydependent multiplication factors are selected to be inversely proportional to frequency, at least in a first approximation.

With an eye specifically on hearing aid applications, wherefore the present method is most suited, but may be clearly applied to others, it is proposed that the real physical distance of the first and second converters to be at most 20 mm, whereby lw_ WO 99/04598 PCT/IB98/01069 8 the virtual distance, which is at least dependent from the phasing multiplication factor, is selected to be larger than the mutual physical distance of the two converters, in other words dependency of the transducer unit's output-signal from spatial angle becomes so as if, physically, converters were provided at considerably larger mutual distances than they really are. It goes without saying, that such technique is of very high advantage in any space-restricted applications, as especially in hearing aid applications.

To resolve the object mentioned above and to realise especially a hearing aid, whereat, irrespective of the physical position of at least two acoustical/electrical converters, a desired reception lobe may be tailored and possibly adjusted according to the needs, is realised inventively by an acoustical/electrical transducer apparatus comprising at least two acoustical/electrical converters spaced from each other by a predetermined physical distance, whereby the at least two converters generate, respectively, first and second electrical output signals and wherein the outputs of said acoustical/electrical converters are operationally connected to an electronic transducer unit, which generates an output signal dependent from said first and second output signals of said converters by an amplification function which function is dependent from spatial angle under which said converters receive acoustical signals, comprising: a phase difference detection unit, the inputs thereof being operationally connected to the outputs of said converters and generating at its output a phase difference-dependent signal, WO 99/04598 PCT/IB98/01069 9 a phase processing unit, one input thereof being operationally connected to the output of said phase differencedetection unit, at least one second input of said processing unit being operationally connected to a factor-valueselecting source, a third input of said phase processing unit being operationally connected to at least one of the inputs of said at least two converters, said phase processing unit generating an output signal at its output according to a signal at said third input with a phasing according to a signal at said one input and at said at least one second input, a beam-former processing unit with at least two inputs, one input being operationally connected to the output of said phase-processing unit, the second input being operationally connected to at least one output of said at least two converters.

Under all the aspects of the invention there is thus possible to realise Pv Pp.

This especially for low-space applications, as especially for hearing aid applications.

Thereby, there is introduced the virtual distance Pv of transducers, i.e. the distance of converters which would have to be physically realised to get an angle dependency as realised inventively.

Thereby, according to formula f, may be shifted to lower frequencies: WO 99/04598 PCT/IB98/01069 10 It becomes possible to realise f, values well in the audiofrequency band for speech recognition 4 kHz) with physical distances of microphones, which are considerably smaller than this was possible up to now.

Multiplying the phase difference by a constant factor does nevertheless not affect the roll-off according to fig. 4. This roll-off is significantly improved, leading to an enlarged frequency band B, according to fig. 4 if as was said the predetermined function of frequency is selected as a function which is at least in a first approximation inversely proportional to the frequency of the acoustic signal.

For instance for the first order cardoid according to fig. 3 and fig. 4, there may be reached a flat frequency characteristic between 0,5 and 4 kHz and thus a significantly enlarged frequency band Br with well-defined roll-offs of amplification at lower and higher frequencies by accordingly selecting the frequency dependent function to be multiplied with the phase difference.

Other objects of this invention will become apparent as the description proceeds in connection with the accompanying drawings, of which show: Fig. 1: A functional block diagram of a two-transducer acoustic receiver with directional beam forming according to prior art; Fig. 2: one of prior art beam forming techniques as may be incorporated in the apparatus of fig. 1, shown in block diagram form; -'-~-iiCLi-i;ii;i WO 99/04598 PCT/IB98/01069 11 Fig. 3: a two-dimensional representation of a threedimensional cardoid beam, i.e. amplification characteristic as a function of incident angle of acoustical signals; Fig. 4: the frequency dependency of the maximum amplification value according to fig. 3 for first and second order cardoid functions; Fig. 5: a pointer diagram resulting from the technique according to fig. 2, still prior art; Fig. 6: a pointer diagram based on fig. 5 (prior art), but according to the inventive method, which is performed by an inventive apparatus; Fig. 7: a simplified block diagram of a first realisation form of an inventive apparatus, especially of an inventive hearing aid apparatus, wherein the inventive method is implemented; Fig. 8: a simplified block diagram of a today preferred realisation form of the inventive method and apparatus; Fig. 9: a simplified block diagram of an inventive apparatus, operating according to the inventive method, in a generalised form; a generic signal-flow/functional block diagram of an inventive apparatus operating according to the inventive method; Fig. 10: WO 99/04598 PCT/IB98/01069 12 Fig. 11: the measured directivity characteristics resulting from the inventive method and inventive apparatus according to fig. 8; Fig. 12: a second directivity characteristics in a representation according to fig. 11, resulting from the inventive method and apparatus according tp fig. 8.

As was mentioned above, in the figs. 1 to 4 known beam forming techniques were based on at least two acoustical/electrical transducers spaced from each other and directly on their mutual physical distance p,p.

In fig. 5 there is shown a pointer diagram according to The basic idea of the present invention shall be explained now with the help of the still simplified one C frequency example. The inventively realised pointer diagram is shown in fig. 6. The phase difference o dt between signal A 2 and A, according to fig. 6 is Ppsin6 o dt Ap.

This phase difference is determined and is multiplied by a value dependent from frequency, thus with the respective value of a function M(co), which may be also a constant M 0 1.

By phase shifting one of the two signals A, according to the respective pointers in fig. 6, e.g. of A 2 by M, Ap or by M 0 Ap, there results the phase shifted pointer Av,. This pointer would have also occurred if dt had been larger by an amount according u~j~u~ r..I 'M WO 99/04598 WO 9904598PCT/1B98/01 069 13 to M, or Mot thus if a "virtual transducer,!- had been placed distant from transducer by the virtual distance for which: (11) Pv MI, or (12) Pv o' p As we consider one single frequency for simplicity we may write MO= MI.

With virtual TV, (13) TV, 'T and sine (3v) dtv M. pp we get according to the present invention: A, Asinot

A

2 Asinco(t+dtv) Asino(t+M 0 dt) Asino(t+M.T) (6v) Arv=2Asin co(T-dt) /2) With we further get: Therefrom, we may see that f or a given pp, which would lead to a too high fr' frv is reduced by the f actor taken M, 1.

In fig. 7 there is schematically shown a first preferred realisation form of an inventive apparatus in a simplified manner, I, I 7 2 ~P!17' ~MW~ WO 99/04598 PCT/IB98/01069 14 especially for implementing the inventive method into an inventive hearing aid apparatus. Thereby, the output signals of the acoustical/electrical transducer 2 a and 2 b are fed to respective analogue to digital converters 20a, 20b, the outputs thereof being input to time domain to frequency domain TFC converter units as to Fast-Fourier Transform units 22a and 22b.

A spectral phase difference detecting unit 27 spectrally detects phase difference Ap for all n spectral frequency components which are then multiplied by a set of constants If M is a function of o, then the c, can be different for different frequencies, and represent a frequency dependent function or factor. If on the other hand the phase differences A(P are multiplied by the same c o cn 1 this accords with using a constant M 0 This multiplication according to is done at a spectral multiplication unit 28. Signal A, in its spectral representation is then spectrally phase shifted at a spectral phase shifter unit 29 by the multiplied spectral phase difference signals output by multiplier unit 28.

According to fig 7 the signal A, in its spectral representation and inventively, spectrally phase shifted A,(o,Ap' n is computed in a spectral computing unit 23 together with A 2 in its spectral representation, as if transducer 2a was distant from transducer 2b by a distance Pv Mp. The resulting spectrum is transformed back by a frequency to time domain converter FTC as by an Inverse-Fast-Fourier-Transform unit 24 to result in A,.

WO 99/04598 PCT/IB98/01069 15 Thereby, other beam forming techniques than that described with the help of figs 1 to 4, i.e. using the time delaying technique transformed in the frequency domain may be used in unit 23.

Nevertheless the time delaying technique is preferred.

With an eye on fig. 4 it has been explained that by inventively introducing "virtual" converters with a virtually enlarged mutual distance, it becomes possible to shift the high gain frequency f, towards lower frequencies, which is highly advantageous especially for hearing aid applications. This is already reached if instead of a frequency dependent function a constant M 0 is multiplied with the phase difference as explained.

In a preferred mode of the invention the frequency dependent function M, is selected to be, at least in a first approximation, (14) M, Thereby, it is reached that, different from fig. 4, there will be no roll-off and the gain in target direction will be constant over the desired frequency range. By appropriately selecting the function M. it is e.g. possible to reach a flat characteristic within a predetermined frequency range, e.g. between 0.5 and 4 kHz with defined roll-offs at lower and higher frequencies. With appropriately selecting the function M, practically any kind of beam forming can be made.

For generating higher order cardoid weighing functions it is absolutely possible to additionally use the not phase-shifted output signal A, as shown in fig. 7 by dotted line as com- I 1 4-WMW, Mw 11~ 1-1 WO 99/04598 PCT/IB98/01069 16 puting input signal to unit 23 too, thus "simulating" three converters.

Fig. 8 shows a today's preferred embodiment of an inventive apparatus in a functional-block/signal-flow representation in analogy to the representation of fig. 7. Blocks and signals which were already explained with the help of fig. 7 are defined in fig. 8 by the same reference numbers.

The phase spectrum at the outside of multiplication unit 28, is added at a summing unit 29' to a signal Akr, n 0 also in spectral representation, which signal has a preselected dependency from impinging angle 8, as especially a first or higher order cardoid dependency.

To realise that signal and following the explanation with respect to figures 2 to 4, the output signal and A 2 in their spectral representation, are led to a beamformer unit 32, which may be integrated in beam-former unit 23' and which e.g. is built up according to the beam-former of fig.

2. Thereby, it must be clearly stated that instead of the beamformer 32 as shown in fig. 8 other kinds of beam-former resulting in different than first order cardoid characteristics may be implemented there.

The spectrum Akr,...n(0 n,6) is then phase-shifted by the phase adding unit 29' by A(p' 1 resulting in an output signal of that unit 29' which is the spectrum A, n,Ap' 1 n,6) as shown in fig. 8. The signal as well as the output signal of summing unit 29' are led to the beam-former unit 23', where they are preferably again summed as shown at 33.

,A.9tMVA i 4~ WO 99/04598 PCT/IB98/01069 17 At the output of beam-former unit 32 a signal is generated with a real cardoid dependency from impinging angle 8, whereas at the output of unit 29', and thus after phase shifting, a dependency function with respect to impinging angle 0 is realised according to virtually positioned converters. When summing, as with the unit 33 within beam-former unit 23', there results a dependency of the output signal Ar from impinging angle 0 according to a second order cardoid if the real cardoid dependency at the output of unit 32 is a first order cardoid.

Thus, in a more generic representation, as shown in fig. 9, the phase difference spectrum at the output of unit 27 is subjected to a phase shifter unit 35, where it is modified as per c, to

C

n The generalised phase shifter 35 may receive directly one of the output signals of one of the two converters 2a, 2b and/or a signal which results from beam forming from the said converter output signals to be phase shifted. In fig. 9 this is represented by the signal path fed back from beam former 37 to the phase shifter 35. This feedback accords, with an eye on fig. 8, to the signal path between beam former 32 and summing unit 29' According to fig. 9 beam former unit 32 of fig. 8 is integrated in the overall beam former unit 37.

The beam former 37 in its generalised form of fig. 9 receives at least one of the output signals of the converters 2a, 2b and the output signal of the generalised phase shifter It is evident for the skilled artisan that more than two real converters may be used and/or I WO 99/04598 PCT/IB98/01069 18 9 more than one function or of c o or n sets may be used to produce more than one "virtual transducer" signal from one or from more than one real converter signals respectively.

With selecting the number of physical and virtual converters, their characteristics and virtual "relocation" of these converters, the spatial weighing function may be selectively tailored.

The present invention under its principal object makes it possible to realise practically any desired beam forming with at least two converters separated by only a predetermined small distance, due to the fact that electronically there is provided a virtual mutual converter location of the physically provided converter.

Thereby, roll-off may be significantly reduced by such virtual transducer, which is especially established with realising a virtual distance of the converter which is dependent from frequency, especially inversely dependent. By selecting a frequency-M,, -dependent virtual distance of the converters, virtually an array of frequency-selective converters is established.

For a hearing aid apparatus the real distance between the at least two transducers, i.e. microphones, is selected to be mm at most, preferably less.

Fig. 10 shows in most generic form the principle proceeding and apparatus structure as according to the present invention and common to all embodiments of the invention as described above.

First and second electric signals S, and S which are derived from the output signals of the at least two acoustical/electrical converters 2 a, 2 b, are input to the transducer unit 3.

WO 99/04598 PCT/IB98/01069 19 Within unit 3, there is provided a phase difference detection unit according to unit 27 of figures 7, 8 or 9. The phase difference detection unit 27 has respective inputs which are operationally connected to the inputs of unit 3 and- thus to the outputs of the converters 2a, 2b. The output of the phase difference detection unit 27 is operationally connected to an input of a phase processing unit 40 shown in dashed-dotted lines in fig. 10. The phase processing unit has a second input, which is connected to a factor value-selecting source 42, generating a constant or frequency-dependent factor h. A third input of the phase processing unit is operationally connected as schematically shown by combining unit 44 in an "AND" or in an "EX- OR" dependency to respective outputs of the at least two converters 2 a and 2 b The phase processing unit 40 generates an output signal, S 3 in accordance with a signal, S 4 applied to the third input of the processing unit 40 and in accordance with the signals applied to the first from 27 and second from 42 inputs to the phase processing unit.

The signal at the first input of the phase processing unit, which is operationally connected to the output of the phase difference detection unit, is multiplied by unit 28 by the constant or frequency-dependent factor, and, at a signal combining unit 46, the output signal of the processing unit, signal S 3 is thus generated in dependency from mutual phasing of the output signals of the converters, multiplied by a constant or frequency-dependent factor and from signal S, as applied to the third input of the processing unit 40, which latter signal

S

4 is dependent from at least one of the output signals of the converters 2 b In unit 46 the dependency F, of signal S 3 122i"_ZW WO 99/04598PC/B8006 PCT/IB98/01069 20 from both, signal S, and multiplied phasing signal as at the output of unit 28, is generated.

The signal S,1 which accords to A, of fig. 7 or. to Ak, I .n (c 1 n1) of figs. 8 and 9, is input to a beam former processing unit 48 according to unit 23 or 23' or 37, as of the figs. 7 to 9. The beam former processing unit comprises a second input to which dependent from at least one of the output signals of the converters 2 b is fed. Latter signals are thus operationally connected as schematically shown by block in an "1EX-OR"1 or in an "AND" combination to the beam former processing unit 48.

In fig. 11 there is shown the "lobe" or directivity characteristic in dB which was measured at an inventive apparatus according to fig. 8 at single frequency 1 kHz of acoustical signals impinging on the two acoustical/electrical converters 2 a, 2 b' In this apparatus there was valid: converters 2 2 b: omnidirectional microphones, KNOWLES EK 7263 Physical distance pp: 12 mm T 35 j.sec.

c: ~2 at 1 kHz and at 4 kHz There resulted a directivity index as defined in SPEECH COMMU- NICATION 20 (1996), 229 to 240, Microphone array systems for hands-free telecommunication, Gary W. Elco of 8.83.

In fig. 12 the result is shown at an inventive apparatus which was used for the measurement according to fig. 11, but at 4 kHz WO 9?/U4598' PCT/IB98/01069 21 single frequency acoustical impinging signals. The directivity index became 7.98.

There results from proceeding according to fig. 8 a directivity characteristics according to a second order cardoid. This would conventionally have to be realised by means of four acoustical/electrical converters as of 2a and 2 which four converters define for a spacing of 24 mm between respective two of the four converters. Thus, it might be seen that with the inventive method and apparatus with only two acoustical/electrical converters with a mutual spacing of 12 mm a directivity result is reached as if four acoustical/electrical converters had been used with mutual spacing of 24 mm.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or in any other country.

For the purposes of this specification it will be clearly understood that the word "comprising" means "including but not limited to", and that the word "comprises" has a corresponding meaning.

Claims (17)

1. A method for electronically selecting the dependency of an electric output signal of an electronic transducer unit from spatial direction wherefrom acoustical signals impinge on at least a first and a second acoustical/electrical converter op- erationally connected to the input of said transducer unit and thereby inputting first and second electric signals thereto, comprising the steps of generating at least one third electrical signal in dependency from mutual phasing of said first and second electric signals multiplied by a constant larger than unity or a frequency- dependent factor and further from a fourth electric signal which is dependent from at least one of said first and second electric signals, thereby generating by said multiplying a mutual phasing of said first and second electric signals as if said first and second converters were more distant from each other than they actually are; generating said output signal of said transducer unit in de- pendency of said third electric signal and a fifth electric signal being dependent from at least one of said first and second electric signals.

2. The method of claim 1, thereby generating said fourth electric signal as a signal dependent from said first or second electric signal.

3. The method of claim 1, thereby generating said fourth electric signal as dependent from said first and said second electric signals. P13637.1PC.1 22 a

4. The method of claim 1, thereby generating said fourth electric signal as a signal with a predetermined or adjustable dependency from said spatial direction, as with a cardoid de- pendency. P13637.1PC.1 23 The method of claim i, thereby generating said fourth electric signal by delaying one of said first and second electric signals and summing the delayed signal and the other of said first and second signals.

6. The method of any one of claims 1 to 4, thereby generating said fifth electric signal as being dependent from one of said first and second electric signals.

7. The method of any one of claims 1 to 4, thereby generating said fifth electric signal as dependent from both said first and said second electric signals.

8. The method of any one of claims 1 to 5 or 7, thereby generating said fifth electric signal as a signal i ~with a predetermined or adjustable dependency from said spatial direction, as with a cardoid dependency.

9. S 9. The method of any one of claims 1 to 5 or 7 or 8, thereby generating said fifth electric signal by delaying one of said first and of said second signals and summing said delayed signal and the other of said first and second signals.

10. The method of any one of claims 1 to 9, thereby generating said fourth electric signal by generating said fifth electric signal. S11. The method of any one of claims 1 to 10, thereby 30 generating said first and second electric signals in their respective spectral representation and generating said at least one third electric signal in dependency of mutual phasing of respective spectral components of said first and second signals, multiplied by said factor and in dependency of said fourth electric signal. \\melbfiles\home\Priyanka\Keep\speci\79281-98doc 9/05/02 b i 24

12. The method of any one of claims 1 to 11, thereby selecting said factor as inversely proportionalto frequency.

13. An acoustical/electrical transducer apparatus comprising at least two acoustical/electrical converters spaced from each other by a predetermined physical distance, whereby the at least two converters generate, respectively, first and second electrical output signals and wherein the outputs of said acoustical/electrical converters are operationally connected to an electronic transducer unit, which generates an output signal dependent from said first and second output signals of said converters by an amplification function which function is de- S* pendent from spatial angle under which said converters receive acoustical signals, comprising: °o a phase difference detection unit, the inputs thereof being operationally connected to the outputs of said converters and generating at its output a phase difference-dependent signal, a phase processing unit, one input thereof being operation- ally connected to the output of said phase difference- detection unit, at least one second input of said processing S 20 unit being operationally connected to a factor-value- selecting source, a third input of said phase processing unit being operationally connected to at least one of the outputs of said at least two converters, said phase processing unit generating an output signal at its output according to a signal at said third input with a phasing according to a sig- nal at said one input i "t said at east one second input, a beam-former processing unit with at least two inputs, one nput being operationally connected to the output of said .ase-processing unit, the second input being operationally ~N i 25 connected to at least one output of said at least two converters.

14. The apparatus of claim 13, wherein said factor value- selecting source generates a constant or frequency- dependent signal values. The apparatus of claim 13 or 14, wherein said third input of said phase-processing unit is operationally connected to one output of said at least two converters.

16. The apparatus of any one of claims 13 to 15, wherein said third input of said phase-processing unit is connected to the output of a beam former unit, the inputs thereof being operationally connected to the outputs of said at ~least two converters. 0 17. The method of claim 16, said beam former unit comprising a further summing unit, one input thereof being 20 operationally connected to an output of one of said at least two converters, the other input thereof being operationally connected via a time-delay unit to the output of the other of said at least two converters. 25 18. The apparatus of any one of claims 13 to 17, wherein said second input of said beam-former processing unit is operationally connected to one of said at least two converters. o "30 19. The apparatus of any one of claims 13 to 18, wherein said second input of said beam-former processing unit is operationally connected to the output of a summing unit, one input thereof being connected via a time-delaying unit to the output of one of said at least two converters, a second input of said summing unit being operationally connected to the output of said second one of said at least TST two converters. \\meliles\homes\Priyanka\Keep\spec\79281-98.doc 9/05/02 26 The apparatus of any one of claims 13 to 19, wherein the outputs of said at least two converters are operationally connected to the inputs of a further summing unit, one thereof via a time-delay unit, the output of said further summing unit being operationally connected to said third input of said phase-processing unit and to said second input of said beam-former processing unit.

21. The apparatus of any one of claims 13 to wherein the outputs of said at least two converters are generated via respective analogue to digital converters and time domain to frequency domain transform units, said phase-difference detection unit, said phase-processing unit and said beam-former processing unit operating in frequency domain, the output of said transducer unit being generated via a frequency domain to time domain conversion unit.

22. The apparatus of any one of claims 13 to 21, being a hearing aid apparatus, said at least two converters 20 having a mutual physical distance of at most 20 mm.

23. The method of any one of claims 1 to 12 and substantially as herein described with reference to the accompanying drawings.

24. The apparatus of any one of claims 13 to 22 and substantially as herein described with reference to the accompanying drawings. Dated this 9th day of May 2002 PHONAK AG By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia \\melb-files\home$\Priyanka\Keep\speci\79281-98.doc 9/05/02 P