Patent Publication Number: US-8111848-B2

Title: Hearing aid with acoustical signal direction of arrival control

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior application Ser. No. 10/383,414, filed Mar. 7, 2003, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a hearing device and the control of signal transfer characteristics within the hearing device. 
     2. Description of Related Art 
     Different techniques are known by which an acoustical surrounding of an individual carrying a hearing device, such as a hearing aid, may be classified, and the transfer characteristic between an acoustical input signal to the device and its mechanical output signals is controlled according to a classifying result. See, for example, the following U.S. patent application publication numbers: 2003/0144838, 2002/0037087 and 2002/0090098. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is generically directed under a first aspect to the control of signal transfer characteristics of acoustical signals impinging upon the sensing area of a hearing device to electrical signals for driving at least one electrical/mechanical output converter of such a device. Under a second aspect, the present invention is directed to binaural hearing device systems which necessitate a communication link between a device arranged in or a adjacent one ear and a device in or adjacent the other ear of an individual. The one-ear device comprises at least an arrangement of input acoustical/mechanical converters whereas the other ear device at least comprises an output electrical/mechanical converter. Both aspects are thereby most preferably combined. 
     Under the first aspect, from the WO 02/32208 according with U.S. application Ser. No. 10/059,059, the WO 01/20965 accordingly the US application no. 2002-0037087 or from the WO 01/22790 according to US application no. 2002/0090098, different techniques have become known by which the acoustical surrounding of an individual carrying a hearing device and thereby preferably a hearing aid device, may be classified and the transfer characteristic between the acoustical input signal to such a device and mechanical output signal of such device is controlled or adjusted according to such classifying result. The present invention is directed to exploiting a specific criterion of acoustical surrounding of the individual and thus of the hearing device on one hand for producing or manufacturing a respective control signal for such transfer characteristic, and on the other hand for positively controlling such transfer characteristic of a hearing device. 
     According to the most generic aspect of the present invention under its first aspect such criterion of the acoustical surrounding is the angular location of acoustical sources within such surrounding. The above mentioned object of the present invention is resolved on one hand by a method for producing control signals or data at a hearing device for controlling the signal transfer characteristic of acoustical signals impinging on said device to electrical signals driving at least one electrical/mechanical output converter of said device which comprises the steps of generating first signals or data which are indicative of direction of arrival of acoustical signals impinging on a sensing area of the device and further generating said control signals or data in dependency of the first signal or data. Further, the object outlined above is resolved according to the present invention by a method of controlling a signal transfer characteristic of acoustical signals impinging on a sensing area to electrical signals driving at least one electrical/mechanical output converter of the hearing device, which comprises the steps of generating at said device first signals or data which are indicative of direction of arrival of acoustical signals impinging on the sensing area of such device and controlling the signal transfer with control signals or data in dependency of the first signals or data. 
     The angular positions of acoustical sources in the acoustical surrounding of the device are thereby determined by generating the first signals or data which are indicative of direction of arrival. As will be seen exploiting such direction of arrival DOA allows classifying the acoustical surrounding under many criteria additional to just angular localisation of acoustical sources. 
     In a most preferred embodiment of the present invention the control signal or data are realised in dependency of the first signals or data, in that a histogram is generated from a signal or data which depends from the first signal or data, and the control signals or data are generated in dependency of such histogram. By forming a histogram from signals which are indicative of DOA, the time evolution of the acoustical surrounding is monitored somehow like low-pass filtering. Short term variations of the acoustical surrounding are filtered out and there remains in the histogram information about more relevant and persisting characteristics of the acoustical surrounding. 
     Thereby an accurate estimation of the prevailing acoustical surrounding becomes possible. 
     In a further preferred embodiment of the present invention the histogram as generated is classified and different control signals or data are generated in dependency of the result of such classifying. 
     Classification of a histogram includes watching different characteristics of such histogram, for example peak-magnitude, peak-width, relative positioning of such peaks, time evolution etc. and establishing which characteristics of the acoustical surrounding lead to which characteristics or combination of characteristics in the histogram as a bases for appropriately setting or controlling the transfer characteristic of the device. Thereby the acoustical surrounding is considered related to the device which receives the acoustical signals so that not only different behaviours of the acoustical surrounding itself but additionally some behaviour of the device and thus of the individual in the acoustical surrounding may be evaluated or detected. 
     In a preferred mode of performing the methods of the present invention, the histogram function is classified according to at least one of the following aspects or criteria:
         how is the angular location and/or its evolution of an acoustical source with respect to the hearing device and/or with respect to other sources   what is the distance and/or its evolution of an acoustical source with respect to the device and/or with respect to other acoustical sources   which is the significance of an acoustical source with respect to other acoustical sources   how is the angular movement of the device itself and thus of the individual with respect to the acoustical surrounding and thus to acoustical sources.       

     The control signals or data are generated in dependency of the result of such classifying at least under at least one of said criteria i.e., in dependency of the answers electronically found under such criteria. In a further preferred embodiment of the methods according to the present invention, the hearing device is provided with a beamformer characteristic. Such a beamformer characteristic defines an amplification between an acoustical signal which impinges on the device&#39;s sensing area and an electrical signal or data in dependency of direction of arrival of the acoustical signal with respect to the sensing area. Accordingly, controlling the addressed signal transfer characteristic at least comprises controlling the beamformer characteristic. 
     By generating the first signal or data indicative of direction of arrival of an acoustical signal it is e.g. possible to determine whether the beamformer&#39;s amplification characteristic has its maximum at that angle which accords with the DOA angle. If it hasn&#39;t and if the source at the specific DOA is to be accurately tracked, the beamformer is e.g. adjusted to shift its maximum amplification angle so as to coincide with the DOA. Thereby source tracking is performed. In analogy a source under a detected DOA may be cancelled as at least momentarily of no interest, by shifting low- or zero-amplification of the beamformer to occur at the specific DOA of that source. 
     Also under this beamformer control aspect it is preferred to generate in dependency of the first signals or data (DOA-indicative) a histogram and controlling at least the beamformer characteristic of the device in dependency of such histogram. 
     With respect to the advantages of subjecting direction of arrival indicative signals to histogramming, the same prevails as was outlined above. 
     In analogy to the above addressed classifying technique, in a still further preferred embodiment, the histogram is classified and different control signals or data which at least control the beamformer characteristic are generated in dependency of the result of such classifying. Further, classifying the histogram comprises classifying the histogram under at least one of the following criteria:
         how is the angular location and/or its time evolution of an acoustical source with respect to the device and/or with respect to other sources   what is the distance and/or its time evolution of an acoustical source with respect to the device and/or with respect to other sources   what is the significance of an acoustical source with respect to other acoustical sources   how is the angular movement of the device itself with respect to the acoustical surrounding.       

     Thereby controlling at least the beamformer characteristic is performed in dependency of the result of the classifying, which comprises classifying under at least one of the above criteria. 
     Under a further most preferred embodiment, primarily directed to a binaural hearing device, the methods according to the present invention comprise the steps of generating the first electric signal in dependency of acoustical signals which impinge upon a first acoustical receiver. Second electrical signals are generated in dependency of acoustical signals impinging upon a second acoustical receiver. A first electrical/mechanical output converter is driven by a third electrical signal, whereas a second electrical/mechanical converter is driven by a fourth electric signal. By control signals or data generated according to the present invention, at least one of the following signal transfer characteristics is controlled and adjusted:
         transfer characteristic from the first electric signal to the fourth electric signal   transfer characteristic from the second electric signal to the fourth electric signal   transfer characteristic from the first electric signal to the third electric signal   and finally transfer characteristic from the second electric signal to the fourth electric signal.       

     Thereby considering the two acoustical receivers provided and the two electrical/mechanical output converters provided, by said transfer characteristics, the influence of each of the acoustical receivers upon each of the output converts may be controlled or adjusted respectively in a preferred realisation form. 
     Again in a preferred realisation form, the at least one transfer characteristic, or all the four transfer characteristics as mentioned, are controlled by exploiting a histogram of a signal which is dependent from at least one of the first and of the second electric signals, and thus from the acoustical signals impinging upon the first and/or second acoustical receivers. 
     In a still further embodiment such histogram is classified and the at least one of said transfer characteristics is controlled in dependency of the result of classifying. Thereby classifying is preferably performed at least under at least one of the above mentioned classification criteria. 
     In a most preferred embodiment of the method performed with at least two acoustical receivers and the two electrical/mechanical output converters, at least one head related transfer-function HRTF is reintroduced by respectively adjusting the at least one of said transfer characteristics. This is done in the transfer characteristics from the first signal to the fourth signal and/or from the second signal to the third signal. 
     As an example: 
     Whenever an acoustical source becomes or is angularly located so that, considered from one acoustical receiver, it appears acoustically shadowed or masked by the individual&#39;s head, whereas, considered from the other acoustical receiver it is directly acoustically seen, on one hand the acoustical signal to the first mentioned masked receiver will be significantly smaller than the acoustical signal impinging on the unmask receiver, so that reception of that acoustical signal at the unmask receiver will be more accurate, for example with respect to signal to noise. Therefore, it might be advantageous not only to drive the output converter adjacent to the unmask receiver primarily in dependency of its output signal, but also to drive the other output converter adjacent to the masked acoustical receiver primarily in dependency of that signal with high SNR. Nevertheless, in such a case, the signal transfer characteristic from the unmasked receiver to the output converter adjacent the masked receiver should re-establish the HRTF, i.e. the masking effect of individuals head, so as to allow the individual to perceive the acoustical signal of that source spatially correctly. 
     A hearing device according to the present invention and resolving the above mentioned object has an acoustical/electrical input converter arrangement with an output, an electrical/mechanical output converter arrangement with an input, a direction of arrival determining unit with an input operationally connected to the output of the acoustical/electrical converter arrangement which generates at an output a signal or data indicative of direction of arrival of acoustical signals impinging on the acoustical/electrical input converter arrangement. There is further provided a controlled signal transfer unit, the input thereof being operationally connected to the output of the acoustical/electrical input converter arrangement, the output thereof being operationally connected to the input of the electrical/mechanical output converter arrangement. The controlled signal transfer unit provides for controlled signal transfer between the input and the output and has a control input which is operationally connected to the output of the direction of arrival determining unit. 
     Further preferred embodiments of the methods and devices according to the present invention under its first aspect will become apparent to the skilled artisan when reading the following description of preferred embodiments of the present invention as well the appending claims. 
     Under the second aspect of the present invention, most preferably combined with the first one, from the WO 99/43185 a binaural hearing device system is known, wherein each device associated with an ear comprises an input acoustical/electrical converter and an output electrical/mechanical converter. There is further provided a communication link between the two devices whereby data or signals are cross communicated via such link which are respectively dependent from the output signals of the respectively provided acoustical/electrical input converters. Thereby before the respective converter output signals are applied to the communication link they are analogue/digital converted whereby there may be implemented in the respective analogue/digital converters some additional signal preprocessing. Further such a system is known from the US 2002-004695A1. Location of the communication link appears to be unambiguously defined. 
     Today&#39;s monaural hearing devices customarily have at least two input acoustical/electrical converters for beamforming purposes. The binaural system according to the WO 99/43185 may be tailored to provide beamforming by using the two input converters provided at the respective one ear attributed devices. Thereby, as outlined above, data are cross-transmitted via the communication link, which are possibly preprocessed but which comprise substantially more information than really needed. Further beamforming with two input converters placed one on each side of individuals head may be quite complex and inaccurate, for example, due to the head-related acoustical transfer functions HRTF which describe the effects of acoustical signals being “shadowed” by individuals head. Such shadowing occurs, dependent on direction of arrival of acoustical signals, asymmetrically with respect to both ears, which on one hand allows spatial perception, and on the other hand renders beamforming quite complex. 
     It as an object of the present invention under its second aspect to provide a binaural hearing device system and respectively a method for controlling such hearing device system, wherein the technique of providing at least two input acoustical/electrical converters at one ear&#39;s device is maintained, as known from monaural devices, and additionally there is nevertheless applied to the communication link only one signal or data which is thereby dependent from the output signals of both of the at least two input converters at one ear&#39;s device. Thereby a significantly reduced amount of data is transmitted via said link compared with a case where, following the concept of the WO 99/43185, output signals of each input converter are separately transmitted via the link. 
     This object is resolved by the binaural hearing device system according to the present invention which comprises a first device for one ear of an individual, a second device for the other ear, and a data/signal communication link between the first and the second device. The first device comprises at least a reception unit with at least two input acoustical/electrical converters and a signal processing unit. Inputs of the signal processing unit are operationally connected to the electrical outputs of the at least two converters. The signal processing unit generates, at a combined output, a signal which is dependent on both of its input signals. A signal link is provided at the output side of the signal processing unit. The signal link transmits data signals which depend upon the output signal of the signal processing unit. The second device, which is for the other ear, comprises at least an output electrical/mechanical converter. 
     As is known to the skilled artisan, there exist so called Complete-In-the-Channel, CIC-hearing devices whereat, due to complete introduction in the ear channel, only one input acoustical/electrical converter is provided. Thereby whenever instead of the device mentioned above with at least two input converters, a CIC with only one input acoustical/electrical converter is to be applied according to the present invention&#39;s general concept, significant information and data reduction is achieved before transmitting data to the communication link, in that a Wiener-Filter is provided between the output of the one input converter and the communication link. 
     As was mentioned above, the system according to the present invention provides, in one embodiment, the first device to be applied to one ear not having an electrical/mechanical output converter, and thus only having the at least two acoustical/electrical input converters in a reception unit. This embodiment might be most valid e.g. if on any reason it is not possible to apply a device with at least two input converters at that ear requiring hearing improvement. Thereby the second device does not comprise an input acoustical/electrical converter irrespective whether the first device has an output converter or not. 
     In a further preferred embodiment, an output electrical/mechanical converter provided at the first device is operationally connected to the output of the processing unit and is thus driven by a combined signal or data dependent on both outputs of the at least two input acoustical/electrical converters provided. 
     In a still further preferred embodiment, the system according to the present invention has the reception unit of the first device as a first reception unit. The first reception unit&#39;s at least two input acoustical/electrical converters are first acoustical/electrical converters. Additionally the signal processing unit of the first device is a first signal processing unit. 
     Further, the output electrical/mechanical converter at the second device is considered as a second output electrical/mechanical converter. The first device comprises a first output electrical/mechanical converter and the second device a second reception unit. 
     Thus both devices for each of the two ears have respective reception units and thus input acoustical/electrical converters and respective output electrical/mechanical converters. 
     Nevertheless, the second reception unit at the second device needs not necessarily have more than one input acoustical/electrical converter, although providing also there at least two input acoustical/electrical converters is preferred. 
     Further the communication link which is provided in all embodiments according to the present invention, for communicating between devices adjacent or in the respective ears, maybe wirebound and/or based on optical fiber and/or on wireless communication. 
     In a preferred embodiment, whenever both ears&#39; devices are equipped with input acoustical/electrical converters, both devices are equipped with at least two of such converters, which permits beamforming at both devices. Also, the second reception unit is equipped with a signal processing unit having inputs that are operationally connected to the electrical outputs of the second input converters of the second reception unit. This processing unit generates, at a respectively second output, a signal which is dependent on signals at both said inputs of the second signal processing unit, whereby the signal link is provided at the output side of the second signal processing unit. Thus, via the addressed signal or communication link, combined signals dependent respectively on the output signal of at least two input converters are bidirectionally transmitted from one device to the other and vice versa. 
     Thereby, and in a further preferred mode or embodiment, the output of the first signal processing unit is operationally connected to a first input of a weighting unit and the output of a second signal processing unit is operationally connected to a second input of the weighting unit. The weighting unit has a first output which is operationally connected to an input of a first output converter and has a second output which is operationally connected to the input of the second output converter. Thereby the weighting unit may be construed as decentralized, for example in both devices. The weighting unit has a control input and varies operational connection or signal transfer between the first input and the first output, the first input and the second output, the second input and the first output and finally the second input and the second output. Such signal transfers are controlled by a signal or data applied to the control input of said weighting unit. Thereby such operational connections between respective inputs and outputs are formed preferably frequency or frequency-band specifically, and the respective functions which are controlled independently from one another are possibly, but not necessarily, complex functions. 
     So as to determine how the operational connections between respective inputs and outputs at the weighting unit have to be controlled, especially according to the existing acoustical surrounding, the control input of the weighting unit is preferably connected to an output of a classification unit, which later has at least one input operationally connected to an output of at least one of the reception units. 
     In a further most preferred embodiment the first device comprises a beamformer unit which has a beamcontrol input and an output. Via the beamcontrol input, the directional characteristic of the beam as an amplification characteristic in dependency of the spatial angle at which an acoustical signal impinges on the device, may be varied. There is further provided a detection unit for detecting the direction of arrival of an acoustical signal which impinges upon the reception unit, which unit generates at an output an output signal in dependency of said direction of arrival. This output is operationally connected to the beamcontrol input of the beamformer unit so that, for example, a source of acoustical signal, the direction of arrival of which having been detected, may be more accurately tracked by accordingly directing a maximum amplification direction of the beam upon such a source. Accordingly, a source, for example a noise source, the direction thereof having been detected, may be cancelled by controlling the beam so that it establishes in that noise source direction minimum amplification. 
     As was mentioned above in a preferred embodiment there is provided a weighting unit whereat signal transmission between respective inputs and outputs is controlled. Thereby control of such signal transmission is made dependent from the result achieved in a classification unit, the input thereof being operationally connected to at least one output of at least one of the reception units. 
     Departing from this embodiment and in a further preferred mode there is provided at the system a determination unit for the direction of arrival of an acoustical signal impinging on at least one of the devices. The direction determination unit is interconnected between at least one input of the classification unit and at least one output of at least one of the reception units at the devices. 
     Thus, the classification which finally controls signal transfer at the weighting unit at least comprises classification of signals which depend on direction of arrival. Thereby, and as a further improvement of such embodiment, there is provided at least one histogram forming unit, the input thereof being operationally connected to at least one output of at least one of the reception units. The output thereof is operationally connected to an input of the classification unit. Thus, classification at least comprises classification based on a histogram result. Most preferably and with an eye on providing a direction of arrival determination unit, such histogram forming unit is provided with an input operationally connected to an output of the determination unit and an output operationally connected to the classification unit. Thereby classification at least comprises classification of a histogram function of a signal or of signals which identify such direction of arrival. 
     The object mentioned above still further is resolved by the method for controlling a hearing device system which comprises at least a reception unit at a first device for one ear, which has at least two input acoustical/electrical converters, and at least an output electrical/mechanical converter at a second device for the other ear. A communication link is provided between the first and the second devices. The method comprises the steps of generating in dependency of output signals of the at least two input converters a combined signal and transmitting such combined signal via the communication link. 
     For applying the method according to the present invention to CIC hearing devices, the method according to the invention comprises providing instead of the at least two input converters only one converter, and construing the first device as a device to be completely introduced into the ear channel. The method further comprises a step to treat the output of the one input converter by a Wiener-Filter, and transmitting signals dependent from the output of the Wiener-Filter via the communication link. 
     The present invention and the object thereof is further resolved by the method for producing a drive signal for a electrical/mechanical output converter of a binaural hearing device, which method comprises the steps of acoustical/electrical converting impinging acoustical signals at least two input converters of a device to be applied adjacent individuals&#39; one ear, transmitting a combined signal dependent from both said convertings via a link to a further device to be applied adjacent or in individuals&#39; other ear and generating the drive signal in dependency of the transmitted signal. 
     Further preferred embodiments of the methods and system according to the present invention under its second aspect will become apparent to the skilled artisan when reading the following description of preferred embodiments of the present invention as well as the claims. As mentioned above the invention under its first aspect is most preferably improved in being combined with the invention under its second aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention under both and combined aspects will now be further described with the help of figures. They show examples of preferred embodiments, namely: 
         FIG. 1  By a schematic, simplified functional-block/signal-flow representation, a first embodiment of the system according to the present invention and operated according the methods of the present invention; 
         FIG. 2  in a representation form in analogy to that of  FIG. 1  a further embodiment of the present invention; 
         FIG. 3  again in a simplified schematic functional-block/signal-flow representation a still further embodiment according to the present invention again operating according to the methods of the present invention; 
         FIG. 4  still in the same representation form a further embodiment of the present invention; 
         FIG. 5  by means of a simplified schematic functional-block/signal-flow representation a subembodiment for automatic beamcontrol e.g. to track acoustical sources and/or to cancel reception of acoustical sources. Such embodiment may preferably be incorporated within the embodiments according to the present invention; 
         FIG. 6  departing from a system or methods according to  FIG. 4  still in a simplified schematic functional-block/signal-flow representation an improved embodiment of such system or methods; 
         FIG. 7  by means of a simplified schematic functional-block/signal-flow representation a system or method for controlling a hearing device as a function of direction of arrival of acoustical signals as detected and preferably classified; 
         FIG. 8  examples of direction of arrival behaviours as appearing on a histogram function to explain some of more simple classification criteria as preferably exploited at the system or methods of  FIG. 7  as well as at systems or methods to be shown with the help of the  FIGS. 9 and 10 ; 
         FIG. 9  in form of a simplified schematic functional-block/signal-flow representation an improved and today preferred form of an embodiment of the system according to the present invention and of the methods according to the present invention; 
         FIG. 10  departing from the representation of  FIG. 9  a more detailed representation of such system or methods making use of direction of arrival detection as described in more details in the WO 00/68703 which accords with the U.S. application Ser. Nos. 09/636,443 and 10/180,585. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     According to  FIG. 1 , a system according to the present invention operating according to the method of the present invention, both under a first aspect thereof, is schematically shown by means of a simplified functional block/signal flow diagram in a minimal configuration. There is provided an acoustical reception unit  1  with at least two acoustical/electrical converters  3   a  and  3   b , both with a respective acoustical input and an electrical output. Reception unit  1  may incorporate e.g. respective analog to digital converters connected to the outputs of the converters  3   a ,  3   b , and time domain to frequency domain conversion units downstream such analog to digital converters. The reception unit  1  has a signal processing unit  4  for processing signals in dependency of the analog signals appearing at the outputs of the converters  3   a ,  3   b . Processing unit  4  generates at an output A 1  of reception unit  1  a signal or data which is a result of combined processing of signals dependent on the output signals of both converters  3   a  and  3   b : The output signal at A 1  depends on the output signals of both converters  3   a ,  3   b . This signal or data at output A 1 , possibly further processed at respective signal processing units (not shown), is transmitted to a transmission link  5 , which again may incorporate further signal processing. At the output side of transmission link  5 , a signal or data, which is dependent on the signal appearing at the output A 1  of unit  1 , is input to an input E 7  of an electrical/mechanical converter unit  7 . Unit  1  is applied adjacent or within one of an individual&#39;s ears, and unit  7  to the other. 
     The system as shown in  FIG. 1  is in a preferred embodiment a hearing aid system i.e. a therapeutical system. Unit  7  is thereby an outside-the-ear or an inside-the-ear converter unit or an implanted or implantable unit. By this minimal system, acoustical signals are received on one of an individual&#39;s ears and control hearing at the other ear. Such a system may be provided, where on any reasons, applying the reception unit  1  is not possible or difficult on that ear where hearing shall be improved or reinstalled. 
     The concept of applying a reception unit as of unit  1  at or adjacent one ear and transmitting signals or data dependent on the received acoustical signals at such reception unit to the other ear, for improving hearing at that other ear, this concept per se is considered inventive, irrespective of how the reception unit, signal link to the other ear and the other ear&#39;s converter unit  7  are conceived: Under this concept, only one ear is provided with an electrical/mechanical unit and no reception unit. The embodiments of  FIGS. 1 to 3  clearly fall under such concept. In any case, the link  5  may be electric wire based, optical fiber based or may be a wireless communication link. 
     The double-line arrows shown in  FIG. 1  and the following figures represent signal or data communication paths. Along such signal paths, additional signal processing by respective units may be established. The double-arrows may indicate a direct signal transmission, but rather stand for an operational connection, in which signals are transmitted and processed in direction of the arrow. 
     By the system according to  FIG. 1 , only data or signals are transmitted via transmission link  5 , which have been preprocessed as by combining signals of at least two acoustical to electrical input converters  3   a ,  3   b.    
     In  FIG. 2  there is shown in a representation, in analogy to that of  FIG. 1 , a second preferred embodiment, which only differs from that of  FIG. 1  in that unit  1  of  FIG. 1  is now conceived as a unit  10  to be applied completely within an individual&#39;s ear channel, a so-called CIC-device. As known to the skilled artisan such a CIC unit customarily has only one input acoustical to electrical converter  3   c . By means of a digital signal processing unit  11 , which is operationally connected e.g. via time domain to frequency domain converter and analog to digital converter to the analog output of converter  3   c , at least a Wiener-filtering is performed. The output signal or data of converter  3   c  is processed by a Wiener filter to result in significantly preprocessed data before being transmitted via communication link  5  to the electrical to mechanical converter unit  7 . In  FIG. 2 , the output A 11  of the CIC unit is provided to the communication link  5 . 
     In  FIG. 3  there is shown in a representation in analogy to that of the  FIG. 1  or  2  a further preferred embodiment of the system according to the present invention, which operates according to the method of the present invention. According to the system of  FIG. 3 , the difference to the system of  FIG. 1  is that the output A 1  of reception unit  1  is not only, via transmission link  5 , operationally connected to the input E 7  of the electric/mechanic converter unit  7  at the other of individual&#39;s ears, but output A 1  is additionally operationally connected to an electrical/mechanical converter unit  7   b , which is provided at the same ear as reception unit  1 . 
     It is evident that in dependency of the signals or data at output A 1 , the left ear and the right ear units  7   a  and  7   b  have to normally be operated differently. Thus there are generically installed different and/or differently operating signal processing units as on one hand between the output A 1  and link  5 , link  5  and input E 7a , and on the other hand between output A 1  and input E 7b  of unit  7   b . In the case of the embodiment of  FIG. 3  and as shown within a dashed line frame, the units  1  and  7   b  are preferably incorporated in a unitary hearing device, especially in a hearing aid device being a behind- or an in-the-ear hearing device. 
     Instead of providing a reception unit  1  with at least two input acoustical to electrical converters  3   a  and  3   b  as shown in  FIG. 3 , this unit may be construed according to unit  10  of  FIG. 2 , i.e. as a CIC-unit. 
     According to the embodiment of  FIG. 3 , there is in fact established a MASTER-acoustical control by reception unit  1  at one ear of the individual, whereas a hearing device without an input acoustical to electrical converter unit is operated at the other ear as a SLAVE device. 
     Departing from the system and method as explained with the help of  FIG. 3 , a further preferred embodiment of the invention under the first aspect thereof is shown in  FIG. 4 , still in a representation in analogy to that of the  FIGS. 1 to 3 . 
     According to the system of  FIG. 4  there is provided for the left ear of an individual a reception unit  1   L  and for the right ear a reception unit  1   R . Both reception units  1   L  and  1   R  are conceived with respect to signal or data processing as was explained with respect to reception unit  1  in context with  FIG. 1 . Instead of units  1   R  and  1   L  being conceived according to unit  1  of  FIG. 1 , one or both thereof may be conceived according to unit  10  of  FIG. 2 . A signal or data dependent from the signal or data at the output A 1L  of reception unit  1   L  is fed to an input E 9L  of a selection unit  9 . A signal or data which is dependent from the signal or data appearing at the output A 1R  of the right ear reception unit  1   R  is fed to an input E 9R  of the selection unit  9 . There is further provided a left ear electrical/mechanical output converter unit  7   L  and a right ear electrical/mechanical output converter unit  7   R . 
     The selection unit  9 , as schematically shown by a switching arrangement, has an output A 9L  and an output A 9R  respectively operationally connected to the inputs of output converters  7   L ,  7   R . Signals or data appearing at either of the outputs A 9L  or A 9R  may operationally be connected to both electrical to mechanical converter units  7   L  and  7   R . Under the control of a selection-control unit  12  and, as schematically shown in unit  9  by an arrangement of switches, the input E 9L  or the input E 9R  is operationally connected to both of the converters  7   L ,  7   R . Thereby, whenever the operational signal or data connection within selection unit  9  is established according to that switching position shown in  FIG. 4 , both converters  7   L  and  7   R  are operationally connected to the right ear reception unit  1   R , and therefore the right ear reception unit  1   R  is the MASTER. In analogy, unit  1   L  becomes MASTER whenever the units  7   L  and  7   R  are operationally connected to the input E 9L  of selection unit  9 . 
     In this embodiment again the right ear units  1   R  and  7   R  are preferably incorporated in a unitary right ear hearing device, be it a hearing aid device or be it a hearing device for other than therapeutical appliances. In analogy, the units  1   L  and  7   L  are incorporated in a respective left ear unitary device. Such hearing devices may thereby be in-the-ear or outside-the-ear hearing devices or their output converters  7   L  and/or  7   R  may be construed as implantable devices. Further, the right and left ear devices do not necessarily have to be of the same type, e.g. an in-the-ear and an outside-the-ear hearing device may be combined, an outside-the-ear and an implant device, etc. 
     Looking back on  FIG. 3  it has been shown that the acoustical signal impinging on unit  1  at one ear, e.g. at the left year, binaurally controls both electrical to mechanical output converter units  7   a  and  7   b . We have established that double-lined arrows stand for operational signal or data communication and not necessarily for direct connection. Thus, processing by processing units, such as DSP&#39;s, may be done along the operational connections. For example: As according to  FIG. 3  the acoustical signals impinging on unit  1  do control both output converters  7   a ,  7   b , and thus the head-related transfer function HRTF for the SLAVE side that is converter  7   a  is lost. Accordingly, there will preferably be provided as shown in dashed line a DSP  13  exclusively 
     influencing signals or data input to the SLAVE converter  7   a  and whereat the respective HRTF is taken into account. So as to properly set the processing parameters in DSP unit  13 , for taking the HRTF functions into account, the reception unit  1  detects direction of arrival DOA as denoted by γ in  FIG. 3 . There will be transmitted additionally to the signal or data dependent from those appearing at output A 1  of unit  1 , via link  5 , a DOA-significant signal or data to DSP  13  as shown by signal DOA. Further, there will be preferably provided a DSP  14  just upstream the input E 7b . DSP  13 , or a further DSP to input E 7a , as well as DSP  14 , will take in account different signal processing needs according to the hearing improvement needs at the respective ears. 
     When looking to the embodiment of  FIG. 4  in analogy to the just given explanations with respect to the system of  FIG. 3 , whenever the right ear device is MASTER, the HRTF will preferably be considered for the left ear converter  7   L , i.e. the SLAVE, and vice versa. Thus, the left ear HRTF is taken into account by a DSP  16 , and the right ear HRTF by a DSP  18 . Preferably the unit  1   L ,  1   R , which acts as a MASTER, provides data about direction of arrival DOA (not shown), so as to control the transfer characteristic of the respective HRTF DSP  16  and  18 . 
     With an eye on  FIG. 1  or  2 , there the processing unit  4  will preferably take the HRTF of the left side ear into consideration. 
     With respect to one preferred possibility for detecting direction of arrival DOA of acoustical signals at the reception units  1 ,  10 ,  1 L and  1 R, we refer to the WO 00/68703 “Method for localizing direction” of the same applicant, wherein a technique for detecting such direction of arrival DOA is completely disclosed, and which shall be incorporated with respect to DOA detection into the present description. This WO 00/68703 accords with U.S. application Ser. No. 09/636,443 and Ser. No. 10/180,585. Thereby, the reception units  1 ,  1 L,  1 R may preferably further comprise beam formers as are e.g. described in the WO 00/54553, according to U.S. application Ser. No. 09/267,742, the WO 99/04598, according to U.S. application Ser. No. 09/146,784, the WO 99/09786, according to U.S. application Ser. No. 09/168,184, all of the same applicant. 
     Thus, in one preferred embodiment such units  1 ,  1 L,  1 R provide for both, namely beam forming as well as detection of DOA. Thereby, in a further preferred embodiment beamforming is controlled by the DOA. 
     This preferred form of realizing the reception units  1 ,  1 L,  1 R, as discussed up to now, is schematically shown in  FIG. 5 . Thereby, the units  1 ,  1 L,  1 R comprise a beamforming subunit  20  with at least two input acoustical/electrical converters. At the output of such unit, which accords to output A 1  or A 1L , A 1R  there appear electrical data or signals in dependency of acoustical signals impinging on the at least two input converters and amplified according to a predetermined characteristic in dependency of the spatial angle with which the acoustical signals impinge on the input converters. The outputs of the acoustical to electrical converters are further exploited e.g. according to the teaching of the WO 00/68703, so as to provide for a signal which is indicative of the direction of arrival DOA of the acoustic signals. Thereby preferably, and as described in the WO 00/68703, there is performed a histogram of the DOA signals, as will be discussed later. The output of a histogram-forming and evaluating unit  22  controls beamformer unit  20  at a control input C 20  to, for example, track an acoustical source selected with high amplification or to delete such acoustical source by low amplification. 
     Turning back to the system of  FIG. 4 , it may be seen that the data link  5 , which was shown in the  FIGS. 1 to 3 , has not been shown anymore. Such data link, by which signals or data are or is transmitted from one ear side to the other, may be provided in the system as of  FIG. 5 , wherever felt best. The selection unit  9  may e.g. be incorporated in one of the left ear or right ear devices, e.g. in the left ear device, and then the addressed data link  5  will be provided at  5 ′ as shown in  FIG. 4 . On the other hand, the selection unit  9  may be split into left ear device- and right ear device-units, and then the data link  5  would be established and, following the representation of  FIG. 4 , practically within selection unit  9 . 
     Further, with an eye on  FIG. 4 , this system clearly operates one of the two devices as a MASTER, the other one, and thereby especially the output converter  7   L ,  7   R  thereof, as a SLAVE. Changing this MASTER/SLAVE relation occurs abruptly and it is not possible to gently control the MASTER/SLAVE weighting of the two devices. However, this becomes possible with an improvement to the embodiment of  FIG. 4 , which shall be explained with the help of  FIG. 6 . 
     According to  FIG. 6 , wherein units which correspond to units already described in context with  FIG. 4  have been denoted with the same reference number, the selection unit  9   W  in fact is a weighting unit. Therein, the influence of a signal or data dependent from the signal or data at output A 1L  upon signal or data respectively appearing at the outputs A 9L  and A 9R  is continuously adjustable, as shown schematically by variable coefficients α, β. In analogy the influence from output A 1R  upon the two outputs A 9L  and A 9R  of unit  9   W  is adjusted as schematically shown by variably controllable coefficients ε and δ. The coefficients α, β, ε, δ are preferably frequency dependent or at least dependent from frequency bands and are normally of complex value. These weighting coefficients are controlled by a selection control unit  12   W . 
     In the embodiments according to the  FIGS. 4 and 6  there is provided respectively a selection control unit  12  or  12   W  not having been described yet. The selection control unit  12  and respectively  12   W  are in fact classification units, wherein the instantaneously prevailing acoustical environment and/or the time development in the past up to the present of the acoustical surrounding and even a trend estimation for future development of such acoustical signals is classified according to predetermined criteria as e.g. disclosed in the WO 02/32208 which accords with U.S. application Ser. No. 10/059,059, or in the WO 01/20965 according to US application no. 2002-0 037 087 or in the WO 01/22790 according to US application no. 2002-0 090 098. In any case, there is input to the classifier and control units  12 ,  12   W  information about the acoustical signals received at units  1 ,  1   L  and/or  1   R  as shown at  133  in  FIG. 4 , and at  13   a ,  13   b  in  FIG. 6 . Under a second aspect of the present invention, a preferred classification technique shall be described below, which is most apt to be combined with the present invention under its first aspect described up to now. 
     This second aspect of the invention is schematically shown in  FIG. 7 , by a representation in analogy to that used throughout the  FIGS. 1 to 6 . It comprises a reception unit  30  with at least two input acoustical to electrical converters. The unit  30  operates so as to generate an output electrical signal or data at output A 30  indicative of the spatial direction of arrival DOA with which an acoustical signal impinges upon the acoustical inputs of the input converters  31   a  and  31   b  as provided. Such a unit is known e.g. from the WO 00/68703 which accords with the U.S. application Ser. Nos. 09/636,443 and 10/180,585 of the same applicant. From the instantaneously monitored DOA, a processing unit  32  generates a histogram function of DOA. This is also known from the WO 00/68703. Thus, under the second aspect of the invention, a histogram of the instantaneously prevailing DOA is formed. According to the second aspect of the invention it is the DOA-histogram which is used as an entity for classifying the acoustical signals in unit  34 , which impinge upon the unit  30  and for controlling system adjustment especially according to  FIG. 4 ,  5 , or  6 . Thereby and as schematically shown in  FIG. 7  by dashed lines, the reception unit  30  is preferably a part of a hearing device system  36 . The signals or data representing audio signals are generated by unit  30  at output A 230 , if that unit  30  performs combined tasks of DOA detection and audio signal processing. The histogram generated at unit  32  is now classified in classifying unit  34 , which controls at its output most generically the behavior of a hearing device system, be it a monaural system, but most preferably of a binaural hearing device system as shown in  FIGS. 1 to 6 . 
     Accordingly, in  FIG. 8  there is shown more than one output of the classifying unit  34 , representing different controls to the hearing device system according to different types of histogram appearance and thus of acoustical source behavior in the acoustical surrounding U of  FIG. 7  of the hearing device system, and thus of an individual carrying such system. 
     In  FIG. 8   a  there is shown purely as an example such a histogram function represented by the overall time, or in fact the overall number n of measured samples, which result in a specific DOA spatial angle γ. For the DOAγ 0 , a relatively sharp peak is present indicating that at that angle γ 0  to the acoustical input of the converters  31   a  and  31   b , there is a significant acoustical source in the acoustical surrounding U. At γ 1  there is a second yet less relevant acoustical source present in the surrounding U. 
     Departing from this histogram (a) some possible evaluations in time shall be discussed. According to  FIG. 8(   b ), at the DOA γ 0  the peak has become broadened and its amplitude has dropped. This means e.g. that the acoustical source at the angle γ 0  has become diffuse, which may be caused by an increase of distance between the reception unit  30  and the acoustical source in the surrounding U. According to  FIG. 8(   c ) and still considered as an evolution in time of the situation as present according to  FIG. 8(   a ), it may be seen that the histogram has been shifted by an angle Δ. This means that the reception unit  30  has rotated relative to the acoustical surrounding U, in other words that the individual carrying a system with unit  30  has turned his head by the angle Δ. This is identified because the relative positioning of the sources in the surrounding U according to  FIG. 8(   a ) at γ 0  and at γ 1  remains stable. 
     According to  FIG. 8(   d ), the peak appearing at the DOA γ 0  according to fig. (a) now appears at a different angle γ 2 , whereas the source of at γ 1  according to fig. (a) still appears at the unchanged angle φ 1 . This means that the source at γ 0  according to fig. (a) has moved to the new angular position γ 2 , whereby the reception unit  30  has not rotated, i.e. the individual has kept his head stationary. From these explanations it may be seen which kind of criteria are used in classifying unit  34  of  FIG. 8  to establish a relevant acoustical source, increasing distance, decreasing relevancy of a source, appearance/disappearance of a source, movement of individual&#39;s head relative to the acoustical surrounding, angular movement of a source in the surrounding U, etc. 
     By combining and adding further classifying criteria, an intelligent evaluation of the acoustical surrounding is performed, and by the respective results the behavior of the hearing device system  34  is controlled. This may include source tracking by controlling beamforming and/or, with an eye back on  FIGS. 5 and 7 , appropriate distribution of the influence or signal transfer of binaurally provided reception units upon binaurally provided output converters. 
     Thus, under the second aspect, the present invention is directed to classifying signals or data which are indicative of the DOA and controlling the status or behavior of a hearing device, be it a monaural or binaural device, in dependency of the classification result. Thereby most preferably, classification is performed upon data or signals wherefrom a histogram has been formed. 
     In  FIG. 9  there is shown a preferred embodiment, which combines the invention under its first aspect realized as was explained with the help of  FIG. 6 , and under its second aspect. 
     A left ear reception unit  40   L  of a left ear hearing device is conceived as a beamformer with at least two input converters  41   L ,  42   L . The right ear hearing device, as an example, is equally construed as the left ear device and thus comprises a reception unit  40   R , equal to the unit  40   L , and having at least two input converters  41   R  and  42   R . In analogy to the representation in  FIG. 6 , at the respective outputs A 1L , A 1R  electrical signals or data are generated as a result of processing the output signals of the converters  41   L ,  42   L ,  41   R ,  42   R . These signals A 1L , A 1R  are thus dependent on the acoustical signal impinging on the reception units, amplified according to the beamformer characteristics. The units  40   L ,  40   R  preferably comprise a respective beamformer control input BFC L  and BFC R , by which the shape of the beamformer characteristic, but especially the angle θ of maximal amplification may be adjusted. The units  40   L ,  40   R  further generate output signals, which are indicative of the DOA γ  of acoustical signals impinging on the acoustical inputs at the units  40   L ,  40   R . Signals or data dependent from these output signals DOA L , DOA R  are respectively input to histogram-forming units  44   L ,  44   R . The units  40   L ,  40   R  combined with histogram-forming units  44   L ,  44   R  may and are preferably realized as described in the WO 00/68703, which accords with the U.S. application Ser. No. 09/636,443. Thereby, and as seen in this paper, the beamformers are based on the delay-and-add/subtract principal and thus the beamformer control input BFC L  and BFC R  may e.g. adjust a delay τ. It is well-known to the skilled artisan that by establishing and varying the delay τ in a delay-and-add/subtract based beamformer, the direction θ of maximum/minimum amplification is varied, i.e. the reception lobe of the beamformer is angularly shifted. As also disclosed in the WO 00/68703 and also preferably applied to the present invention, signal processing is performed in frequency mode and frequency-specifically. At the output of the histogram-forming units  44 , the instantaneously prevailing DOA-dependent histograms are present and signals or data dependent there from are fed to a histogram classification unit  46 . Therein, the histogram courses resulting from acoustical signal reception at the left ear and the right ear are evaluated, thereby preferably including comparing the histogram courses as prevailing at the units  44   L ,  44   R . In unit  46 , on one hand the histogram courses per se are evaluated, e.g. and with an eye on  FIG. 8  on peaks, width of the peaks, time behavior of the peaks etc., and the acoustical surrounding with respect to acoustical sources therein is respectively classified, as e.g. under the aspect of “acoustical source moving away”, “acoustical source moving in the surrounding”, “acoustical source becoming less relevant”, “new acoustical source appearing”, “acoustical source disappearing”, “head of the individual moving”, etc. Additionally the interrelation of both histogram courses is evaluated, thereby detecting how one of the histogram courses alters or appears with respect to the other side&#39;s histogram course. This is, for instance, caused by the respective HRTF L  and HRTF R  becoming at the left and right ears (L, R) differently effective in dependency of DOA γ . Instead of performing classification on the basis of DOA according to the second aspect of the present invention, other classifications may be exploited as for instance described in the WO 02/32208 of the same applicant which accords with the U.S. application Ser. No. 10/059,059. 
     At the output of histogram classifying unit  46  there are generated control signals or data dependent on the classification result and from preset classification-dependent settings to be realized at the hearing device system. Thereby at the output of classification unit  46  a signal or data is generated, which is operationally connected to the beamformer control input BFC L  and BFC R . The classification unit  46  also generates a control signal or data input to the weighting unit  49 , which accords to the unit  9   W  of the system of  FIG. 6 . The beamformer control data and respective output is shown at BFC in  FIG. 9 . The weighting unit control signals or data and respective output of unit  46  is shown as SC. The SC signals or data do control, as was more generically shown in  FIG. 6  at the output of unit  12   W , the weighting unit  49  in that, shown by varying weighting coefficients α, β, ε, δ in  FIG. 6 , the weights or transfer functions with which the output signals at outputs A 1L , A 1R  respectively act upon electrical/mechanical converters  47   L  and  47   R . 
     To further explain the embodiment of  FIG. 9 , let us make an example. To start with there shall appear in the γ=0 DOA-direction with respect to the units  40   L ,  40   R  a significant acoustical source. The beamformers of the units  40   L ,  40   R  have their lobe directed on that source, so that γ=θ=0. Both histograms at units  44   L ,  44   R  may have e.g. a course as shown in  FIG. 8(   a ). The histogram classification unit  46  recognizes histogram peaks for γ=0 at both histograms, and this defines at unit  46  for a yet stable and significant acoustical source. Accordingly, by means of BFC, the beamformers are kept on θ=0. The SC control signal controls the selection unit  49  for equally weighted influence of signals or data appearing at both outputs A 1L  A 1R  upon the converters  47   L ,  47   R . 
     Now let&#39;s assume this relevant acoustic source in the acoustical surrounding U starts to move to the right-hand side of  FIG. 9 . This is recognizable at unit  46 , because both histogram courses will show a development according to  FIG. 8(   d ). Thus, unit  46  recognizes: “source is moving to the right”. As the acoustical source considered leads still to a significant sharp peak in both histogram courses, the beamformers of units  40  are both controlled by the control signals or data BFC to follow that source. Still the SC control signals control selection unit  46  at least nearly for equally distributed weighting of the influence of the output signals A 1L  and A 1R  upon the converters  47   L  and  47   R . 
     As the acoustical source moves further to the right the head-related transfer function HRTF starts to influence the acoustical signals impinging on the units  40   L ,  40   R . Whereas the right-hand side received acoustical signals will not be affected by the HRTF, the left-hand side received acoustical signals from that source become more and more influenced by HRTF, as the acoustical source becomes “hidden” by the individual&#39;s head H. Therefore, the histogram course at unit  44   R  will still have a pronounced peak representing the source considered, whereas due to the HRTF the histogram course at unit  44   L  will show at the angular position of the source considered, which is equal to the angular position of the peak in the histogram course at unit  44   R , a more and more enlarged, less pronounced peak. This is, purely as an example, shown in  FIG. 9  next to the histogram-forming units  44   L ,  44   R  and with respect to the same angular position γ S  of the acoustical source considered. The classifying unit  46  recognizes by comparing the two histogram courses that at the same angular position γ S , the left side histogram course has a widened and less pronounced peak with respect to the right-hand histogram course. This indicates an acoustical surrounding in which a moving acoustical source has moved so far to the right that the respective HRTF function becomes effective. This means that the data from that source processed in the left ear unit  40   L  becomes less accurate than the data from that source that is processed in the right ear unit  40   R  and, therefore, the selection unit  49  is controlled to react on this specific exemplified situation by increasing the influencing of the right side signals or data at output A 1R  upon the converters  47   L  and  47   R . Thereby and e.g. within unit  49  the HRTF L  function, which takes effect on the acoustical signals impinging upon the left side unit  40   L , will be maintained with respect to data operationally acting upon converter  47   L  in a most preferred mode, so as to maintain for the individual spatial perception of the acoustical source. With respect to beam control, as the DOA data of the right ear unit  40   R  becomes, according to this example, more accurate than the respective data from unit  40   L  e.g. due to higher level acoustic signals, beamformer control will also preferably be at least dominated by the DOA data from the right ear unit  40   R  (not specifically shown in  FIG. 9 ). 
     The weighting-coefficients or functions as of α, β, ε, δ of  FIG. 6 , are preferably complex valued, frequency or frequency band dependent functions. Also, in the classifier unit, multiple acoustical source situations are detected and predetermined strategies are set, how to control on one hand the beamformers, and on the other hand the signal transmission at weighting unit  49  most suitably for specific acoustical surroundings. 
     Thus, by combining the two aspects of the present invention, a binaural hearing device system is achieved, which incorporates “intelligent” system adjustment based on the evaluation of a DOA histogram course. 
     Once again it must be emphasized that the data or signal processing functions which have been explained as by  FIG. 9  may be split in a great variety of realization modes between the two hearing devices, or may be centralized within a unit remote from the hearing devices. Accordingly, the signal transmission link  5  from one ear side to the other will be provided. Further, the skilled artisan recognizes that the system of  FIG. 9  will incorporate different digital processing unit DSPs, especially along the double-arrowed operational connections, so as to take into account specific hearing improvement needs at both individual&#39;s ears, HRTF functions etc. 
     As we have mentioned before, one approach, which is today a preferred one, for and as a second aspect of the present invention, is to provide classification of the acoustical surrounding of an individual so as to appropriately control a hearing device, being it a monaural or a binaural hearing device, based on evaluation of the direction of arrival DOA. 
     An approach regarding how to determine the DOA is, as was explained before, explained in detail in the WO 00/68703. Based on that teaching, in  FIG. 10  there is exemplified a binaural hearing device system whereat on one hand and according to the first aspect of the present invention, combined data or signals from at least two input acoustical/electrical converters are respectively transmitting from one ear side to the other, or in the case of a CIC-device with one input converter after having been processed by a Wiener-Filter. On the other hand, the embodiment of  FIG. 10  incorporates also the second aspect of the present invention realised on the basis as disclosed in the WO 00/68703. A left ear reception unit  50   L  comprises two beamformers, one defining a maximum amplification characteristic in DOA=0° direction, and the other one in the backwards DOA=180° direction. In  FIG. 10  the beamformers are exemplified as being equal first order cardoid beamformers. 
     Unit  50   L  outputs at respective outputs A 50L1  and A 50L2  signals or data, which are dependent on the impinging acoustical signals amplified by the respective DOA dependent amplification of the beamformers, and which are frequency dependent. 
     These signals are respectively denoted in  FIG. 10  by S F1  and S B1 . These output signals are led after analogue/digital conversion (not shown) to time domain/frequency domain conversion units  52   L1  and  52   L2 , resulting in frequency specific output signals or data C B1  and C F1 . Signals dependent from the output signals of the conversion units  52  are further fed to absolute value forming units  54   L2  and  54   L1 , outputing respective frequency specific signals or data |C B1 | and |C F1 |. These absolute value signals or signals dependent there from, are fed to a quotient forming or division unit  56   L  outputing for left ear reception unit  50   L  a frequency specific quotient Q L . Signals or data dependent from that quotient Q L  are subjected to histogram forming in a histogram forming unit  58   L , which outputs histogram data H L . 
     As can be seen in  FIG. 10 , inputs to the quotient forming units are shown generically as N and Z. 
     The right ear side with right ear reception unit  50   R  up to data H R  is preferably construed exactly equally to the left ear side as just described and will therefore not specifically be described again. 
     The histogram data from the two histogram forming units  58   L  and  58   R  are input to a classifying unit  60 . 
     Further, signals dependent on the front-forwards beamformers at both reception units  50   L  and  50   R , namely |C F1 | and |C F2 |, are fed to a further quotient forming unit  62   V . Analogously, signals dependent from the output signal of the rear beamformers of both reception units, namely |C B1 | and |C B2 |, are fed to still further quotient forming unit  62   Re . Signals or data dependent from the result at the quotient forming units  62   V  and  62   Re  are input to respective histogram forming units  64   Re  and  64   V . The histogram data output by these histogram forming units are again input to the classification unit  60 . 
     After classification, for example as will be discussed below, the classification unit  60  generates output signals or data which are operationally linked to a control input of the weighting unit  61 . As a function of the classification result-data output by classification unit  60 , signal transfer within weighting unit  61  is controlled, namely:
         from an input E L1  to which signals dependent from the forward beamformer of unit  50   L  are fed to output A L  and output A R  respectively,   from an input E L2  to which signals or data dependent from the output signals of the rear beamformer of unit  50   L  are fed respectively to the output A L  and A R      and in complete analogy, from the right ear input E R1 , E R2  and to said respective outputs A L  and A R . The signals output at A L  and A R  are operationally fed to the output electrical/mechanical converters  63   L  and  63   R  respectively.       

     We Define: 
     
       
         
           
             
               Q 
               L 
             
             = 
             
               
                  
                 
                   C 
                   
                     F 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                 
                  
               
               
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                   C 
                   
                     B 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                 
                  
               
             
           
         
       
       
         
           
             
               Q 
               R 
             
             = 
             
               
                  
                 
                   C 
                   
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                     ⁢ 
                     
                         
                     
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                     2 
                   
                 
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                  
                 
                   C 
                   
                     B 
                     ⁢ 
                     
                         
                     
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                     2 
                   
                 
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               Q 
               Re 
             
             = 
             
               
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                   C 
                   
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                     ⁢ 
                     
                         
                     
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                     1 
                   
                 
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                     ⁢ 
                     
                         
                     
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                     2 
                   
                 
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               Q 
               V 
             
             = 
             
               
                  
                 
                   C 
                   
                     F 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                 
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                  
                 
                   C 
                   
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                     ⁢ 
                     
                         
                     
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     Let&#39;s discuss possible classification results and criteria exploited and generated at unit  60  whenever an acoustical signal source in the surrounding U is detected with different DOA&#39;s. 
     Whenever DOA γ is between 0° and 90°, the following is valid:
 
Q L &gt;1 and Q V &gt;1.
 
     It has to be noted that it is preferred to consider Q V  in this case rather than Q Re , because the acoustical signal impinges at the higher level on the forward beamformer of both units  50 , the output signals of these beamformers being thus more accurate with respect to signal/noise than the output signals of the respective rear side beamformers. 
     The same is considered with respect to evaluating Q L  or Q R , the signals leading to Q L  have a better signal/noise ratio than the signals leading to Q R  because, as the target acoustic source moves towards 90°, the right side HRTF more and more influences signals received at the right ear unit  50   R . These considerations are made also in the following cases to be discussed and are not repeated. 
     As the target source is located at the DOA γ between 90° and 180° the following is valid:
 
Q L &lt;1 and Q Re &gt;1.
 
     As the target source moves on to a DOA γ between 180° and 270° the following prevails:
 
Q R &lt;1 and Q Re &gt;1.
 
     Finally as the target source moves to a position between 270° and 360° the following prevails:
 
Q R &gt;1 and Q V &lt;1.
 
     Thus by evaluating these criteria, as a simplified example, within the classification unit  60 , an acoustical source&#39;s location is established around 360° and, accordingly, the respective signal transfer functions are set in weighting unit  61 . As an example: 
     If the source is detected by the above criteria to be located at a DOA between 90° and 180°, the rear side beamformer of left ear reception unit  50   L  will become master beamformer, because that beamformer outputs a signal with the best signal/noise ratio. Therefore, the transfer functions or coefficients according to  FIG. 6  from input E L2  on the one hand to A L  and on the other hand to A R  will govern. Thereby the transferred function from E L2  to A R  will consider the HRTF which is not influencing at the source position discussed signals impinging on the reception unit  50   L , but which must be considered for driving the right output converter  63   R  so as to maintain spatial source perception. Simplified, the forward beamformer of unit  50   L  and both beamformers at unit  50   R  become slaves and their respective output signals are merely exploited to generate the respective quotients to allow the classification unit  60  to properly classify the prevailing DOA, so as to properly control signal transfer in weighting unit  61 .