Patent Publication Number: US-8126153-B2

Title: Hearing system with partial band signal exchange and corresponding method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of German application No. 10 2008 015 263.3 filed Mar. 20, 2008, which is incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a hearing system for the binaural supply of a user with a first hearing apparatus and a second hearing apparatus. Furthermore, the present invention relates to a method for processing signals for a binaural supply with a first and a second hearing apparatus. The term “hearing apparatus” is understood here to mean any sound-emitting device which can be worn on or in the ear, like for instance a hearing device, a headset, earphones and suchlike. 
     BACKGROUND OF THE INVENTION 
     Hearing devices are wearable hearing apparatuses which are used to assist the hard-of-hearing. In order to accommodate numerous individual requirements, various types of hearing devices are available such as behind-the-ear (BTE) hearing devices, hearing device with external receiver (RIC: receiver in the canal) and in-the-ear (ITE) hearing devices, for example also concha hearing devices or completely-in-the-canal (ITE, CIC) hearing devices. The hearing devices listed as examples are worn on the outer ear or in the auditory canal. Bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The damaged hearing is thus stimulated either mechanically or electrically. 
     The key components of hearing devices are principally an input converter, an amplifier and an output converter. The input converter is normally a receiving transducer e.g. a microphone and/or an electromagnetic receiver, e.g. an induction coil. The output converter is most frequently realized as an electroacoustic converter e.g. a miniature loudspeaker, or as an electromechanical converter e.g. a bone conduction hearing aid. The amplifier is usually integrated into a signal processing unit. This basic configuration is illustrated in  FIG. 1  using the example of a behind-the-ear hearing device. One or a plurality of microphones  2  for recording ambient sound are built into a hearing device housing  1  to be worn behind the ear. A signal processing unit  3  which is also integrated into the hearing device housing  1  processes and amplifies the microphone signals. The output signal for the signal processing unit  3  is transmitted to a loudspeaker or receiver  4 , which outputs an acoustic signal. Sound is transmitted through a sound tube, which is affixed in the auditory canal by means of an otoplastic, to the device wearer&#39;s eardrum. Power for the hearing device and in particular for the signal processing unit  3  is supplied by means of a battery  5  which is also integrated in the hearing device housing  1 . 
     A hearing device system for the binaural supply of a person who is hard of hearing includes two hearing devices, one of which is worn on the left ear and the other on the right ear. If the two hearing devices communicate with one another in any fashion (e.g. by way of a wireless connection), this is referred to as a “binaurally coupled hearing system”. A binaurally coupled hearing system of this type has the possibilities of spatial signal processing, which is not possible using a monaural system, since with this system signals can be transmitted from one side to the other. 
     Approaches to binaural beam forming algorithms (beam forming) or blind separation algorithms (blind source separation) are known from the literature for instance. The element common to these known algorithms is that the necessary transmission capacity of the connection between the two devices has to be comparatively high since in order to calculate the output signal on the one side, both the overall input signal of the same side and also that of the other side are needed. A correspondingly high data transmission rate is thus needed for broadband communication, which is disadvantageous in respect of the high energy consumption associated therewith in the case of hearing devices. Only monaural methods are known as alternatives, which however are restricted as a result of the very minimal microphone distances above all in the case of low frequencies. Methods for realizing a directional microphone, a blind source separation, a feedback coupling reduction etc. are affected for instance. 
     Monaural methods of this type comprising one, two or more microphones per side indicate very good properties in respect of their performances such as interference noise suppression and noise performance in the case of higher frequencies (&gt;2 kHz). In the case of low frequencies, the noise problems occurring as a matter of principle (as a result of the inherent noise always present in the microphones in conjunction with the minimal microphone distance) nevertheless cannot continue. 
     The publication WO 99/431185 A1 discloses a binaural, digital hearing aid system, in which data is transmitted crosswise from the right to left and from the left to right hearing device. The data received by the other hearing device in each instance is processed binaurally using the actual data of the hearing device. If necessary, data is compressed prior to transmission. 
     The publication EP 1 771 038 A2 also discloses a method for operating a hearing aid device system for the binaural supply of a user. In frequency ranges, in which problematic feedback is to be expected, the input signals are transmitted crosswise to the other hearing device in each instance, so that an acoustic signal received by the microphone of a hearing aid device can be output via the receiver of the other hearing aid device in each instance following signal processing and amplification. As a result, the distance between a receiver and a microphone in each instance, between which a feedback path exists, is significantly increased for the relevant audio signals. 
     The publication WO 2004/114722 A1 also discloses a binaural hearing aid system with a coordinated sound processing. Here data relating to the classification of the sound environment is exchanged between both hearing devices. 
     SUMMARY OF THE INVENTION 
     The object of the present invention thus consists in providing a hearing system for the binaural supply of a user, in which data can be transmitted between two hearing apparatuses, in which the energy and/or computing outlay for the data exchange and/or the processing of the exchanged data is as minimal as possible however. Furthermore, a corresponding method for processing signals is to be provided. 
     This object is achieved in accordance with the invention by a hearing system for the binaural supply of a user with a first hearing apparatus including a first signal input facility for supplying a first input signal and a first communication facility, as well as a second hearing apparatus including a second signal input facility for supplying a second input signal, a second communication facility for receiving a signal from the first communication facility and a second signal processing facility for processing signals from the second signal input facility and the second communication facility to form a common output signal, with the signal transmitted from the first to the second communication facility corresponding to a real spectral part of the overall frequency spectrum of the first input signal, and with the transmitted part being binaurally processed in the spectral part of the overall frequency spectrum together with a signal from the second signal processing facility, while the signal from the second signal processing facility is monaurally processed by the second signal processing facility in the remaining part of the overall frequency spectrum. 
     Furthermore, provision is made in accordance with the invention for a method for processing signals for a binaural supply with a first and a second hearing apparatus by providing a first input signal in the first hearing apparatus, providing a second input signal in the second hearing apparatus, transmitting a signal from the first to the second hearing apparatus, processing the second input signal together with the signal from the first hearing apparatus in the second hearing apparatus to form an output signal of the second hearing apparatus, with the signal transmitted from the first to the second hearing apparatus corresponding to a real spectral part of the overall frequency spectrum of the first input signal, and with the transmitted signal being binaurally processed in the spectral part of the overall frequency spectrum together with a corresponding spectral part of the second input signal of the second hearing apparatus by the second hearing apparatus, while the second input signal of the second hearing apparatus is monaurally processed in the remaining part of the overall frequency spectrum by the second hearing apparatus. 
     Signals are advantageously prevented from being exchanged in full bandwidth between the two hearing apparatuses of a hearing system. Instead, only partial bands of the relevant signals are transmitted. As a result, the information flow and the computing outlay associated therewith is reduced to a minimum. 
     The first hearing apparatus preferably exhibits a first signal processing facility in order to process signals from the first signal input facility together with signals from the first communication facility, which originate from the second hearing apparatus, to form a common output signal. A mutual data exchange between the two hearing apparatuses is thus ensured. Even this intensive exchange of data may profit from a reduction in the transmission bandwidth. 
     The first and the second signal input facility may comprise at least two microphones in each instance. A beam forming or a high-quality directional microphone and/or a high-quality blind source separation can thus already be realized in the individual hearing apparatuses for instance. In order to then use the results for the spatial hearing, only the relevant spectral parts of these results are transferred to the other hearing apparatus in each instance. 
     It is particularly favorable for a low frequency part of the respective input signal to be exclusively transmitted during signal transmission between the two communication facilities. It is advantageous here for instance if the frequencies of the low frequency part lie below 1 kHz or 2 kHz. It is generally sufficient to exchange the low frequency parts in order to improve the binaural supply between the hearing apparatuses and/or hearing devices. 
     As was already indicated, a feedback coupling reduction algorithm, a beam forming algorithm or a blind source separation algorithm (blind source separation), which uses signals from the other hearing apparatus in each instance, can be implemented in the first and/or second signal processing facility. A significant saving in terms of computing outlay and energy consumption can thus be achieved particularly with these algorithms, in which the data exchange between the hearing apparatus brings significant advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in more detail with reference to the appended drawings, in which; 
         FIG. 1  shows the main design of a hearing device according to the prior art and 
         FIG. 2  shows a block diagram of an inventive hearing device system for the binaural supply. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The exemplary embodiment shown in more detail below represents a preferred embodiment of the present invention. 
       FIG. 2  shows a schematic representation of hearing device system with a left hearing device  10  and a right hearing device  20  for the binaural supply of a hearing device wearer  30 . The left hearing device has two microphones  11  and  12  in order to realize a directional microphone or to execute beam forming, blind source separation and suchlike. The output signals of the microphones  11  and  12  are each fed to a cross-over network  13 ,  14 . Each of these two cross-over networks  13  and  14  has a low pass filter output TP and a high pass filter output HP. Instead of or in addition to the microphones  11  and  12 , other signal input facilities, like for instance a telephone coil, a radio antenna and suchlike can also be used for instance. 
     The low frequency parts of the input signals from the cross-over networks  13  and  14  are fed to a binaural processing unit  15 . At the same time, the low frequency parts are fed to a transmitter  16  integrated into the hearing device in order to transmit them wirelessly to the right hearing device  20 . Conversely, a receiver  17  receives the low frequency part from input signals from the right hearing device and makes them available for the binaural processing unit  15 . The low frequency parts of the input signals of the left hearing device and of the right hearing device are binaurally processed together there and a low frequency output signal is generated. 
     The high-frequency parts of the cross-over networks  13  and  14  are fed to a monaural processing unit  18 . This unit generates a high-frequency output signal and supplies it to an adder and/or combining unit  19 . It links the high-frequency output signal of the monaural processing unit  18  to the low frequency output signal of the binaural processing unit  15  to form a common output signal SAL of the left hearing device  10 . This output signal SAL is optionally processed and/or fed to a receiver (not shown). 
     The right hearing device  20  is designed in symmetry with the left hearing device  10  in respect of the signal flow of interest here. It likewise exhibits two microphones  21  and  22 , the signals of which with cross-over networks  23  and  24  are split into high frequency and low frequency parts. The low frequency parts are processed on the one hand by a binaural processing unit  25  and are transmitted on the other hand from a transmitter  26  to the receiver  17  of the left hearing device. A receiver  27  receives the low frequency signals of the transmitter  16  from the left hearing device  10  and makes these available for the common processing with the low frequency parts of the right hearing device  20  in the binaural processing unit  25 . 
     The high frequency parts of the input signal are fed from the cross-over networks  23  and  24  to a monaural processing unit  28 . Like in the left hearing device  10 , the low frequency output signal of the binaural processing unit  25  and the high frequency output signal of the monaural processing unit  28  are then also combined here in a combining unit  29  to form a common process signal SAR of the right hearing device. 
     The two hearing devices  10  and  20  thus each exhibit a communication facility, namely a transmitter and a receiver  16 ,  17  and/or  26 ,  27  for bidirectional communication. There is basically also the possibility of only one monodirectional communication with a transmitter on the one side and a receiver on the other side being used, if this is advantageous for the binaural supply. Accordingly, a signal processing facility (e.g. binaural supply unit  15  or  25 ) would then also only be necessary in a hearing device. 
     In respect of the function of the hearing device system shown in  FIG. 2 , it is relevant in accordance with the invention for the input signals to be split into two frequency ranges, e.g. a low frequency range below 1 to 2 kHz and a high frequency range above approximately 1 to 2 kHz. Only the low frequency parts are processed binaurally and transmitted to the other side in each instance, since the high frequency parts can also be processed exclusively monaurally to a satisfactory degree. Once the respective parts have been processed binaurally or monaurally, they are then combined to form two monaural output signals SAL and SAR. 
     The advantage of this division of the signal to be processed is that a lower data rate is necessary both for the processing as well as for the transmission than in the case of a broadband transmission and/or processing. In the tangible example, only the low frequency signals below approximately 1 to 2 kHz have to be transmitted. 
     A further advantage of the binaural processing system consists in hardly any problems occurring with microphone noise in the case of low frequencies. The reason for this is that the microphone signals in the low frequency range are exchanged between the left and the right hearing device and a larger microphone distance, namely the distance from head to the other side, thus exists. This is particularly important especially for differential directional microphones. 
     Another advantage of the presented system consists in even smaller microphone distances than previously being possible for monaural processing of the high frequencies, since only higher frequency parts can be processed monaurally. The individual hearing devices can thus be of a more compact design if necessary.