Patent Publication Number: US-8526648-B2

Title: System and method for providing hearing assistance to a user

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system and a method for providing hearing assistance to a user wherein audio signals from an audio signal source, which usually is a microphone arrangement, are transmitted by a transmission unit via a wireless audio link to a right ear unit and a left ear unit which are worn at or at least in part in the user&#39;s right ear and left ear, respectively, and which comprise means for stimulating the respective user&#39;s ear according to the transmitted audio signals. 
     2. Description of Related Art 
     Usually in such systems the wireless audio link is an FM (Frequency Modulation) radio link. The benefit of such systems is that sound captured by a remote microphone at the transmission unit can be presented at high sound pressure level to the hearing of the user wearing the ear units. In particular, the level of speech signals from the person using the transmission unit can be increased with regard to acoustic background noise. 
     A typical application of wireless audio systems the receiver unit is connected to or integrated into a hearing instrument, such as a hearing aid. The benefit of such systems is that the microphone of the hearing instrument can be supplemented or replaced by the remote microphone which produces audio signals which are transmitted wirelessly to the FM receiver and thus to the hearing instrument. In particular, FM systems have been standard equipment for children with hearing loss in educational settings for many years. Their merit lies in the fact that a microphone placed a few inches from the mouth of a person speaking receives speech at a much higher level than one placed several feet away. This increase in speech level corresponds to an increase in signal-to-noise ratio (SNR) due to the direct wireless connection to the listener&#39;s amplification system. The resulting improvements of signal level and SNR in the listener&#39;s ear are recognized as the primary benefits of FM radio systems, as hearing-impaired individuals are at a significant disadvantage when processing signals with a poor acoustical SNR. 
     Most FM systems in use today provide two or three different operating modes. The choices are to get the sound from: (1) the hearing instrument microphone alone, (2) the FM microphone alone, or (3) a combination of FM and hearing instrument microphones together. 
     Usually, most of the time the FM system is used in mode (3), i.e. the FM plus hearing instrument combination (often labeled “FM+M” or “FM+ENV” mode). This operating mode allows the listener to perceive the speaker&#39;s voice from the remote microphone with a good SNR while the integrated hearing instrument microphone allows to listener to also hear environmental sounds. This allows the user/listener to hear and monitor his own voice, as well as voices of other people or environmental noise, as long as the loudness balance between the FM signal and the signal coming from the hearing instrument microphone is properly adjusted. 
     An example of an FM system is found in Canadian 2 422 449 A1 wherein the FM receiver unit is mechanically connected to a hearing instrument. 
     Such FM systems often are used in rooms. However, due to reflections in rooms the quality of the reception of the FM audio signals will vary depending upon head movement, position of the user in the room, positions and movement of other people or objects, etc. This varying quality manifests itself by a kind of a hissing noise and is especially noticeable in very small FM receivers as these receivers are built with very small antennas. These “holes” in the FM audio signal reception quality are an issue both with the current analogue FM systems as well as with the upcoming new digital systems. 
     Further, binaural hearing systems are already available, wherein there is provided a usually wireless link between the right ear hearing aid and the left ear hearing aid for exchanging data and audio signals between the hearing aids for improving binaural perception of sound. Examples of such binaural systems can be found in European Patent Application 1 651 005 A2, U.S. Patent Application Publication 2004/0037442 A1 and U.S. Pat. No. 6,549,633 B1. In European Patent Application 1 531 650 A2 a binaural system is described wherein in addition to the binaural link a wireless audio link to a remote microphone is provided. A similar system is described in WO 02/074011 A2. 
     European Patent Application 1 657 958 A1 relates to a communication system comprising a plurality of hearing aids between which audio signals may be exchanged via wireless links. 
     U.S. Patent Application Publication 2005/0117764 A1 relates to a system comprising a right ear hearing aid and left ear hearing aid, each comprising a hearing coil for receiving audio signals from a telephone. The difference between the levels of the input signals of the two hearing devices at the hearing coils is measured and compared with a threshold value. If the difference in levels drops below or exceeds the threshold value, the respective hearing aid is switched to a telephone mode. 
     U.S. Patent Application Publication 2004/0252852 A1 relates to a binaural acoustic beam forming system comprising a right ear hearing aid and a left ear haring aid wherein the voice-to-background noise ratio of the audio signal captured by the microphone of the right ear hearing aid and the audio signal captured by the microphone of the left ear hearing aid is determined and compared and wherein these audio signals are mixed prior to being supplied to the respective loudspeaker of the hearing aids, with the mixing ratio depending on the noise power ratio, i.e. the ratio of the voice to background noise ratios of the left ear hearing aid and the right ear hearing aid, respectively. 
     SUMMARY OF THE INVENTION 
     It is a first object of the invention to provide for a hearing assistance system wherein audio signals from a remote audio signal source are provided wirelessly to both ears of the user and wherein the quality of the audio signal transmission should be optimized. 
     It is a second object of the invention to provide for a hearing assistance system wherein audio signals from a remote audio signal source are provided wirelessly to both ears of the user and wherein the system should be particularly economic. 
     According to the invention the first object is achieved by a system and a method according to the invention. This solution is beneficial in that, by detecting the quality of the right ear link and the left ear link and exchanging audio signals received from the transmission unit between the right ear unit and the left ear unit in order to select, as a function of the detected qualities of the right ear link and the left ear link, as input to the stimulating means the audio signal received by the respective receiver unit directly from the transmission unit, the audio signals received via the audio signal exchange between the right ear unit and the left ear unit and/or mixtures thereof, the quality of the audio signals transmitted from the transmission unit to any of the two ear units can be optimized, since a poor transmission quality of one of the audio links can be compensated by supplying the audio signal transmitted via the audio link having the better quality to both ear units via the audio signal exchange between the ear units. In particular, it is thereby made possible to always select the presently better one of the right ear audio link and the left ear audio link (i.e., the one having a higher degree of qualitative excellence) to be input to both the right ear unit and the left ear unit. 
     In some cases it may be sufficient to use a mixture of the audio signals received via the right ear audio link and the left ear audio link. If both audio links have sufficient quality, no exchange of audio signals between the right ear unit and the left ear unit is necessary. However, in this case it would be possible to use only one of the two audio links and to transmit the audio signals received via this link to the other ear unit, while the other one of the audio links is turned off in order to save power. 
     According to the invention, the second object is achieved by a system and a method as described herein and which is beneficial in that, by transmitting audio signals received from the transmission unit by one of the ear units to the other one of the ear units via a second wireless audio link, it is sufficient to equip only one of the ear units with a receiver unit for the audio signals transmitted from the transmission unit via the first wireless audio link, so that system complexity can be reduced in order to provide for a more economic system, while nevertheless the audio signals transmitted by the transmission unit can be provided at both ears of the user. 
     These and further objects, features and advantages of the present invention will become apparent from the following description when taken in connection with the accompanying drawings which, for purposes of illustration only, show several embodiments in accordance with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of the use of a hearing assistance system according the invention; 
         FIG. 2  is a block diagram of a first embodiment of a hearing assistance system according to the invention; and 
         FIG. 3  is a block diagram of a second embodiment of a hearing assistance system according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show a hearing assistance system comprising a transmission unit  10  comprising a directional microphone arrangement  12  consisting of two omnidirectional microphones M 1  and M 2  which are spaced apart, a right ear unit  14 R and a left ear unit  14 L, each comprising a receiver unit  16  and a hearing instrument  18 . The hearing instrument  18  comprises a loudspeaker  20 . The hearing instrument  18  and the receiver unit  16  may be connected by a mechanical/electrical interface  22  (for example, a so-called “audio shoe”), or they may be integrated into a common housing (as indicated by dashed lines in  FIG. 2 ). The hearing aid  18  could be of any type, for example, BTE (Behind-The-Ear), ITE (In-The-Ear) or CIC (Completely-In-the-Channel). The transmission unit  10  may be worn by a speaker  100  around his neck by a neck loop  24  acting as an antenna, with the microphone arrangement  12  capturing the sound waves  105  carrying the speaker&#39;s voice. The right ear unit  14 R is worn at or at least in part in the right ear  26 R of the user  101 , and the left ear unit  14 L is worn at or at least in part in the left ear  26 L of the user  101 . In addition to the voice  105  of the speaker  100  background/surrounding noise  106  may be present. 
     The transmission unit  10  comprises an audio signal processing unit  28  for processing the audio signals captured by the microphone arrangement  12  and a transmitter  30  for transmitting the processed audio signals via the antenna  24  via a left ear audio link  32 L to the receiver unit  16  of the left ear unit  14 L and via a right ear audio link  32 R to the receiver unit  16  of the right ear unit  14 R. 
     Each receiver unit  16  comprises an antenna  34 , a receiver  36  and an audio signal processing unit  38  for processing the audio signals received by the receiver  36  via the respective audio link  32 R,  32 L. Each hearing instrument  18  comprises a microphone arrangement  40  (which may comprises a single microphone or two spaced apart microphones) for capturing audio signals at the respective user&#39;s ear  26 R,  26 L, a central unit  42 , the loudspeaker  20 , a transceiver  44  and a corresponding antenna  46 . The transceiver  44  and the antenna  46  are provided for establishing a binaural link  48  between the hearing instruments  18  of the right ear unit  14 R and the left ear unit  14 L, respectively, which serves to exchange audio signals and control data/commands between the right ear unit  14 R and the left ear unit  14 L. In particular, the binaural link  48  serves to exchange audio signals received by the receiver units  16  of the right ear unit  14 R and the left ear unit  14 L, respectively. 
     The central unit  42  serves to process the audio signals received from the built-in microphone arrangement  40 , the audio signals supplied by the respective receiver unit  16  and the audio signals received by the transceiver  44  via the binaural link  48  from the hearing instrument  18  of the other one of the right ear unit  14 R and the left ear unit  14 L, respectively. The central unit  42  also serves to control the respective right ear unit  14 R and left ear unit  14 L. The processed audio signals are supplied from the central unit  42  to the speaker  20  for stimulating the respective ear  26 R,  26 L. 
     In each of the right ear unit  14 R and the left ear unit  14 L the quality of the respective right ear audio link  32 R and the left ear audio link  32 L is monitored. This can be done, for example, by a signal-to-noise-ratio (SNR) measurement of the signals received by the receiver unit  16 , by an RSSI (Received Signal Strength Indication) measurement (wherein the energy integral of the signal received by the receiver unit  16  is determined) or, if the links  32 R,  32 L are digital, by error-rate measurements. Such link quality monitoring may be carried-out in the receiver unit  16  (for example, by the audio signal processing unit  38 ) or in the hearing instrument  18  (for example, by the central unit  42  to which the signal received by the receiver unit  16  is supplied). If the link quality is monitored in the receiver unit  16 , the result of the analysis has to be supplied to the hearing instrument  18 , see dashed line in  FIG. 2 . 
     The result of the link quality monitoring is used for improving the quality of the audio signals transmitted by the transmission unit  10  in case that one of the right ear audio link  32 R and the left ear audio link  32 L has a significantly lower quality than the other one. To this end, in this case the audio signals received via one of the links  32 R,  32 L presently having the higher quality are transmitted via the binaural link  48  to the other one of the units  14 R,  14 L, and there they are used to replace or at least supplement the audio signals received by the receiver unit  16  of that unit  14 R,  14 L via that one of the links  32 R,  32 L presently having the lower quality, prior to being supplied as input to the respective loudspeaker  20 . Consequently, both the transmission/exchange of audio signals via the binaural link  48  and the selection of the audio signals to be supplied as input to the loudspeaker  20  are controlled according to result of the monitoring of the quality of the audio links  32 R,  32 L. 
     Practically, such control can be achieved by designing the system architecture such that one of the units  14 R,  14 L acts as a master and the other one acts as a slave, with the necessary information regarding the quality of the respective audio link  32 R,  32 L being exchanged/transmitted via the binaural link  48  from the slave to the master and with corresponding control commands being transmitted via the binaural link  48  from the master to the slave. 
     The selection of the audio signals which are supplied as input to the loudspeaker  20  is carried out by the central unit  42  of the hearing instrument  18  acting as the master; i.e. the decision is made by the central unit  42  of the master and corresponding control commands, if necessary, are transmitted via the binaural link  48  to the central unit  42  of the hearing instrument  18  of the other one of the units  14 R,  14 L. 
     According to a preferred embodiment the binaural link  48  is established once the quality of at least one of the units  32 R,  32 L has been found to be below a pre-set threshold value, and the audio signals received via the better one of the links  32 R,  32 L is supplied via the binaural link  48  to that one of the units  14 R,  14 L having the worse link  32 R,  32 L where these audio signals are used to replace or at least supplement the audio signals received via the worse one of the links  32 R,  32 L. 
     According to a modified embodiment it would be possible to turn-off the worse one of the links  32 R,  32 L as long as the better one of the links  32 R,  32 L has a quality above the pre-set threshold value in order to save power in the respective receiver unit  16 . 
     Preferably the audio links  32 R,  32 L are radio frequency links, such as an analog FM link. However, according to an alternative embodiment the links  32 R,  32 L may be digital audio links. The binaural link  48  preferably is a digital link, for example, a FSK (Frequency-Shift-Keying) modulated link. 
     An alternative embodiment of the invention is shown in  FIG. 3 , wherein only one of the ear units (for example, the left ear unit  14 L) is provided with a receiver unit  16  for the audio link  32 L from the transmission unit  10 , whereas the other one of the ear units (in the example of  FIG. 3  the right ear unit  114 R) does not comprise a receiver unit for the audio signals transmitted from the transmission unit  10 , so that the right ear unit  114 R comprises only a hearing instrument  18 . According to this embodiment, the audio signals received by the left ear unit  14 L via the audio link  32 L from the transmission unit  10  are permanently supplied via the binaural link  48  to the hearing instrument  18  of the right ear unit  114 R in order to supply the audio signals transmitted by the transmission unit  10  via the link  32 L and the binaural link  48  to the loudspeaker  20  of the right ear unit  114 R. Thereby for binaural hearing instruments  18  capable of establishing a binaural link  48  the need for a second receiver unit  16  for receiving audio signals directly from the transmission unit  10  is eliminated, whereby system complexity is reduced. 
     Depending on the type of the hearing instrument  18 , the output if the receiver unit  16  may be connected to a separate high impedance audio input of the hearing instrument  18 , as shown in  FIGS. 2 and 3 , or it may connected to a low impedance audio input of the hearing instrument  18  which is connected in parallel to the microphone  40  (see dashed lines in  FIGS. 2 and 3 ). 
     While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modifications as encompassed by the scope of the appended claims.