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's right ear and left ear, respectively, and which comprise means for stimulating the respective user'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's amplification system. The resulting improvements of signal level and SNR in the listener'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'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.