In the context of this application, a hearing instrument is to be understood as a tiny, electronic device configured for being placed behind or in an ear of a person having an identified hearing loss, i.e. a person having difficulty perceiving certain sounds in his or her environment. The extent and character of the hearing loss is routinely determined by a professional audiologist, or hearing instrument fitter, by recording a sensory audiogram of the person's hearing ability at a range of different frequencies and subsequently selecting and programming a hearing instrument in such a way that the hearing loss of the person is compensated or alleviated, e.g. by amplifying certain frequency ranges in the hearing instrument where the person has difficulty perceiving sounds. In this context, the recorded audiogram and corresponding compensation programmed into the hearing instrument is denoted a hearing loss correction prescription.
Spectacles are also usually fitted by professional optometrists in order to correct vision deficiencies such as astigmatism and other accommodation problems. Apart from spectacles, corrective means may also include contact lenses and recently photorefractive keratectomy, or laser eye surgery. Since both vision problems and hearing deficiencies have a strong tendency to develop with age, and the life expectancy of the population is increasing, many elderly people in modern society suffer from identified problems with both hearing and seeing, and may therefore need to use both a pair of prescription spectacles and one or two hearing instruments simultaneously.
Behind-the-ear (BTE) hearing instruments are notoriously difficult to use with a pair of spectacles due to the fact that the spectacle side bars of the pair of spectacles get entangled with the hearing instruments during use. Therefore, hearing instruments of the in-the-ear (ITE) or the in-the-canal (ITC) type are preferably used together with a pair of spectacles instead of BTE hearing instruments. However, ITE hearing instruments have inferior sound directionality in comparison with BTE hearing instruments due to space constraints in the ITE hearing instrument, limiting the effect of directional microphones in ITE hearing instruments. Directionality, i.e. the capability of enhancing sounds from a particular direction, in hearing instruments is usually obtained by utilizing two or more microphones in a directional microphone array which, together with suitable filtering, favors acoustic signals from a particular direction, usually the direction the hearing instrument user is facing at any given time. ITE hearing instruments having directional microphones do exist, but the short distance between the microphones in a directional microphone pair in an ITE hearing instrument severely limits the hearing instruments' ability to discriminate sounds originating from other directions than the front direction in favor of sound from the frontal direction. As a consequence, hearing instrument users wearing spectacles are therefore unable to benefit fully from the improved directionality offered by BTE hearing instruments.
Wireless, external microphones for use with hearing instruments are known. Various types of external microphones exist, including hand-held, table-top and clip-on types. It would be beneficial to use such a wireless microphone in conjunction with a pair of spectacles. However, an unobtrusive way of positioning one or more wireless microphones on or in a pair of spectacles does not yet exist.
Contemporary hearing instruments comprise wireless transceivers for communicating bidirectionally with e.g. external microphones, remote controllers, personal sound systems or other hearing instruments. A preferred transceiver system exploits the 2.4 GHz frequency band for wireless communication with the hearing instruments. The wireless communication may comprise remote control commands, digital audio streams, prescription fitting telegrams, service readouts, signal processing coordination parameters and synchronization impulses.
In the context of this application, a transceiver is to be understood as an electronic device capable of transmitting and receiving radio signals. Such a radio device may be embodied as an off-the-shelf unit or as part of the integrated circuit providing the functionality of the hearing instrument, i.e. amplification, compression, hearing loss compensation etc. A preferred transceiver for use with a hearing instrument may be configured to operate as both a transmitter and a receiver, solely as a transmitter or solely as a receiver, according to the desired purpose of the transceiver. If e.g. a remote microphone unit is used with a hearing instrument, the transceiver in the microphone unit may preferably be configured only to transmit wireless radio signals, and the transceiver in the hearing instrument may be configured only to receive wireless radio signals, even though both the microphone unit transceiver and the hearing instrument transceiver may actually be realized by identical circuits configured differently. Thanks to the small physical size of the transceiver, it may easily fit into a hearing instrument.
Wireless synchronization signals transmitted from one hearing instrument to another have to be powerful enough to be perceived by a hearing instrument on the opposite side of the head of the hearing instrument user due to the fact that the user's head acts as an obstacle to the transmitted signals. The power requirement of the hearing instrument transceiver while transmitting wireless signals to another hearing instrument therefore puts a heavy load on the hearing instrument battery which, for space considerations, has to be physically small in order to fit inside an ITE-type hearing instrument. A need thus exists to facilitate wireless communication between two hearing instruments in a way which is less demanding on the battery.
Spectacle-wearing hearing instrument users are often having trouble using BTE-type hearing instruments due to the fact that the hearing instruments themselves become entangled with the side bars of the pair of spectacles with e.g. the risk of the hearing instrument falling off the pinna of the hearing instrument user as a result. Glasses with built-in hearing instruments, so-called hearing spectacles, have existed for a long time but are of limited use if the hearing instrument user does not need to wear glasses all the time, e.g. if the hearing instrument user only requires glasses for reading. In this case, a hearing instrument user may have to settle for a pair of ITE hearing instruments. However, ITE hearing instruments inherently provide limited directional sound information to the hearing instrument user due to the limited maximal possible distance between the microphones because of the small dimensions of the outer shell of the ITE hearing instrument. The smaller dimensions of an ITE hearing instrument also incurs a restriction to the physical size and power capability of the hearing instrument battery, thus making e.g. wireless communication between a pair of binaural hearing instruments difficult or even impossible. It would therefore be beneficial to provide an ITE-type hearing instrument user wearing glasses regularly with hearing instrument features associated with BTE-type hearing instruments, such as good microphone directivity and wireless exchange of information between hearing instruments. It would be a further advantage if these features were provided without having to make any significant changes to a pair of existing ITE hearing instruments.