| 摘要 |
A hearing aid in which the sound reception characteristics are selectable by a user to provide non-directional or directional reception, as desired. The hearing aid employs a differential transducer having two sound receiving ports and operative to convert sound information into an electrical output and to which sound energy can be directed in one of two modes. In one mode of operation, for providing non-directional reception, sound is received from a front aperture of the hearing aid and directed to first and second input ports of the transducer, the sound being directed to the second port via an acoustic filter. In a second mode of operation, for providing directional reception, the second input port of the transducer is coupled to a rear aperture of the hearing aid and the first input port remains coupled to the front aperture. Sound energy received from the rear of the hearing aid is substantially minimized by action of the transducer without affecting energy from the front of the hearing aid. The acoustic filter in the second transducer port path during non-directional operation is used to match the frequency and phase characteristics of the non-directional mode response to the frequency and phase characteristics of the directional mode frontal response so that switching from one mode to another does not materially alter the quality of sound reception from the front direction of the hearing aid.
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