| 摘要 |
The hearing aid has a microphone (1), analogue to digital converter or ADC (2), signal processing stage (4), digital-to-analogue converter or DAC (5), amplifier (6) and output transducer (7) in series in a signal path, an internal control path contg. a digital filter (9) with finite pulse response and adjustable transfer function and a measurement and control circuit (14) which determines the transfer function of an unwanted signal feedback path (6,7,8,1,2) from the output transducer and microphone and adjusts the filter coefficients to compensate the acoustic and/or mechanical feedback. The measurement and control circuit contains a pulse generator (10,11) for feeding short duration pulses into the feedback path and measures its transfer function from the triggered pulse response. The pulse duration is no greater than the inverse of the ADC and DAC sampling rate. |
