A hearing aid for a person with asymmetric hearing perception (a weaker ear system and a better ear system) employs conventional frequency-selective amplification (26L) of sound coming to the weaker ear's system and frequency selective amplitude attenuation (32) and arrival time adjustment (retardation or relative advancement) (34) of sound coming to the better ear's system so that its resultant characteristics match those of the weaker ear's system, as aided, or even without aiding the weaker ear's system. As a result, sound perceived by both ear systems is matched or balanced, at each frequency, in both arrival time and amplitude. Such interaural balancing effects a great improvement in the binaural processing mechanism, which in turn increases speech perception, especially in the presence of general noise or adjacent localized noise sources. The aid may be implemented by a pair of microphones (24L, 24R), one for each ear's system. The signal from the microphone to the weaker ear's system includes a conventional variable gain amplifier (26L) and a conventional frequency selective filter (12) to provide tailored amplification of the sound to the weaker ear's system, insofar as possible. Also the channel to the weaker ear's system includes a fixed delay (28) to compensate for a delay in the channel to the better ear's system. The signal from the microphone to the better ear's system includes a variable gain amplifier (26R) and a set of bandpass filters (30) to cover the audio spectrum in discrete steps. Each filter is connected in series with a selected attenuator (32) and a selected time delay (34) so as to match the perceived arrival time and amplitude level at its band with that of the weaker ear's system. The components may be provided in three housings, one for each ear's system (36R, 36L) and a common control unit (38), or in two ear's system housings (Fig. 4A) connected by radio signals or by wiring (58), which can be external or which may run through the frame of eyeglasses (60). The arrival time and attenuation adjustments can alternatively be provided by a passive in-the-ear acoustic filter (76).
PARADOXICAL HEARING AID