SUITAB LE FOR EXTENSIVE SUBBAND- SIGNAL AMPLIFICATION

Overs amp ling, complex-modulate d digital subband coder filter banks are commonly adopted in modern hearing aids to allow for individual amplification of subband signals in order to compensate for hearing losses of impaired persons. Minimum power consump­ tion and low group delay have been the main concern in the design of these filter banks. Guaranteeing frequency-indepe ndent and low group delay in case of subband-signa l amplification has, however, been neglected in the past. In this contribution, we investigate the delay and amplification properties of oversampling complex-modulate d FIRfilter banks in case of extensive subband signal amplification. Based on these re­ sults. a sufficient condition for constant group delay is derived. Fur­ thermore. we present a compensation method which allows for con­ stant group delay, even if the sufficient condition is violated. An illustrative design example demonstrates the potential of the com­ pensation method.