A flexible filterbank structure for extensive signal manipulations in digital hearing aids

A Low Power Digital Signal Processor with Adaptive Band Activation for Digital Hearing Aid Chip

“…Recently up to sixteen filters [3] have been used in an effort to achieve a high level of flexibility. Increasing the number of filters enhances the likelihood for a better fitting, but such an implementation would not only require a large amount of processing power, since the audiograms of most patients suffering from hearing loss have nearly monotonic curves [5], a lot of power would be wasted.…”

“…While this approach is simple and power efficient, it is only applicable to patients with specifically shaped audiograms and thus has limited flexibility. A more elaborate approach is to divide the frequency spectrum into many bands [3] [4]. Recent works have used up to 16 bands.…”

Affine projection algorithm for oversampled subband adaptive filters

“…On the other hand, in many adaptive applications, OverSampled Subband Adaptive Filters (OS-SAFs) have become a common practical solution [4][5] because of the well-known advantages of subband processing, simplified implementation and much reduced distortion (aliasing) as compared to critical sampling implementations [6]. OS-SAF offers a simplified structure that significantly reduces the aliasing level in subbands.…”

“…OS-SAF offers a simplified structure that significantly reduces the aliasing level in subbands. In order to reduce group delay while maintaining aliasing at a low level, it is desirable to use an over-sampling factor (OS) of 2 or more [5].…”

“…1 shows the block diagram of the OS-SAF system in the noise cancellation setup. Due to its desirable properties, a very efficient Weighted OverLap-Add (WOLA) filterbank [5] is employed as the analysis/synthesis filterbank in our research. The WOLA is a highly over-sampled, generalized DFT, uniform filterbank (OS = 2, 4 or more).…”