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

Abstract

Abstract-A low power digital signal processor (DSP) for a digital hearing aid chip is presented. The DSP integrates three programmable digital finite impulse response (FIR) filters. Each FIR filter can have one pass-frequency out of seven preset frequencies so that only three FIR filters can have the same flexibility as seven filters. Additionally, a silence mode is defined in which only one filter is activated. A digital voice activity detection circuit is implemented for this purpose. The DSP is implemented as part of a fully integrated digital hearing aid chip. It uses a 0.18 µm CMOS process and occupies an area of 0.5 mm 2 . Power consumption is 25 µW in normal operating mode and 9 µW in silence mode at 0.9-V supply.

Three-channel variable filter-bank for digital hearing aids

“…5 illustrate the matching result and matching errors, respectively. The maximum error is 1.32 dB, while that in [1] is about 4 dB. Therefore, the matching accuracy here is much higher than that in [1].…”

“…The prototype filter is the second-order Chebyshev type-I analog lowpass filter [Audiogram]: Fig. 3 shows an audiogram used in [1], which has mild hearing loss in high frequencies and is called ski slope loss. Fig.…”

“…Therefore, it is desirable to design a filter-bank with simple structure but high fitting accuracy for various audiograms. In [1], eight bandpass FIR filters are pre-designed and stored, and three out of the 8 FIR filters are selected and used to match a given audiogram. In [2], an FIR filter-bank with 7 subfilters is designed, and the order of each subfilter is 22.…”

A Reconfigurable Sound Wave Decomposition Filterbank for Hearing Aids Based on Nonlinear Transformation

“…Here "reconfigurable" means that different subbands distributions could be obtained according to the control parameters without changing the filterbank's structure. In [15], a low power digital signal processor for a digital hearing aid chip was proposed, in which a 3-band filterbank was constituted with three programmable digital FIR filters. Each FIR filter had seven available pass-frequencies, so the filterbank had the same flexibility as seven filters.…”