Ultra Low-Power ANSI S1.11 Filter Bank for Digital Hearing Aids

• Main Authors: Yueh-Tai Li, 李岳泰
• Other Authors: Chih-Wei Liu
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/43937119586307946972

碩士 === 國立交通大學 === 電子工程系所 === 97 === Most advanced hearing aids contain a filter bank to decompose the input signal into different frequency bands so that the properly prescribed gains can be applied on those bands to compensate the hearing loss. The ANSI S1.11 1/3-octave filter bank is preferred for hearing aid applications because it well matches the human hearing characteristics. However, most existing filter banks for hearing aids implement proprietary filter banks that are not compliant with the ANSI S1.11 1/3-octave specifications because of the high computational complexity. On the other hand, those existing ANSI S1.1 designs do not target at the power-critical applications, such as hearing aids, so they are not suitable for hearings. Besides, they are all based on IIR filters, which may suffer from the round-off noise and stability issue after quantization. Hence, this thesis presents a low-power FIR-based design of the ANSI S1.11 1/3-octave filter bank, of which the power consumption is minimized through algorithmic, numerical and architectural optimization. The proposed filter bank adopts a multirate architecture to reduce data rates on the bandwidth-limited bands. A systematic coefficient design flow is also proposed to minimize the filter order thereof. In an 18-band digit hearing aid with 24 KHz sampling rate, the proposed design need only 4% multiplications and additions of a straightforward FIR filter bank implementation. The proposed filter bank has been implemented using the cell-based design flow with the Artisan Metro cell library in the TSMC 0.13μm CMOS technology. The simulation result shows this design consumes 77.33μW for 24 KHz and 18-band audio signal processing. Compared with other filter bank designs, the proposed one saves 46% ~ 80% power dissipation.