• Bruun, Erik
• Jørgensen, Ivan Harald Holger
• Pracný, Peter

Abstract

This paper deals with a system-level optimization of a back-end of audio signal processing chain for hearing-aids, including a sigma-delta modulator digital-to-analog converter (DAC) and a Class D power amplifier. Compared to other stateof-the-art designs dealing with sigma-delta modulator design for audio applications we take the maximum gain of the modulator noise transfer function (NTF) as a design parameter. By increasing the maximum NTF gain the cutoff frequency of modulator loop filter is increased which lowers the in-band quantization noise but also lowers the maximum stable amplitude (MSA). This work presents an optimal compromise between these. Increased maximum NTF gain combined with a multi bit quantizer in the modulator allows loweroversampling ratio (OSR) and results in considerable power savings while the audio quality is kept unchanged. The proposed optimization impacts the entire hearing-aid audio back-end system resulting in less hardware and power consumption in the interpolation filter, in the sigma-delta modulator and reduced switching rate of the<br/>Class D output stage.

Topics

• impedance spectroscopy
• laser emission spectroscopy