A Continuous-time Speech Enhancement Front-end for Microphone Inputs

In this paper, we present a real–time noise suppression system implemented with analog VLSI. The algorithm implemented is designed to reduce stationary background noise in single– microphone signals while preserving the non–stationary signal component. Because the system relies on analog computation rather than digital, it has benefits such as extremely low power consumption and real-time computation. The algorithm is based on an adaptive Wiener filter algorithm, adapted to take advantage of analog processing capabilities provided by floating-gate analog VLSI circuits. Noise suppression processing is performed on continuous-time signals in one-third octave subbands. The analog components described as parts of this system include a C second–order section band-pass filter, peak and minimum detectors, a translinear division circuit, and a differential multiplier. Floating–gate circuits are used to set bias points and adjust offsets.