Continuous-time audio noise suppression and real-time implementation

In this paper, we propose a continuous-time audio noise suppression algorithm for reducing stationary background noise in a single microphone signal. The algorithm is targeted for implementation in sub-threshold analog floating-gate transistor circuits for extremely low-power systems. The noise suppression algorithm divides the noisy signal into exponentially spaced sub-bands and estimates the noisy signal envelope and the noise envelope to calculate a time-varying gain for each sub-band based on each band´s a posteriori SNR. A sigmoidal gain function in for use in the analog system is introduced and a normalized SNR is also proposed for consistent noise suppression for different input noise variances. Simulations of the system show promising results.