Using Spectral Subtraction for Suppression of Noise in Speech Signals with Analog Integrated Circuits

A new modification of the spectral subtraction algorithm is presented which enables operating entirely in the time domain and is thus suitable for realization in analog integrated circuits. The noise spectrum is obtained during speechless intervals and stored for spectral subtraction when speech is present in the signal. The frequency range of interest of the speech signal is divided into narrow frequency bands by means of a bank of band-pass filters. For each frequency band the noise model is realized as an auxiliary signal multiplied by a particular weight. A subsystem is presented that produces an output signal whose power is equal to the difference between the input signal power and the noise model power for each frequency channel, thereby realizing the spectral subtraction. Circuits to achieve the described operation are outlined. Finally, simulation results of the noise removal algorithm are shown in the form of a spectrogram and the results showing improvement in automatic speech recognition are given.