Noise Suppression Method Based on Modulation Spectrum Analysis

Conventional methods for noise suppression can successfully reduce stationary noise. However, non-stationary noise such as intermittent and impulsive noise cannot be sufficiently suppressed since these methods do not focus on temporal features of noise. This paper proposes a method for suppressing both stationary and non-stationary noise based on modulation spectrum analysis. Modulation spectra (MS) of the stationary, intermittent, and impulsive noise were investigated by using the time/frequency/modulation analysis techniques to characterize the MS features. These features were then used to suppress the stationary and non-stationary noise components from the observed signals. Using the proposed method, the direct-current components of the MS in the stationary noise, harmonicity of the MS in the intermittent noise, and higher modulation-frequency components of the MS in the impulsive noise were removed. The following advantages of the proposed method were confirmed: (1) sound pressure level of the noise was dramatically reduced, (2) signal-to-noise ratio of the noisy speech was improved, and (3) loudness, sharpness, and roughness of the restored speech were enhanced. These results indicate that the stationary as well as non-stationary noise can be successfully suppressed using the proposed method.