Note on measures for spectral flatness

Spectral flatness is a feature of acoustic signals that has been useful in many audio signal processing applications. The traditional definition of spectral flatness is the ratio of the geometric mean to the arithmetic mean of the magnitude spectrum of the signal, as obtained from the DFT. Presented is an analysis of this measure and the shortcomings. To overcome these shortcomings, a robust measure based on the concept of entropy is proposed. Although this entropy-based measure is derived from a completely different standpoint, it is closely related to the traditional measure, the relation of which is also derived here. Given the importance that spectral flatness is gaining in the field of audio signal processing, it is believed that an understanding of this measure and the development of a robust version as proposed is exigent.