How susceptibility to noise varies across speech frequencies

Abstract

It has been long assumed that the corrupting influence of noise on speech is uniform across all frequencies, and that the contribution of each speech frequency decreases at the same rate as noise is added. This assumption is evident in numerous previous works, and is seen clearly in the Speech Intelligibility Index where the contribution of each speech band is scaled in the same way according to the amount of noise present. Here, it is argued that susceptibility to noise may differ across speech bands. To test this hypothesis, the compound method [F. Apoux and E.W. Healy (2012) 132, J. Acoust. Soc. Am.] was modified to evaluate the noise susceptibility of individual critical bands of speech. Noise was added to each target speech band and the signal-to-noise ratio (SNR) required to reduce the contribution of that band by half was estimated. It was found that noise susceptibility varies greatly across speech bands, and that the SNR required to similarly affect each band differed by as much as 12 dB. Interestingly, no obvious systematic relationship appeared to exist between band importance and noise susceptibility.