Frequency selectivity in amplitude-modulation detection

Abstract

For a broadband noise carrier, the modulation detection threshold for sinusoidal amplitude modulation (the test modulation) is measured in the presence of an additional modulation (the masker modulation). Two traditional approaches for revealing effects of frequency selectivity in the audiofrequency domain are shown to give comparable results in the modulation-frequency domain: (1) a typically peaked modulation-detection threshold pattern when the masker modulation is a fixed narrow band of noise, and (2) an effect of leveling off of the increase of the modulation-detection threshold when, for a fixed test-modulation frequency, the masker-modulation bandwidth is widened beyond a certain ‘‘critical’’ bandwidth. It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech-envelope spectrum or the modulation-transfer function in relation to speech intelligibility.