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Effect of a noise modulation masker on the detection of second-order amplitude modulation

Lookup NU author(s): Rebecca Millman, Dr Gary Green, Professor Adrian ReesORCiD


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Amplitude modulation waveforms can contain complex patterns of modulation frequency and depth that are characteristic of many biologically relevant sounds. To investigate the mechanisms involved in the processing of such patterns, we measured detection thresholds for second-order amplitude modulation (AM), a sinusoidal AM in which AM depth varies with time at frequency fm′. Second-order AM generates sidebands in the modulation spectrum on either side of the frequency components introduced by the first-order AM. Previous masking studies suggested that a distortion product located at fm′ contributes to the detection of second-order AM. This hypothesis was tested by masking the putative distortion product using a noise modulation masker centred on (1) the second-order modulation frequency (fm′=2 Hz) and (2) the first-order modulation frequency (fm=16 Hz). The second-order AM was applied to a 5-kHz pure-tone carrier. Increasing the depth of a 2-Hz-wide noise modulator masker centred on 2 Hz had little effect on detection thresholds for second-order AM, but increased detection thresholds for 2-Hz first-order AM six-fold. Increasing the depth of an 8-Hz-wide noise modulator masker centred on 16 Hz increased detection thresholds for both first- and second-order AM three-fold. These results show that the detection of the second-order AM, when fm′ is 2 Hz, is not dependent on the detection of modulation at fm′ but is dependent on the detection of modulation components centred on fm. © 2003 Elsevier Science B.V. All rights reserved.

Publication metadata

Author(s): Millman RE, Green GGR, Lorenzi C, Rees A

Publication type: Article

Publication status: Published

Journal: Hearing Research

Year: 2003

Volume: 178

Issue: 1-2

Pages: 1-11

ISSN (print): 0378-5955

ISSN (electronic): 1878-5891

Publisher: Elsevier BV


DOI: 10.1016/S0378-5955(02)00795-5

PubMed id: 12684172


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