Abstract:
The term roughness has been proposed to describe a sensation elicited by sinusoidal amplitude modulation (SAM) of pure tones and modulated wideband noise [E. Terhardt, Acustica 30, 201--213 (1974)]. Roughness of SAM tones is known to exhibit a close relationship to modulation depth. It is hypothesized that roughness of complex tones, as scaled against modulation depth of a SAM tone, can be predicted from the magnitude of the envelope spectrum. Subjects were asked to scale complex tones on the dimension of roughness by matching a test stimulus to a reference SAM tone of subjectively equivalent roughness. The test stimuli were drawn from complex tones consisting of a variable number of equal amplitude, harmonically related components. The reference set was 12 SAM tones with modulation depths spanning the range from detection threshold to 100 [Viemeister, J. Acoust. Soc. Am. 88, 1367--1373 (1990)]. The modulation frequency of the reference set varied across tests conditions according to the minimum component spacing of the tests stimulus. Results of the scaling experiments suggest roughness can be predicted as a function of the narrow-band peaks in the magnitude spectrum of the envelope. [Work supported by Ford Motor Company.]