Subject: Pitch and forward masking From: "Brian C. J. Moore" <bcjm(at)CUS.CAM.AC.UK> Date: Fri, 16 Jan 2004 10:17:48 +0000 X-Cam-ScannerInfo:http://www.cam.ac.uk/cs/email/scanner/Dear List members, In response to the recent email from Chen-Gia Tsai, I wrote to him to ask: >Why do you think that the pitch strength of a sound (a complex tone in this >case) should influence its effectiveness as a forward masker of a sinusoid? He replied: "Thank you very much for your email. There are two assumptions in my hypothesis. First, the grouping rule of harmonicity is modified as that components at nf0 are grouped only when the pitch sensation of f0 is robust. In the other words, if the pitch strength of f0 is low, components at nf0 will not be grouped despite harmonicity. This assumption appears to be supported by my model of the perception of roughness induced by subharmonics. Second, well-grouped components tend to be segregated from other tones. Effectiveness of masking is influenced by the grouping mechanism integrating information across auditory channels. This assumption appears to be supported by the effect of comodulation masking release." With regard to the first assumption, it should be noted that the harmonics in the study of Gockel et al. were all unresolved. Regardless of the relative phases of the components, the maskers were heard as strongly fused single sounds. With regard to the second assumption, forward masking can be influenced by across-channel mechanisms when there is a possibility of "confusion" of the signal with the masker. See, for example, Moore, B. C. J., 1980. Detection cues in forward masking. In: van den Brink, G., Bilson, F. A. (Eds.), Psychophysical, Physiological and Behavioural Studies in Hearing, Delft University Press, Delft, pp. 222-229. Moore, B. C. J., Glasberg, B. R., 1982. Contralateral and ipsilateral cueing in forward masking. J. Acoust. Soc. Am. 71, 942-945. However, this occurs mainly when the masker is a narrowband sound of the same centre frequency as the sinusoidal signal. "Confusion" effects do not occur when the masker is a broadband sound and the signal is a sinsusoid, as was the case in the study of Gockel et al. Gockel, H., Moore, B. C. J., Patterson, R. D., 2003. Louder sounds can produce less forward masking: Effects of component phase in complex tones. J. Acoust. Soc. Am. 114, 978-990. So, I don't think that Chen-Gia Tsai's alternative "explanation" of the results of Gockel et al. can be correct. Best wishes, Brian Brian C.J. Moore, Ph.D, FMedSci, FRS Professor of Auditory Perception, Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, England tel. + 44 (0) 1223 333574 fax + 44 (0) 1223 333564 http://hearing.psychol.cam.ac.uk/