Deborah A. Fantini
Dept. of Psychol., Essex Univ., Colchester CO4 3SQ, UK
Alan R. Palmer
MRC Inst. of Hear. Res., University Park, Nottingham NG7 2RD, UK
If one member of a series of equal-amplitude harmonics starts a few hundred milliseconds after the others, it may be ``enhanced'' and stand out perceptually. Viemeister and Bacon [J. Acoust. Soc. Am. 71, 1502--1507 (1982)] demonstrated that components produce more forward masking when enhanced than when present in a harmonic series without enhancement. Thus, enhancement appears to involve an increase in the internal level of a component. The present study was conducted to determine whether this result is also found in a loudness-matching task. Stimuli were derived from a harmonic series with a fundamental of 200 Hz. A 500-ms adaptor consisted of the series without the 1.8-, 2.0-, and 2.2-kHz components. A 100-ms standard included the 2-kHz component. Subjects heard the standard in the left ear followed by an identical 100-ms sound (the ``comparison'') in the right ear. They matched the loudness first of the background components and then of the 2-kHz component between the comparison and the standard. Preceding the standard by the adaptor reduced the loudness of the background components by 2 dB and raised the loudness of the 2-kHz component by 5 to 15 dB relative to the background components. Thus, loudness matching, like forward masking, demonstrates that enhancement increases the internal level of a component, but shows also that the levels of the background components are reduced.