Effect of masker harmonicity on informational masking.

Detection thresholds for a tone in an unfamiliar tonal pattern can be greatly elevated under conditions of masker uncertainty [Neff and Green, Percept. Psychophys. 41, 409-415 (1987); Oh and Lutfi, J. Acoust. Soc. Am. 101, 3148 (1997)]. The present experiment was undertaken to determine whether harmonicity of masker tones can reduce the detrimental effect of masker uncertainty. Inharmonic maskers were comprised of m=2-49 frequency components selected at random on each presentation within 100-10000 Hz, excluding frequencies between 920-1080. Harmonic maskers were comprised of frequency components selected at random within this same range, but constrained to have a fundamental frequency of 200 Hz. For inharmonic maskers the signal was a 1000-Hz tone. For harmonic-maskers the signal was a tone whose frequency was either harmonically (1000 Hz) or inharmonically (1047 Hz) related to the masker. In all conditions the amount of masking was greatest for m = 20-40 components. At this point, harmonic maskers with harmonic signal produced an average of 9-12 dB less masking than inharmonic maskers. Harmonic maskers with inharmonic signal produced an average of 16-20 dB less masking.