| Abstrakt: |
Previous research in this laboratory on the pitch of unresolved, two-component complex tones (UTCC) indicated that these complexes may have an asymmetric representation in the auditory periphery. These signals are composed of two sinusoidal components separated in frequency by a small ΔF, and in amplitude by a small ΔI. While the long-term spectra of these signals do not vary with time, they have short-term periodic variations in both amplitude (envelope) and frequency. For one member of a UTCC pair at a given ΔF, the lower frequency component is more intense than the higher frequency one; for the complementary signal the amplitude relationship is reversed. When the lower component is more intense, the pitch of the complex is slightly lower than the pitch for the signal with a stronger higher component. Pitch matches to these complementary signals reveal asymmetries that are not evident in the calculation of the short-term frequency fluctuations of each signal. This study was designed to determine the masking patterns for complementary two-component complex tones using a simultaneous masking procedure similar to Ronken's [J. Acoust. Soc. Am. 54, 905-915 (1973)]. Each two-component signal was used as a masker, in turn. The brief (10-ms) probe was fixed in level and occurred at selected times throughout the course of the 300-ms masker. The adaptive procedure of Levitt [J. Acoust. Soc. Am. 49, 467-477 (1971)] was used to adjust the probe frequency. Masker complexes were centered at 1000 Hz, and ΔF ranged from 5 to 100 Hz. All subjects tested had normal hearing and were well practiced in the task. Results should help to determine whether asymmetric excitation patterns contribute to the asymmetric pitch matches to symmetrically spaced complex signals. [Research supported by grants from NINCDS.] [ABSTRACT FROM AUTHOR] |
