Title: Spatial release from masking for amplitude modulated and non-modulated noise stimuli
Authors: Norbert Kopčo, Barbara Shinn-Cunningham
The ability to hear a target sound (T) masked by another sound (M) improves when the T and M are spatially separated, a phenomenon known as �spatial release from masking� (SRM). Target detectability is also influenced by temporal characteristics of T and M (e.g., by the presence or absence of amplitude modulation). The current study examines how SRM is influenced by amplitude modulation.
Detection thresholds were measured for a broadband noise target (T) temporally and spectrally centered within a broadband noise masker (M). Thresholds were measured for all combinations of five spatial configurations of T and M and five modulation conditions (all combinations of T and M modulated and unmodulated; when both T and M were modulated, the modulation could either be equal or pi out of phase). In all cases, the amplitude modulation, if present, had a rate of 40 Hz and depth of 0.5.
Modulation had a complex effect on detection threshold. Thresholds improved by as much as 6 dB (relative to the no-modulation control) in some spatial configurations, but were nearly unaffected in others. These results have important implications for understanding the processes involved in the perception of simultaneous complex signals.
[Work supported by NSF and NAS]