Discrimination between harmonic tone complexes and bandpass noise signals presented within lowpass noise

Abstract

Threshold levels were measured at which harmonic tone complex targets could be discriminated from bandpass noise targets both presented within a diotic 2-kHz lowpass filtered noise masker with 65 dB SPL. In the 3IFC paradigm, one interval contained a sine-phase tone complex (20-Hz spacing) while the remaining intervals contained a bandpass noise with the same bandwidth, center frequency (1 kHz) and overall level as the tone complex. In addition, detection thresholds were measured for both targets using the same masker. When interaurally in-phase targets with a 100-Hz bandwidth were used, discrimination thresholds were about 8 dB higher than the detection thresholds. When out-of-phase targets were used, the difference between discrimination and detection thresholds was 18 dB, which was mainly due to a decrease of about 15 dB of the detection thresholds (BMLD). For 1500-Hz wide targets, the discrimination and detection thresholds were more similar. For the in-phase condition, the discrimination and detection threshold overlapped while for the out-of-phase conditions, discrimination thresholds exceeded the detection thresholds by only 5 dB. Assuming that discrimination is based on the processing of the temporal structure of the targets, this processing seems to be more efficient for wide- than for narrow-band targets.