Observer weighting of interaural cues in positive and negative envelope slopes of amplitude-modulated waveforms

Abstract

The auditory system can encode interaural delays in highpass-filtered complex sounds by phase locking to their slowly modulating envelopes. Spectrotemporal analysis of interaurally time delayed highpass waveforms reveals the presence of a concomitant interaural level cue. The current study systematically investigated the contribution of time and concomitant level cues carried by positive and negative envelope slopes of a modified sinusoidally amplitude-modulated (SAM) high-frequency carrier. The waveforms were generated from concatenation of individual modulation cycles whose envelope peaks were extended by the desired interaural delay, allowing independent control of delays in the positive and negative modulation slopes. In experiment 1, thresholds were measured using a 2-interval forced-choice adaptive task for interaural delays in either the positive or negative modulation slopes. In a control condition, thresholds were measured for a standard SAM tone. In experiment 2, decision weights were estimated using a multiple-observation correlational method in a single-interval forced-choice task for interaural delays carried simultaneously by the positive, and independently, negative slopes of the modulation envelope. In experiment 3, decision weights were measured for groups of 3 modulation cycles at the start, middle, and end of the waveform to determine the influence of onset dominance or recency effects. Results were consistent across experiments: Thresholds were equal for the positive and negative modulation slopes. Decision weights were positive and equal for the time cue in the positive and negative envelope slopes. Weights were also larger for modulations cycles near the waveform onset. Weights estimated for the concomitant interaural level cue were positive for the positive envelope slope and negative for the negative slope, consistent with exclusive use of time cues.

The rhythm of attention: Perceptual modulation via rhythmic entrainment is lowpass and attention mediated

“…Finally, while it is not unusual for auditory experiments to employ three subjects per condition (Hsieh, Petrosyan, Goncalves, Hickok, & Saberi, 2011;Hsieh & Saberi, 2010), and while several statistical tests converge in support of the main conclusions of this experiment, one should nonetheless exercise some caution in interpreting these results due to the comparatively smaller number of subjects. Specific support, however, for a relatively robust effect includes (1) a statistically significant difference between fixed-level and randomlevel conditions; (2) an absence of an effect, as predicted, in the fixed-level condition that was additionally supported by Bayes factor analysis; and (3) completion of over 16,000 trials by the three subjects in a within-subject's design, which, even for psychophysical experiments, is a relatively large number.…”

Imperfect pitch: Gabor’s uncertainty principle and the pitch of extremely brief sounds

“…To determine the accuracy with which a model of the auditory periphery can predict pitch-discrimination performance for the stimuli used in our study, we examined the output of an autocorrelation model with several frontend preprocessing stages. The model consisted of a bank of 30 fourthorder GammaTone bandpass filters spaced logarithmically from 50 to 3000 Hz (Holdsworth et al, 1988;Saberi, 2007, 2009;Hsieh et al, 2010Hsieh et al, , 2011Saberi and Petrosyan, 2005). Filter bandwidths were based on human auditory filter estimates measured in notched-noise (Glasberg and Moore, 1990).…”