Index of content:
Volume 119, Issue 2, February 2006
- PSYCHOLOGICAL ACOUSTICS 
119(2006); http://dx.doi.org/10.1121/1.2159430View Description Hide Description
Induced loudness reduction (ILR) is the decline in the loudness of a weaker tone induced by a preceding stronger tone. In this study we investigate how ILR depends on exposure time and signal frequency. For 12 listeners, successive magnitude estimation was used to measure the loudness of 70-dB-SPL test tones, presented with and without preceding 80-dB-SPL inducer tones at the same frequency. Experiment 1 measured the evolution of ILR over time at . The results suggest that ILR may begin after a single inducer presentation, and increases over at least 2 to as the inducer and test tones are repeated every few seconds. Following the cessation of the inducer, the recovery of loudness is slow and still incomplete after . Experiment 2 extended the measurements to additional signal frequencies. The results show that the amount of ILR and its evolution over time are approximately the same at frequencies from 0.5 to . Similarly, loudness matching showed no effect of frequency on ILR, which averaged . These findings, together with previously noted similarities among ILR, ipsilaterally induced loudness adaptation, and temporary loudness shift, indicate that loudness reduction induced by stronger sounds is a very common phenomenon.
119(2006); http://dx.doi.org/10.1121/1.2151788View Description Hide Description
This study investigated comodulation detection differences (CDD) for fixed- and roved-frequency maskers. The objective was to determine whether CDD could be accounted for better in terms of energetic masking or in terms of perceptual fusion/segregation related to comodulation. Roved-frequency maskers were used in order to minimize the role of energetic masking, allowing possible effects related to perceptual fusion/segregation to be revealed. The signals and maskers were composed of -wide noise bands. The signal was either comodulated with the masker (A/A condition) or had a temporal envelope that was independent (A/B condition). The masker was either gated synchronously with the signal or had a leading temporal fringe of . In the fixed-frequency masker conditions, listeners with low A/A thresholds showed little masking release due to masker temporal fringe and had CDDs that could be accounted for by energetic masking. Listeners with higher A/A thresholds in the fixed-frequency masker conditions showed relatively large CDDs and large masking release due to a masker temporal fringe. The CDDs of these listeners may have arisen, at least in part, from processes related to perceptual segregation. Some listeners in the roved masker conditions also had large CDDs that appeared to be related to perceptual segregation.
119(2006); http://dx.doi.org/10.1121/1.2159429View Description Hide Description
Minimum resolvable angles (MRAs) for sound localization in azimuth in the gerbil were determined in a behavioral study using tones, 300-Hz bands of noise centered at frequencies between and and broad-band noise of on average SPL overall level. Using the method of constant stimuli, seven gerbils were trained in a two-alternative-forced-choice procedure to indicate if sounds were presented to them from the left or from the right by choosing the left or right arm of a Y-shaped cage. The MRA is the minimum angle between two loudspeaker locations that the gerbils discriminated. Animals were either stimulated from the front or from the back . The MRA for broad-band noise randomly varying in level by was and for gerbils stimulated from the front or back, respectively. Generally a gerbil’s MRA for tones declined up to reaching and for gerbils stimulated from the front or back, respectively, and the MRA was generally increased above this frequency. Results for narrow-band noise stimuli were similar. Results are discussed with respect to the available interaural cues and physiological mechanisms of sound localization in the gerbil.