Intensity as the Dominant Cue for Minimum Audible Angle in Young Adults
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Abstract
Background and Aim: The Minimum Audible Angle (MAA), defined as the minimum perceivable angular disparity among sound sources, is the most frequently used measure of spatial acuity in psychophysics. While conventionally free-field loudspeaker arrangements measure MAA, virtual auditory methods offer flexible alternatives. The study aimed to determine which stimulus characteristic—intensity level, type, or duration—most influences MAA in normally hearing young adults.
Methods: Using a repeated-measures design with 30 healthy adults aged 18-30 years, spatialized stimuli generated by the 3D Tune-In Toolkit were presented over headphones at three levels (45-, 55-, and 65-dB SPL), durations (250, 500, and 1000 ms), and stimulus types (complex tone, pure tone, and white band noise). MAA thresholds were determined using a psychometric staircase procedure with a two-down one-up rule in a three-interval forced-choice task.
Results: Three-way repeated-measures ANOVA showed significant main effects of stimulus type and intensity level (p < 0.001), while duration had no significant effect but interacted with level and stimulus type (p < 0.001). Post hoc comparisons revealed eight significant stimulus-type pairs and nine level pairs after Bonferroni correction (α = 0.02), with complex tones and higher intensity producing lower MAA thresholds. Multiple regression showed only stimulus intensity significantly predicted MAA.
Conclusion: The findings demonstrate that higher intensities yield optimal spatial acuity and confirm the reliability of virtual headphone-based methods.
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