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Sketchpad Series

Perceptual Judgments of Auditory Fractal Stimuli

Poster Session F - Tuesday, April 1, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Mahboubeh khoddam¹ (mkhoddam@uoregon.edu), Richard Taylor², Margaret Sereno¹; ¹Integrative Perception Lab, Department of Psychology, University of Oregon, Eugene, OR, United States, ²Material Science Institute, Department of Physics, University of Oregon, Eugene, OR, United States

Fractals, exhibiting self-similarity across scales, are common in nature and artificial phenomena. In audio, fractal properties are often represented by a power law spectrum (1/f^α). While the impact of fractal complexity on visual perception has been well-documented, its influence on auditory perception remains relatively unexplored. This study investigates how variations in auditory fractal complexity, represented by differing α values, influence subjective auditory judgments, including relaxing, engaging, appealing, naturalness, complexity, interesting, and irritating. A set of auditory stimuli was generated using MATLAB, including color noise and amplitude-modulated color noise with varying α values. Ninety-one participants rated the stimuli on 5 perceptual dimensions using a slider scale in a randomized block design. Data collection and presentation were conducted in PsychoPy3, and precise exclusion criteria ensured high data quality. Results revealed significant interactions among α value, stimulus type, and judgment condition. Ratings for "relaxing," "appealing," and "naturalness" increased with α values, suggesting a preference for moderate fractal complexity, while "irritating" ratings decreased. In contrast, ratings for "complex" remained relatively stable regardless of α value, while "interesting" and "engaging" judgments exhibited steady increases. Stimulus type also influenced judgments, with color noise receiving consistently higher ratings than amplitude-modulated patterns in specific conditions. These findings highlight the important role of fractal complexity in auditory perception, with implications for designing soundscapes, therapeutic environments, and multimedia applications. Understanding how fractal properties influence auditory experiences provides valuable insights into natural and artificial sounds' cognitive and emotional processing, offering potential strategies for enhancing acoustic environments.

Topic Area: PERCEPTION & ACTION: Audition