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On the externalization of sound images
1Department of Physics, Michigan State University, East Lansing 48824, USA. hartmann@pa.msu.edu
The Journal of the Acoustical Society of America
|June 1, 1996
Summary
Sound externalization relies on specific ear canal signal characteristics. Interaural phase at low frequencies and interaural level differences across all frequencies are key, while spectral profiles must be realistic for accurate sound perception.
Area of Science:
- Acoustics
- Psychoacoustics
- Auditory Perception
Background:
- Listeners naturally perceive real-world sounds as externalized and accurately located.
- Headphones can create virtual sound images, but replicating externalization requires understanding specific signal cues.
Purpose of the Study:
- To identify the crucial signal characteristics in the ear canal responsible for the perception of sound externalization.
- To investigate the role of interaural phase, interaural level differences, and spectral profiles in auditory externalization.
Main Methods:
- Utilized headphones for experimental control and a psychophysical discrimination method to measure externalization.
- Systematically modified synthesized headphone signals, starting from a baseline mimicking real-world sound, to assess changes in externalization perception.
- Employed both discrimination tasks and listener ratings to evaluate externalization.
Main Results:
- Externalization depends on interaural phases of low-frequency (<1 kHz) components, but not high-frequency components.
- Interaural level differences are important across all tested frequency ranges.
- Realistic spectral profiles in both ears are necessary; interaural difference spectrum alone is insufficient.
- Dispersion around the head is not critical; an optimal interaural time difference suffices.
Conclusions:
- Sound externalization is primarily governed by low-frequency interaural phase and broad-frequency interaural level differences.
- Accurate spectral representation in both ears is essential for convincing virtual auditory experiences.
- These findings advance the understanding of spatial audio perception and headphone-based sound reproduction.