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How do owls localize interaurally phase-ambiguous signals?
K Saberi1, H Farahbod, M Konishi
1Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. kourosh@caltech.edu
Summary
Barn owls, like humans, use sound timing differences to locate sounds. However, owls experience "phase-ambiguity" with pure tones, misinterpreting sound direction due to signal periodicity.
Area of Science:
- Auditory neuroscience
- Animal behavior
- Bioacoustics
Background:
- Animals, including humans and owls, use interaural time differences (ITDs) to determine sound source direction in the horizontal plane.
- Human sound localization can be ambiguous with narrowband signals due to phase-ambiguity, where ITDs are confused with their periodic equivalents (ITD +/- nT).
- While ITD-sensitive neurons in mammals and birds respond to phase-equivalent stimuli, it's unclear if animals exhibit behavioral phase-ambiguity.
Purpose of the Study:
- To investigate whether barn owls exhibit phase-ambiguity in sound localization when presented with narrowband tonal stimuli.
- To determine if owls' perception of sound direction is affected by the periodic nature of pure tones.
Main Methods:
- Utilized sound-induced head-turning responses in barn owls (Tyto alba) to measure perceived sound source direction.
- Presented pure-tone auditory stimuli through earphones to systematically vary the interaural time difference (ITD).
- Analyzed head-turning angles as a function of ITD to infer the owls' localization judgments.
Main Results:
- Both owls demonstrated head-turning responses that varied sinusoidally with the presented ITD.
- One owl consistently localized the sound based on the smaller ITD value.
- The second owl consistently localized the sound based on the larger ITD value (ITD - T), indicating phase-ambiguity.
Conclusions:
- Barn owls exhibit behavioral phase-ambiguity when localizing pure-tone auditory stimuli.
- This finding suggests that the mechanism of sound localization in owls, similar to humans, can be susceptible to ambiguity with narrowband signals.
- The study highlights the complexity of auditory scene analysis and the potential for perceptual ambiguities in biological sound localization systems.
