Pinna cues determine orienting response modes to synchronous sounds in elevation

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Human Perception

Background:

• Goal-directed orienting responses require the audiomotor system to detect and select target sounds within complex acoustic scenes.
• Segregating synchronous sounds in the midsagittal plane (elevation) is challenging, necessitating dissociation of pinna-induced spectral localization cues.

Purpose of the Study:

• To investigate the human auditory system's ability to segregate synchronous sounds in the midsagittal plane.
• To determine how sound intensity and spatial disparity influence head-orienting responses to simultaneous sounds.

Main Methods:

• Human listeners performed rapid head-orienting responses to single or simultaneous sounds in the midsagittal plane.
• In dual-sound conditions, listeners were instructed to orient to a target sound while ignoring a nontarget sound.
• Localization accuracy and response endpoint distributions were analyzed based on sound level and spatial disparity.

Main Results:

• Accurate localization was achieved with single sound sources.
• In dual-sound conditions, the loudest sound dominated responses, irrespective of target status.
• Response endpoints showed weighted averaging for similar intensities and small disparities, but became bimodal with disparities > 45 degrees.

Conclusions:

• Auditory-evoked responses in sound segregation tasks can be explained by individual ear acoustics (pinnae).
• These findings suggest fundamental differences in target representation and selection principles between auditory and visual systems.