Summer 2012

A Device to Learn how People Hear

Dr. Pavel Zahorik from the University of Louisville, KY contacted PSL to develop a device for auditory research. The focus is to get a better understanding of how each individual hears sound with consideration to an individual’s physical differences. PSL engineers were asked to design a mechanism that will aid in the research being conducted at the Department of Psychological and Brain Sciences at the University of Louisville.

Dr. Zahorik provided the following description of the purpose of the speaker mover: 
“The human head and external ears modify incoming sound. The nature of this modification depends on the direction of the sound source relative to the listener. The human auditory system uses this information to decode directional information in the sound reaching the ears.  It is important to be able to accurately measure the acoustical transfer functions that describe the sound transmission from a free-field source to the ear drum for many directions surrounding the listener. Such measurements are typically referred to as head-related transfer functions, or HRTFs, and are referenced relative to the same sound transmission in the absence of the head. The new robotic device will greatly facilitate the HRTF measurement process by allowing fast and accurate positioning of a reference loudspeaker used for the measurements. Such fast and accurate positioning is critical because a full set of HRTF measurements will typically involve over 500 measurement directions!”

The speaker mover is a mechanism that moves a speaker around the head of a blindfolded listener, at a radius of about 1.63 meters (64"), from 45 degrees below to directly overhead, at any angle relative to forward. The speaker mover incorporates extremely quiet drives, sound absorbing isolating materials, and geometry to deflect any indirect-path sound propagation away from the experimental subject. It includes encoders, home reference, and limit switches for both rotating axes. An adapter plate and counterweights enable use with a selection of speakers.

Construction, assembly and checkout were completed at PSL. It was shipped after development and testing of a graphical operator interface. The mechanism has been installed in an anechoic chamber in Louisville by PSL personnel and was tested on-site.

This is a video of the speaker mover in action: (requires Quicktime)

Learn more about Dr. Zahorik’s research.


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