Senior Design - Testing Hearing in Dogs

Veterinarians use a method called Brainstem Audio Evoked Response (BAER) to test for hearing loss in dogs. One common use is to test litters of certain breeds (e.g. dalmations) that are genetically pre-disposed to partial deafness. The test requires a variable-amplitude click-tone generator, and a sophisticated amplifier to record nerve signals from tiny electrodes placed painlessly just under the skin on the scalp. The equipment normally used for this is expensive (about $25,000) and large in size.

The objective of this project was to design a miniaturized BAER stimulator and amplifier that would interface with a veterinarian's desktop computer at a cost of less than $2,000.

Three groups of five students each worked for two quarters (20 weeks). Each group worked independently, resulting in three distinct designs. All three designs used high-performance instrumentation amplifier front-ends, followed by several stages of voltage gain and filtering. Two designs used commercially available PC interface boards for data acquisition, while the third design used an external conversion board and interfaced to the PC through a serial port.

Click-tone stimulator circuit used in the BAER project. The headphone jack is on the left. Connectors for power supply and computer interfacing are on the right.