Purpose:Demonstrate individually the phenomena of binaural beats and diplacusis.
Description:Two sine wave oscillators present their signals separately to the two ears using stereophones through the Diplacusis and Binaural Beat Demonstrator. Binaural beats occur in the brain when the frequencies of the two waves are very close, but the two waves do not physically mix to create first order or monaural beats. The amplitude of the two waves is kept small enough to avoid bone conduction. A subject is asked to match the pitch of the two oscillators under these circumstances, which is very difficult even for most trained musicians. Diplacusis refers to the inability to match pitches when the two tones are presented to separate ears. The two tones can be combined by flipping a switch on the Demonstrator, and the sum wave can be displayed on the oscilloscope. Several listeners can observe the proceedings through individual stereophone jacks.