This is a stereo sound file
Listen through headphones with loudspeakers turned off

This is the Deutsch's Octave Illusion. Listen through high quality stereo headphones with the loudspeakers turned off.  (Don’t expect to hear the illusion via loudspeakers in a normal room environment.) Also make sure that the two headphone channels are carefully balanced for loudness.

If you hear a high tone in one ear and a low tone in the other ear, decide which ear is hearing the high tone. Then reverse the earphones while the pattern is playing, and decide again which ear is hearing the high tone. Most righthanders hear the high tone on the right and the low tone on the left, regardless of how the earphones are positioned. Lefthanders and ambidextrous people are more varied in terms of where the high and low tone appear to be coming from.  They are also more likely to obtain complex percepts, such as three different tones that often change their apparent locations in space.

This audio example is presented here in .WAV format.

  Play Deutsch's Octave Illusion (5.2 Mbytes)

The next sound file presents Deutsch’s Octave Illusion first with the two channels in stereo, then with the channels mixed together, and then with the channels in stereo again. Notice that when the two channels are mixed together you only hear a single tone with clicks occurring four times a second. Yet when the two channels are presented in stereo, a pattern of high and low tones occurs instead.   

  Play the illusion in stereo with the channels mixed (4.8 MBytes)

When listening to this sound file, it is best to use equipment with a flat frequency response, so as to avoid spectral distortion. Features that alter the signal in any way, such as spatialization features, should be turned off. Compression algorithms should be avoided, in particular for the stereo illusions. And make sure that the playback amplitude is not too high.

See the Technical Notes for more information.