The scale illusion has a different pattern presented to each ear. The pattern of notes in each ear sounds rather random and violates many of the gestalt principles of hearing melodies that were discussed earlier. Next, try listening with headphones on both ears and play the sequence. Most people hear scales playing in each ear going in the opposite direction. A descending and ascending scale is heard in one ear and an ascending and descending scale is heard in the other ear. You can figure out how the scales can be assembled from what is played in each ear if you start with the first note for the right ear. With this note you are at the top of a scale. The next note for this descending scale is found in the second note played but in the left ear. The third note is back in the right ear, and so forth.
Refer back to the role of the gestalt principles in the perception of melody discussed earlier. For example, proximity and good continuation are important principles in hearing a melody amid a whole constellation of notes. The tunes played in each ear violate both of these gestalt principles, but our perception follows both of them very nicely. Compare the two parts of Figure 13.x and see how the perception follows the gestalt laws much better than what is played in each ear. It seems our need for coherent perception overrides what ear the sound arrives in, even when the sound is limited to one ear as when headphones are used.
In this illustration, you can listen to the scale illusion. In particular, listen to the notes that will be played in each ear separately first before using the headphones to listen to the being played at the same time. Read more here.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
Below is a list of the ways that you can alter the illustration. The settings include the following:
Play: will play to tone combination alternating which ear gets the lower
and higher pitch.
Play Series: will play a series of tone combinations to help you hear the octave illusion.
Play in: play the tones in the Left Ear only, Both Ears, or the Right Ear only. The octave illusion can be only experienced when the tones are played to both ears.
Duration (ms): the duration of the tones in milleseconds.
Pressing this button restores the settings to their default values.