The Perception of Pitch

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Pitch perception is fundamental to melody in music and prosody in speech. Unlike many animals, the vast majority of human adults store melodic information primarily in terms of relative not absolute pitch, and readily recognize a melody whether rendered in a high or a low pitch range. We show that at 6 months infants are also primarily relative pitch processors. Infants familiarized with a melody for 7 days preferred, on the eighth day, to listen to a novel melody in comparison to the familiarized one, regardless of whether the melodies at test were presented at the same pitch as during familiarization or transposed up or down by a perfect fifth (7/12th of an octave) or a tritone (1/2 octave). On the other hand, infants showed no preference for a transposed over original-pitch version of the familiarized melody, indicating that either they did not remember the absolute pitch, or it was not as salient to them as the relative pitch.

The note A above middle C played on a piano is perceived to be of the same pitch as a pure tone of 440 Hz. However, a slight change in frequency need not lead to a perceived change in pitch. The just noticeable difference (the threshold at which a change in pitch is perceived) is about five cents (hundredths of a semitone), or about 0.3% in frequency, but varies over the range of hearing and is more precise when the two pitches are played simultaneously. Like other human stimuli, the perception of pitch also can be explained by the Weber-Fechner law.

Pitch may depend on the amplitude of the sound, especially at low frequencies. For instance, a low bass note will sound lower in pitch if it is louder. Like other senses, the relative perception of pitch can be fooled, resulting in "audio illusions". There are several of these, such as the tritone paradox, but most notably the Shepard scale, where a continuous or discrete sequence of specially formed tones can be made to sound as if the sequence continues ascending or descending forever.

Repetition pitch