Psychoacoustics / Music

The subjective impression of FREQUENCY, in the same sense that LOUDNESS is the subjective sense of the INTENSITY or AMPLITUDE of a sound. As such, pitch is a psychoacoustic variable, and the degree of sensitivity shown to it varies widely with people. Some individuals have a sense of remembered pitch, that is, a pitch once heard can be remembered and compared to others for some length of time; others have a sense of absolute pitch called PERFECT PITCH.

The pitch of a TONE or NOTE allows it to be placed in a musical SCALE; thus notes of a scale are often called pitches, and given names (A, B, C, C#, doh, re, mi, etc.).


The smallest degree of pitch discrimination between two pitches depends on their intensity and frequency range (see DIFFERENTIAL THRESHOLD). Under the best conditions, a person with good hearing can discriminate about 1400 different pitches, of which 120 are used in the western scale of equal temperament. The lowest pitch corresponds to the lowest frequency giving a sensation of TONE, around 20 to 30 Hz. The highest pitch depends on the highest audible frequency, which varies with age and especially noise exposure, but lies generally in the range of 15 to 20 kHz with younger people.


The sense of pitch depends on the intensity of the tone, as shown in the graph; below 1000 Hz, pitch tends to drop with increasing loudness, and above 1000 Hz, tends to rise. A tone must have a certain duration for pitch to be ascribed; if not, it is heard as a CLICK. The nature of the SPECTRUM of a COMPLEX TONE will affect the sense of pitch as well. A note rich in OVERTONEs will appear to have a more definite pitch than a SINE TONE of the same frequency and intensity, for instance. The pitch of the complex tone will correspond to its FUNDAMENTAL frequency. Compare: SIMPLE TONE.

The change in pitch in percent with loudness for various frequencies as indicated on the curves (from Olson, Music, Physics and Engineering, Dover, 1967, p. 251, after Stevens, used by permission).

In a very complex INHARMONIC spectrum, however, a sound may appear to have several pitch components. A sound with a continuously changing pitch is called a GLISSANDO. A pitch change caused by a moving sound source or observer is termed DOPPLER SHIFT.


Sound Example: Simple tone (sine wave).

Sound Example: Complex tone (triangle wave) with the same frequency as the sine tone.

Sound Example: 1 kHz tone with duration of 40 ms being shortened to a 2 ms broad-band click where it loses its sense of pitch.

Sound Example: Cello note (harmonic spectrum).

Sound Example: Gamelan instrument (inharmonic spectrum).

The pitch ascribed to a complex tone or sound may not necessarily correspond to a frequency that is physically present in the sound. For instance, if a spectrum consists of harmonics beginning with the second or higher harmonic, the sound will still be heard as having the pitch of the fundamental, called the periodicity pitch or the missing fundamental (see FUNDAMENTAL for further discussion). In summary, Schouten has stated, "The pitch ascribed to a complex sound is the pitch of that component to which the attention, either by virtue of its loudness or of its contrast with former sounds is strongest drawn. Therefore the pitch of a complex sound may be different depending on the circumstances under which it is heard." See reference under RESIDUE.

The distance between two pitches is called an INTERVAL. However, equal frequency intervals do not always give the same sense of pitch distance, depending on the RANGE in which the interval is situated. For instance, a FIFTH in a high frequency range may seem to be a smaller pitch distance than a THIRD in a lower range. The MEL scale is an attempt to measure this variation. An alternative theory of pitch perception judges each note in terms of its chroma or distinctive tone colour and its tone-height. In this system, pitches may be arranged in a helix instead of a one-dimensional order, with the recurring loops of the helix at OCTAVE intervals. See: LINEAR.