Perceptual Attack Time (often abbreviated "PAT") is a
subjective measure of the time instant at which a musical sound's
rhythm
Rhythm (from Greek , ''rhythmos'', "any regular recurring motion, symmetry") generally means a " movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions". This general meaning of regular recu ...
ic emphasis is
heard. It is analogous to the
perceptual centre (aka "p-centre") in speech.
It is different from both the physical
onset
Onset may refer to:
*Onset (audio), the beginning of a musical note or sound
*Onset, Massachusetts, village in the United States
**Onset Island (Massachusetts), a small island located at the western end of the Cape Cod Canal
*Interonset interval, ...
(i.e., the time at which the sound's acoustic energy first begins) and the perceptual onset (i.e., the subjective time at which a listener first notices that the sound has begun). For a very percussive sound such as a note played on a closed
hi hat cymbal the perceptual attack time may be just a few
millisecond
A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds.
A unit of 10 milliseconds may be called ...
s, while for a note
bowed slowly on a violin the perceptual attack time may be as much as 50–100 milliseconds after the physical onset.
Applications
Understanding the perceptual attack time of recorded sounds is important when scheduling those sounds to be played by a computer. For example, suppose you want
to
play a melody on a series of notes from different instruments. If the notes' physical onsets are equally spaced, the result will probably sound a little bit unsteady or out of rhythm; to get a rhythmically correct result it's necessary to account for each sound's perceptual attack time, i.e., to schedule the notes so that their perceptual attack times, not their onsets, are spaced according to the rhythm of the melody.
References
* Collins, N. (2006).
"Investigating computational models of perceptual attack time" Proceedings of the 9th International Conference on Music Perception & Cognition (ICMPC9).
* Gordon, J. W. (1987). The perceptual attack time of musical tones. Journal of the Acoustical Society of America, 82(1), 88–105.
* Vos, J., & Rasch, R. (1981). The perceptual onset of musical tones. Perception and Psychophysics, 29(4),323–35.
* Wright, M. (2008
"The Shape of an Instant: Measuring and Modeling Perceptual Attack Time with Probability Density Functions (If a Tree Falls in the Forest, When Did 57 People Hear it Make a Sound?)" Ph.D. Dissertation, Stanford University.
Experimental psychology
Rhythm and meter