Perceptual attack time
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Perceptual Attack Time (often abbreviated "PAT") is a subjective measure of the time instant at which a musical sound's rhythmic emphasis is heard. It is analogous to the perceptual centre (aka "p-centre") in speech.
It is different from both the physical onset (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 milliseconds, 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.