For a specified signal, the minimum effective sound pressure level of the signal that is capable of evoking an auditory sensation in a specified fraction of the trials. The characteristics of the signal, the manner in which it is presented to the listener, and the point at which the sound pressure level is measured must be specified. Also called threshold of detectability. Unless otherwise indicated, the ambient noise reaching the ears is assumed to be negligible. The threshold is usually given as a sound pressure level in decibels, relative to 0.0002 microbar. Instead of the method of constant stimuli, which is implied by the phrase a specified fraction of the trials , another psychophysical method (which should be specified) may be employed.

[[Category: Acoustics]]