Aural critical band
That frequency band of sound, being a portion of a continuous-spectrum noise covering a wide band, that contains sound power equal to that of a simple (pure) tone centred in the critical band and just audible in the presence of the wide-band noise.
Note: 1 By "just audible" is meant audible in a specified fraction of the trials.
Note: 2 The use of the aural critical band to estimate masking should be limited to masking by noises having continuous spectra without excessive slopes or irregularities and to cases where masking exceeds 15 dBdeciBel.
Note: 3 In order to be just audible in a wide-band continuous noise, the level of a simple tone in decibels must exceed the spectrum level of the continuous noise (at the same frequency) by ten times the logarithm to the base 10 of the ratio of the critical bandwidth to unit bandwidth.
Please note that this is the term as it stands in the original IALAInternational Association of Marine Aids to Navigation and Lighthouse Authorities - AISM Dictionary edition (1970-1989)