BS 3383:1988 pdf download.Normal equal-loudness level contours for pure tones under free-field listening conditions.
2 References ISO 131, Acoustics — Expression of physical and subjective magnitudes of sound or noise in air. ISO 266, Acoustics — Preferred frequencies for measurements. ISO 389, Acoustics — Standard reference zero for the calibration of pure tone air conduction audiometers.
3 Definitions For the purposes of this International Standard, the following definitions are used, the conditions of applicability stated in clause 1 being understood, where appropriate.
3.1 loudness that attribute of auditory sensation in terms of which sounds may be ordered on a scale extending from soft to loud
3.2 loudness level of a given sound, the sound pressure level of a reference sound, consisting of a sinusoidal plane progressive wave of frequency 1 000 Hz coming from directly in front of the listener, which is judged by otologically normal persons to be equally loud to the given sound. Loudness level is expressed in phons
3.3 equal-loudness level function for a pure tone of given frequency or for a narrow band of noise of a given frequency band, the relation between loudness level, expressed in phons, and sound pressure level, expressed in decibels
3.4 equal-loudness level contour a curve in the sound pressure level/frequency plane, connecting points the co-ordinates of which represent pure tones or narrow bands of noise judged equally loud
3.5 normal equal-loudness level function the equal-loudness level function corresponding to the modal judgement of otologically normal persons within the age limits from 18 to 30 years inclusive
3.6 normal equal-loudness level contour the equal-loudness level contour corresponding to the modal judgement of otologically normal persons within the age limits from 18 to 30 years inclusive.
3.7 hearing threshold the level of a sound at which, under specified conditions, a person gives 50 % of correct detection responses on repeated trials
3.8 otologically normal person a person in a normal state of health who is free from all signs or symptoms of ear disease and from excess wax in the ear canals, and who has no history of undue exposure to noise
3.9 minimum audible field (MAF) at a specified frequency the sound pressure level of a pure tone or a narrow band of noise corresponding to the modal value of the binaural hearing threshold of otologically normal persons within the age limits from 18 to 30 years inclusive
3.10 critical bandwidth the widest frequency band within which the loudness of a band of continuously distributed random noise of constant band sound pressure level is independent of its bandwidthBS 3383 pdf download.