They are not the same as equal-loudness contours, which are a set of curves representing equal loudness at different levels, as well as at the threshold of hearing, in absolute terms measured in dB SPL ( sound pressure level ).
12.
Standard measurement practice of speaker sensitivity is driving 1 watt electrical power to the source, with the receiver 1 meter away from the source, and measuring the resulting acoustical power in dB relative to the threshold of hearing ( defined as 0 dB ).
13.
This is not the best threshold found for all subjects, under ideal test conditions, which is represented by around 0 phon or the threshold of hearing on the equal-loudness contours, but is standardised in an ANSI standard to a level somewhat higher at 1 kHz.
14.
The spectral pitches differ in perceptual salience since their sound pressure levels differ physically, they lie at different distances above the threshold of hearing, they mask each other ( and therefore lie at different distances above the masked threshold ), and may or may not lie in a region to which the ear is particularly sensitive ( a dominance region of pitch perception ).
15.
It is important to listen to it in the way it was composed, near the threshold of hearing . " ( liner notes ) Her collage piece " SUM ( State of the Union Message ) " is included on the " Lesbian American Composers " collection ( 1998 CRI : 780 ) . " SUM " and " DUMP " ( 1970 ), also a sonic collage, are her best known pieces.
