Perceptual sub band/transform

Codecs designed to reduce the data rate and/or size of a digital audio file. The encoder applies a psychoacoustic model to estimate whether, in any particular band of frequencies, the signal strength in that band I above or below the perceptual threshold relative to adjacent frequency bands. If the signal is above that masking threshold, than a spectral coefficient or value is generated to represent the signal in that band and the coefficient becomes the stand-in, or representation of, the actual audio in that band, if the signal is not above the predicted masking threshold, then that band of frequencies is tossed out to reduce the final size of the essence.