| Adaptive TRansform Acoustic Coding — a compression technique used to fit the same amount of data as that of a 120 mm CD on a 64 mm MiniDisc. ATRAC uses established psychoacoustic principles to compress audio data to approximately one-fifth of its original size, with virtually no loss in sound quality. The threshold of hearing principle states that the sensitivity of the human ear is frequency dependent. Two tones of the same level but at different frequencies will not be heard at the same loudness. Another principle used is the masking effect. That is, softer sounds become inaudible when louder sounds at similar frequencies are present. |