 However, there also exist 44.1 kHz/24-bit, 48 kHz/24-bit and 88.2 kHz/24-bit recordings that are labeled HD Audio.Research into high resolution audio began in the late 1980s and high resolution audio content started to become available on the consumer market in 1996.High-resolution audio is generally used to refer to music files that have a higher sampling frequency and/or bit depth than that of Compact Disc Digital Audio (CD-DA), which operates at 44.1 kHz/16-bit.