File format for audio, stored as waveform, using the Pulse Code Modulation (PCM). File size depends on the type of sound (mono or stereo), the bit rate and the sampling frequency. File size for one minute audio can typically vary between 600kB and 25MB.
WAV is a file container. A wide variety of codecs can be used. For Windows systems the most often used codecs are Microsoft Adaptive Differential Pulse Code Modulation (MS ADPCM) and uncompressed Pulse Code Modulation (PCM).
MP3 is an audio compression technology that is part of the MPEG-1 and MPEG-2 specifications.
The Fraunhofer IIS-A started in 1987 to work on perceptual audio coding. In a joint cooperation with the University of Erlangen (Prof. Dieter Seitzer), the Fraunhofer IIS-A finally devised the algorithm standardized as ISO-MPEG Audio Layer-3 (IS 11172-3 and IS 13818-3).
Digital Audio uncompressed = 44,1 kHz sample rate / 16-bit samples / 2 audio channels needs a bandwidth of 1.4 Mbps. 1.400 Mbit represent one second of stereo music in CD quality.
Using MPEG audio coding, it is possible to shrink down the original sound data by a factor of 12, without audibly losing sound quality.
A MPEG-1 Audio, Layer 3 (MP3), "near CD-quality" stereo audio stream needs only 128kbit/s.
Factors of 24 and even more still maintain a sound quality that is significantly better than what you get by just reducing the sampling rate and the resolution of your samples.
Performance Data of MPEG Layer-3:
|Sound Quality||Bandwidth||Mode||Bitrate||Reduction ratio|
|similar to FM radio||11 kHz||stereo||56...64 kbps||26...24:1|
|near-CD||15 kHz||stereo||96 kbps||16:1|
Audio-coding standard, originally developed as a part of the MPEG-1 specification, later updated for the MPEG-2 specification. It is not often used anymore.
CD audio can be stored as computer files with the extension '.cda'.