Bitrate is the term for the amount of compression applied to a WAV file. An mp3 file with a bitrate of 128 kbps (stereo) is compressed so that every second of audio data of the WAV file is encoded with 128 kilobits per second (64 kb for the left channel, 64 kb for the right channel). With mp3, a total bitrate of as high as 320 kbps is allowed.
| Bitrate (kbps) | Relative Size | Relative Quality |
|---|---|---|
| 64 and lower | Files are small. Good for sending through the internet for low-speed modems. | There's no sense in encoding in stereo at these low bitrates as it results in really low quality. If the files are encoded in monaural (mono), the quality is great, but it's only one channel |
| 96 - 112 | Files are still really small. Good to use as previews for downloading off the internet. | When using joint-stereo, these files are bearable. The difference between these mp3's and the original WAV's are easily identified. High frequencies are not encoded in these low bitrates. Also audible artefacts (distortions introduced by the insufficient number of bits needed to encode the sound) are introduced. |
| 128 - 160 | Files are about 1/10 the size of the original WAV file. | This bitrate has been the most popular on the internet for some time. It has been a good trade-off between quality and size and 128 is the “standard”. However, with access to faster connections to the internet and larger storage capacities of computers more and more people are moving to higher bitrates. 128 kbps is somewhere around or above tape cassette quality. High frequencies are still weak. |
| 192 - 224 | Files are larger and become harder to handle in terms of downloading & uploading for people with slow connections. | Quality increases with each progression. These become indistinguishable from the original WAV's for people listening on computers equipped with average sound cards and speakers. |
| 256 - 320 | Files are only about 1/5 the size of the original WAV file. | Professional listening tests have been conducted with 256 kbps. Expensive hi-fi equipment was used and it is now widely accepted that 256 kbps is transparent (no audible difference between mp3 and WAV file for most music). For those of you that want the ultimate quality and have the storage, this is the bitrate to use. |