The number of computer bits conveyed or processed per unit of time. Normally expressed in kilobits per second (kbps). For an uncompressed, PCM file, kbps bit rate is sample rate multiplied by sample format multiplied by number of channels, divided by 1000, giving 1411 kbps for Red Book WAV or AIFF. Rates are much lower for compressed or lossy formats like MP3. For MP3 at constant bit rate, reducing sample rate does not reduce the bit rate and hence does not make the MP3 smaller, except for 11025 Hz and below.