(1) In analogue audio, the width of a frequency band for a transmission channel, from a lower to an upper frequency limit. The limits are defined in terms of signal attenuation, in decibels, relative to the level at the centre of the band. See also decibel. (2) In digital data transmission, the available data throughput for a transmission channel. Digital bandwidth is typically expressed in terms of bits or bytes per second. See also bit rate.