Digital data is comprised of “bits” (see WFTD “Bit“) which are organized into “words” representing sample values. Word clock is a synchronizing signal based on the sample rate or the speed with which sample words are sent over a digital connection. Word clock is used by the receiving digital device to decipher where in the data stream each sample word ends, as well as whether the word belongs to the right or left channel (in a stereo signal).
When transmitting digital audio signals from one piece of gear to another, it is therefore important that their clocks be synchronized (i.e. the receiving device is made to “slave” its clock to the transmitting device’s internal clock, or the whole system is locked to an external house sync signal or master clock), otherwise the sample words in the data stream will not be “lined up” correctly in the receiving device, possibly causing clicks, pops and other audio degradations.