Digital audio is a digital representation
obtained by sampling
of audio input at a regular interval
The process works like this:The original sound is produced by the movement of air. For almost all sound, this movement is an alternating of high and low pressure wavefronts.A transducer represents this as an electrical signal. The high pressure wavefronts become higher voltage signals and the low pressure wavefronts become lower voltage signals.Next, this electrical signal is routed to a device known as an Analog to Digital Converter (or ADC, for short). The ADC checks the voltage at a regular interval (this interval is usually referred to as the sampling rate) and converts the voltage of each sample into a number.
The stream of numbers that result from this process is digital audio.