Analog & Digital Representation

Naturally occurring sound, as well as the output of musical instruments and sound systems, is a sequence of waves or waveforms. A wave represents the time-progressive strength of the sound as a displacement or excursion from the silent or quiescent state. It is possible to measure and express the displacement numerically. The popular word for "numerical" is "digital". The waveform-like representation is called "analog" representation as opposed to "digitized" or digital representation. The analog wave is digitized by an analog-to-digital converter (ADC) circuit. Conversely, the digitized wave is rendered as a natural (analog) sound by a digital-to-analog converter (DAC) circuit. The sound card of your computer contains an ADC and its complementary DAC.

The sound from a drum, a singer's voice... these are sound signals. These sound signals are converted via the singer's microphone or a pick-up on the instrument to electrical/electronic signals. The electrical signals faithfully follow the original sound signals; hence we call these electrical signals "analog" signals.

We need the converted electrical signals if we are going to use electrical/electronic equipment to process, transmit or store the original sound signals.

Analog signals are better expressed as "linear" signals, whereas digital signals are better expressed as "quantified" or "non-linear" signals.