Comparing Digital and Analog Recording

Analog recording versus digital recording compares the two ways in which sound is recorded and stored. Actual sound waves consist of continuous variations in air pressure. Representations of these signals can be recorded using either digital or analog techniques.  An analog recording is one where a property or characteristic of a physical recording medium is made to vary in a manner analogous to the variations in air pressure of the original sound.

Generally, the air pressure variations are first converted (by a transducer such as a microphone) into an electrical analog signal in which either the instantaneous voltage or current is directly proportional to the instantaneous air pressure (or is a function of the pressure). The variations of the electrical signal in turn are converted to variations in the recording medium by a recording machine such as a tape recorder or record cutter—the variable property of the medium is modulated by the signal. Examples of properties that are modified are the magnetization of magnetic tape or the deviation (or displacement) of the groove of a gramophone disc from a smooth, flat spiral track.

The key aspect which makes the recording analog is that a physical quality of the medium (e.g., the intensity of the magnetic field or the path of a record groove) is directly related, or analogous, to the physical properties of the original sound (e.g., the amplitude, phase, etc.), or of the virtual sound in the case of artificially produced analog signals (such as the output from a guitar amp, a synthesizer, or tape recorder effects playback.)  A digital recording is produced by converting the physical properties of the original sound into a sequence of numbers, which can then be stored and read back for reproduction. Usually (virtually always), the sound is transduced (as by a microphone) to an analog signal in the same way as for analog recording, and then the analog signal is digitized, or converted to a digital signal, through an Analog-to-Digital converter (an electronic device) either integrated into the digital audio recorder or separate and connected between the recorder and the analog source.

An electrical digital signal has variations in voltage and/or current which represent discrete numbers instead of being continuously mathematically related as a function to the air pressure variations of sound. There are two chief distinctions between analog recording versus digital recording.