Audio: The Basics

During the months of February and March 2007, Xavier University of Lousiana's Art Department and New York University's Interactive Telecommunications Program worked together to develop a digital storytelling curriculum at the former. That collaboration gave birth to the basic audio tutorial you are reading.

Over the course of the next few months, this page will be expanded as an extensive glossary of audio concepts.

M–Audio Micro Track 24/96 Professional 2–Channel Mobile Digital Recorder

Overview

Manuals

Glossary

Balanced Analog Connector
"In a balanced line, two insulated wires carry the signal voltage, but one of the wires carries a 180– phase–inverted version (inverted by the transmitting amplifier). Neither of the two signal lines is tied to ground. A shield for deflecting outside signals is connected to ground and wraps around both signal wires. The circuit to which the cable attaches at both ends passes differential signals, meaning that there must be a difference in voltage between the two conductors for current to flow. Since one signal is 180 degrees out of phase, there is always a voltage difference between the two signals. Hence the audio signal will always pass through the differential input stage. Such a circuit exhitibts the property of common mode rejection, which is the key to the noise immunity of balanced lines. If outside interferences leak through the shield they inevitably contaminate both conductors. Hence this "common mode" signal is rejected by the input circuit."

— The Computer Music Tutorial, Curtis Roads
Decibel
For the purposes of audio, a decibel, or dB, is a measurement of intensity. Zero dB is total silence, while a lawnmower is about 90 dB. (Hearing damage begins to occur at about 85 dB.)
RCA Outputs
Also known as phono plugs, RCA outputs are typically coded red for the right channel and white, or sometimes black, for the left.
TRS (Tip–Ring–Sleeve)
The tip–ring–sleeve, or TRS, configuration of a phono, or RCA, jack, used originally by the telephone company, refers to the left, right, and ground signals, respectively, of a 1/4", 1/8", or miniature connector. You can identify the TRS configuration by holding the connector in your hand with the top facing the ceiling. The hourglass–shaped tip is the left signal, the short band between the black insulating bands is the ring, and the long shaft that connects to the base of the connector is the sleeve.
wav
Developed by Microsoft and IBM, a .wav, or waveform, file is one that contains digitized audio, in most cases, in an uncompressed form. Without compression, a wav file is known as lossless because the integrity of the source that the wav file duplicated was preserved. For example, if you put a CD in your CD–ROM drive and copy its contents to your computer, the copied files represent that CD's tracks in some lossless format. If you use a Windows machine for the copy, then each track is likely to have a .wav extension. If you copy the files using a Macintosh computer, then each track is likely to end in the Mac lossless version of .wav, .aif or .aiff.