Audio Processing 101
By Cornelius Gould
What Is Audio Processing?
To help with understanding some of the terms used here, I suggest you check out Audio Processing University part One.
Audio processing has its roots in the early days in radio stemming from the desire to automatically control peak levels in a broadcast chain. The reason for this came about as a way to assist radio console operators. In this case, the console operators literally controlled the modulation of a broadcast station by manually turning up and / or down the levels on their console. If the levels were to peak above 100% on the board, then the transmitter would operate illegally. So, the operators had to act quickly when this situation arose to keep distortion and illegal over-modulation to a minimum.
This is where the automatic peak limiter came into play. Physically, the peak limiter would be a device with audio inputs and outputs. The unit operates by monitoring the levels feeding into it, and make audio level corrections anytime the levels exceeded a pre-set reference point (or threshold). Usually this reference point was set to 100%.
If program levels remain below 100%, the limiter assumes a “unity gain” state. That is, the audio levels on the input equal the output. If the audio exceeds 100%, then the output of the limiter is reduced by an equal amount. That is, if the input is, say, 175%, then the output of the limiter is 75% less than the input. Continue reading Audio Processing 101 →