eli5: how do compresors work? Audio related.


eli5: how do compresors work? Audio related.

In: 12

“The compressor is like your mother. Threshold: the level she asks you to turn the music down. Ratio: How much you turn down the volume after she shouts at you. Attack: How fast you react. Release: How fast you turn the volume back up as soon as she closes the door.”

I won’t get into the electronics of it. But compressors dereases the volume of louder parts of a recording to keep them from overpowering quieter parts. The goal is to make all the sounds roughly the same volume, which reduces gaps in audio when some sounds are quieter or the volume of a voice or instrument varies.

A compressor reduces the dynamic range of an audio signal (reduces the peak to peak amplitude), which allows for a much higher average signal level without clipping / distorting the peaks.

Compression is why when you are watching TV, the ads tend to seem so much louder than your program material. The peaks are at the same level, but the average level of the ad is much higher. The tradeoff is in fidelity and loss of realism. In the ad, the difference in volume between a whisper and a hurricane is minimal. In a high quality recording, the average level has to be significantly lower in order to have sufficient headroom to accurately reproduce the extreme peaks when they occur.

Proper application of compression tames the most extreme peaks in a signal so that they can be reproduced without distortion while maintaining a reasonable average signal level.

The so-called “loudness wars” in recording describe a trend of increasing use of compression in order to record tracks at hotter signal levels, but with a consequent loss of emotion, realism, and dynamics.

Imagine you’re snuggled up with your favorite stuffed animal watching Netflix late at night, but it’s hard to hear the quiet parts. So you turn them up. Then there’s an explosion and you rush to turn it down.

A compressor does that automatically, adjusting levels so that there’s less variation. This making things easier to hear (especially speech) but possibly making them less exciting if you overdo it.

Makes sounds ‘bigger’. Use it to level out sounds by reducing peaks and also increasing the quieter parts of the sound. If done properly you can get a fuller sound from your sample or instrument.

Having your sounds levelled out with a compressor also helps with mixing all your sounds together.

There’s a bunch of other uses too but this would be one of the main uses.