What does "compression" like?

Hi Reb.

Compression usually refers to compression of dynamics, where the softest sounds are louder and loudest lower than "normal".

How applied or not is part of how most any recording is made.

Its usually done to make all parts of the recording able to be heard more consistently, especially at lower volumes and/or when external background noise is present..

The negative for audiophiles often comes in as reducing the "jump factor" often associated with good dynamics, and also distorting the presentation of individual acoustic instruments compared to live playing.

The big negative that can come into play with dynamic range compression is when waveform peaks are clipped off as part of the process. This is the most significant and generally offensive kind of distortion often but not always introduced as part of dynamic compression.

Agree with the above posts. A good example of what compression sounds like would be if you listen to a classical FM station on your tuner for a big orchestral piece like a Mahler symphony. At the climaxes where the whole orchestra is playing full blast, you'll notice how the volume drops dramatically. For a contemporary pop recording, as a general rule that won't happen because the recording itself has had its dynamic range compressed, so the difference between loud and soft parts is minimal.

Compression comes in two forms. Digital file compression, such as MP3s. It discards information that for portable, uncritical listening at low levels won't be disturbing. However, today, when you can hold gigabits of data on a USB drive the size of a fingernail, there's no longer any need for file compression.

The other compression is dynamic compression. This also is no longer necessary for most digital recordings. 24bit provides a 144 dB dynamic range—that goes from just barely audible to painfully loud and hearing damage. There's no reason for music recordings to be compressed, because, for example, the range of sounds you'll hear from a symphony orchestra, from the softest solo instrument to the loudest passages with all the brass blaring and the percussion going full force, spans about 60 dB. Compression kills the expressive dynamics that musicians painstakingly put into their music. It takes away the transient spikes that give percussion its punch.

How it sounds is difficult to describe, because it doesn't produce any gross distortion that would make you cringe.

Here's a link that has both a visual and audio example of dynamic compression, plus a couple of additional links.

Made an error in the url, try this dynamic compression.

If it always sounds loud, no matter the volume of playback, it is compressed.