Peak limiting is just one of a number of processes that can be applied to an audio track, but it may be the most common and most damaging of the amplitude modifying effects. The basic idea of any dynamic processor is to alter the natural amplitude variations as produced by a musician. As any performer will tell you, it’s virtually impossible to play any two notes or events exactly the same. Machines do this very well but humans don’t. Of course, great performer produce great performances specifically because they are able to subtly alter the loudness, pitch, and timing of their music.
A peak limiter is an automatic process that detects the amplitude of an instantaneous musical element or sound and has the ability to attenuate the signal level. There are a bunch of parameters associated with a peak limiter that allows the engineers to fine tune the processing with regards to the attack and release of the processing as well as the amount of reduction that will be applied. There’s also a knob that can be used to “make up” the gain that is lost due to limiting.
During the pre-digital days of record engineering, we would use dynamic processing sparingly on vocals, guitars, drums, and percussion instruments as a preventative measure against overloads and distortion. A singer has the ability to quickly change dynamics. One moment they’re singing softly and the next they belt out a note that sends the engineer scrambling for the input fader or record level knob. A peak limiter provides a measure of safety in those instances. No one can react fast enough to an instantaneous peak nor would you want to instantly pull the fader down 20 dB. Instead, the limiter detects the increasing level and over a small amount of time (usually 15-25 ms) it reduces the amplitude.
Peak limiters can also be used to shape a sound creatively. If the engineer wants to “tighten” up the bass part and smooth out the dynamics, a peak limited with long attack and release times and an aggressive gain reduction ratio can do the trick. Does this remove some of the player’s intentions? Of course, but if a producer or engineer feels that the music would benefit from that type of signal processing then it’s there choice to do whatever they want.
In a well-equipped analog studio, there might be a dozen dynamic processors. The outboard rack would house some peak limiters, some gates, expanders, program limiters, and hybrid devices. But these machines were used for specific reasons…and there were treated as special. These days every input or track in Pro Tools can have a slew of dynamic processors activated. The input microphone can be compressed, the bus output can have a limiter in line, and during the mixdown yet another dynamics processor might be applied…and all of this happens prior to the mastering session.
It’s almost as if recording engineers and mastering guys are in a competition to see who can create the loudest records. They’re winning and we’re losing. If you think you’re better off going to a live event to avoid this sort of dynamic intrusion…think again. All of the same processes are used during live concerts, too.
There’s a place for dynamics tools in crafting a hit record but consumers have no say in what they prefer. And unfortunately younger listeners have never heard a track with real world dynamics.