I’m not a huge fan of gates. I’ve never found them to be a “must have” audio processor, and even knowing that their output will get blended into everything else in the mix, I rarely find myself liking their output. For whatever reason, gating almost always sounds unnatural and jarring to me, whereas even a signal that’s been horrifically mangled by a compressor can still have some redeeming qualities in my ears.

Even so, gates can be handy on occasion – and it’s a good idea to know how they work, so that the (hopefully) rare occasion can be risen to.

No, this is not going to be a primer on the basic setup and operation of a gate or expander. It IS going to be a discussion of a nifty feature found on more fully equipped units. I’m talking about hysteresis.

Hysteresis is one of those words which is highly abstract. The definitions you can find tend to make your eyes glaze over. To wit, this example from Google:

“The phenomenon in which the value of a physical property lags behind changes in the effect causing it, as for instance when magnetic induction lags behind the magnetizing force.”

Geeze. Wow.

It all makes more sense when you yank the concepts out of the abstract and into practical reality. And what better reality to use than a direct one, i.e., a problem with a gate.

If you’ve gotten some hands-on time with these dynamic-range expander things, you’ve probably run into the problem of “chatter.” Chatter is the process gain being rapidly adjusted up and down as a signal repeatedly crosses above and below the threshold at short intervals. The signal exceeds the threshold, the processor gain quickly returns to unity, and then the signal drops under the threshold, resulting in the gate slamming the gain back down. Sure, you could increase the attack and release times, but what if you need a fast attack? What if the signal decay time is highly variable? You’re out of luck, chum.

This is where hysteresis can come in handy, by allowing the gate gain (the processor’s “physical property”) to lag behind the signal changes (the effect causing the gain change). In practice, what you might see is a hysteresis setting defined in positive or negative decibels relative to the threshold. What you’re getting is the ability to set a release threshold which is different from the attack threshold.

So, if you set the hysteresis to -24 dB, and the main threshold is at -12 dB, a signal greater than or equal to -12 dB will trigger the gate to begin opening. At that point, the gate will not begin closing until after the signal drops to a level equal to or lower than -24 dB. This helps to prevent the aforementioned “chatter,” because the gate isn’t constantly trying to follow a signal that’s varying quickly around a single detection point. The gate can be aggressive about opening, but “lazy” about closing.

Available hysteresis still isn’t enough for me to become a big fan of gating, but it does make these processors a bit more intelligent and flexible.