What's A Gate?
A gadget that only lets certain sounds through — geddit? Deeper analysis on page 20.
Martin Sheehan follows the recording code and shuts them behind him.
I STOOD breathless before the Gate, its Threshold too high to overcome alone. I would hold fire until sufficient of our number had amassed in order that we might challenge this obstacle as one. Our number grew steadily until, under the weight of our purpose, the Gate suddenly flew open. Its Attack was obviously set fast. We piled through not yet knowing for how long we might be allowed to pass. It became apparent that a touch of Hold and a long Pause were set. As we thrust ever forward I chanced to glance abaft. A fleeting glimpse it was, but enough to lift the heart as I saw the last of our number squeeze through the Gate before it slid shut in the faces of our pursuers. I wondered, had we seen the last of these Hissmen.
Of course noise gates, or just simply gates as they are more commonly referred to now, do not merely shut out noise and hiss. The dropping of the word 'noise' and the development of the technique of 'gating' and are indication of the creative as well as the corrective purposes to which gates can be put.
The knobs to which any gate may subject you are as follows:
THRESHOLD: the level above which a gate will open.
ATTACK: the time it takes for the gate to open after the threshold has been crossed.
RELEASE: the time taken for the gate to close after the signal falls below the threshold.
HOLD: a period for which the gate will still stay open after the signal has dropped below the threshold, before the release is instigated.
DEPTH/FLOOR/ATTENUATION: the level to which the signal is dropped below the threshold, or in other words, how tightly the gate is shut and whether or not it is double glazed or uses draught excluder.
KEY/TRIGGER: a switch that will allow the gate to be opened and closed by a signal other than that being treated.
Some typical ranges over which the aforementioned parameters can be adjusted may be as follows:
Threshold: a 60dB range anywhere between +20 and -60dB.
Attack: 10 microseconds to 250 milliseconds.
Release: 10 milliseconds to 10 seconds.
Hold: 20 milliseconds to 2 seconds.
Attenuation: 0 to -7dB.
A gate can only remove noise effectively if there is sufficient distinction in level between the wanted signal and the nasty stuff. The reason for this is that the gate can make no equalitative distinction between the dying vibrations of your best bit of finger wobbling sustain ever and the buzz from the earth loop between your amp and echo unit. It decides when to shut down purely on the basis of level, and if the finger wobble dips below the buzz then tough. Fortunately, most people would fix the earth loop then adjust the threshold of the gate to a point just below their smallest wobble. Any fizz from a fuzz-box (sorry, overdrive pedal) or effects further back in the chain will then be shut out during the nonplaying periods. The noise is still there during the playing periods, but the playing should mask it.
The need for a variable threshold range is easy to explain as there are obviously going to be differences in level between wanted and unwanted signals for all instruments and sounds both live and in the studio. Not so obvious may be the requirement for Attack and Release times.
The primary objective of the attack time is to open quickly enough not to chop off the beginning of any sound. Laziness is not on. Too quickly, however, and an audible click may be generated. Percussive sounds will require the fastest attack settings and in some cases can tolerate and mask a slight click. Vocals, strings and wind instruments will generally require a more gently opened gate. The release timing also needs to be adjusted to suit the sound involved. A gate closing too quickly on a cymbal might turn a crash into a hi-hat or a subtly quivering vocal may be clipped off before its time. Conversely, an artificially clipped ending may be just what is called for in keeping a snare sounding tight, or to keep a kick drum from flapping.
The creative uses of a gate come into their own with the use of the key input facility. When a bass is fed through a gate being "opened" by a signal from the kick drum, a tight rhythm section can be contrived. A lead vocal can be used to trigger the harmony vocals and thus circumvent any stragglers. With the attenuation control set to just a few dBs, a legato keyboard part can be brought to life by having a rhythm guitar shoved up its key input. The various combinations of use are long as your ability to concentrate, but we cannot leave this topic without mentioning the names of Peter Gabriel and Hugh Padgham. These fine fellows were responsible for the advent and popularisation of that audio epidemic known as "gated reverb".
To achieve this thunderous effect, noise gates are patched into the reverb returns and are keyed by a feed from the drum they are treating. Fast attack and release times are selected and the length of the burst is set (popularly at around 300mS) by the hold control. Some digital reverbs can be programmed to gate themselves but, had it not been for Peter Gabriel and his gates, where would disco music be now?
Banishing all thoughts of the Hissmen from our minds we strode valiantly forward, but for what? Would the weight of compression bear down upon us? Would some of our number be filtered out, shelved off or notched up? Or perhaps — my heart raced — maybe we would feel that tingle of Excitement?!
Feature by Martin Sheehan
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