Do you find it difficult to take out that annoying hissing sound from your tracks? Looking for the right signal processor to solve the problem? Many audio engineers and musicians deal with noise issues when working with music and sound in general. If you aim to have a much cleaner mix for your projects, then you must ask – What is a Noise Gate?
Just like other articles, we will go through the various aspects surrounding the subject that we are discussing today, which is the noise gate. Learn about the fundamental design principle that drives this audio signal processor. Familiarise yourself with the various parameters on the noise gate that are used to attenuate audio signals. Ready to learn? Then, let’s begin!
Introduction – What does it do?
Sometimes just called “gate”, a noise gate is essentially an electronic device or software (used in DAWs) that functions to attenuate an audio signal’s volume. Unlike an audio signal compressor, which attenuates signals that goes above a threshold (set by the operator), noise gates attenuate signals that fall below the set threshold.
Take note that noise gates only attenuate signals by an amount that is pre-determined (referred to as range). The most basic noise gate designs, will only allow a signal to pass through, if it goes beyond a set threshold (meaning the gate is ‘open’). Any signal that falls under the set threshold, will either not be able to pass or be substantially attenuated (meaning the gate is ‘closed’).
Simply put, if the “clean” signal’s level is above the “noise” level, the noise gate will be used. By setting the threshold to be above the level of the “noise”, the gate will close when there is no “signal”. Noise gates do not take out noise from the signal, and both the signal with the noise will pass if the gate is opened. Basic parameters include ‘attack’, ‘release’, and ‘hold’ settings and may feature a ‘look-ahead’ function.
Let us now look at the two topics of discussion:
- Primary uses
- Audio noise reduction
Noise gates are often utilised in recording studios and live sound reinforcement systems. Musicians also use portable stand-alone units to reduce undesirable noise from their amplification systems. Noise gates can also be “band-limited” in order to eliminate specific frequency bands that contain only static. This is useful in eliminating background noise from audio tracks.
In the following section, we will take a deeper look into the various parameters of a noise gate:
The threshold parameter on the noise gate is the most fundamental feature that will be found on all noise gate units, both hardware and software versions. It is used to determine the level at which the gate will open. More advanced noise gates may have extended features.
Most noise gate units today (especially in software versions used in DAWs), feature the attack parameter. The Attack control allows the user to set the time that will be taken for the gate to switch from closed to open, very similar to a fade-in effect.
Release sets the time the gate will take to fully close after being opened. Fast release times will cut off the sound sharply, if it falls below the threshold. Slower release times allows for a smooth change from open to closed, akin to a slow fade out. A “click” can sometimes be heard when the gate re-opens, if the release time is too short. After threshold, release is the most common control on noise gates.
The Hold control is a very useful feature that allows the user to determine how long the gate will stay open after the signal falls below the set threshold. This parameter is often found to be very effectively applied during short pauses between words or sentences within a recorded speech signal.
When the gate is closed, the level of attenuation that is being applied on the signal can be adjusted by the Range parameter. For most audio applications, a complete attenuation will take effect, meaning no signal will pass when the gate is closed. However, under certain situations, a complete attenuation is not always wanted and can be altered through the range control.
External sidechain can be found on advanced gates. This allows another audio signal to trigger the gate via an additional input. Electronic music productions use a variation of a sidechained noise gate called trancegate or just simply gate. A trancegate is controlled by a pre-programmed pattern (not an audio signal) resulting in an accurately controlled chopping of a sustained sound.
Hysteresis is often implemented by most noise gates, meaning that they have two thresholds – one to open the gate and another, set a few dB below, to close the gate. Once an audio signal drops below the close threshold, it then has to rise higher to reach the open threshold for the gate to open. Hence, the signal that consistently crosses over the close threshold, will not trigger the gate to open and cause chattering. Setting a longer hold time will also help prevent chattering, as described above.
Audio Noise Reduction
Noise gates are often used in audio post processing, to minimise steady noise sources such as low-frequency rumbling sounds from LP records, high-frequency hissing sounds from audio tape, static interference from a radio or amplifier, and hum from a power system, without drastically reducing the quality of the source sound.
Audio signals (like music or speech) will go through a series of overlapping band-pass filters, which will then break up the signal into many frequency bands. If the amplitude of the signal (in any of the band-pass filters) drops below a preset threshold, then that band will be filtered out from the final sound.
This method of using a noise gate helps to greatly reduce audible background noise, as only the affected frequency components of the noise that are within the gated pass-bands survive.
We have come to the end of this article folks. I hope you people now have a better understanding of noise gates, and are able to use it in your music projects!
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