Audio Effects – Noise Gate & Flange

September 6, 2006

Continuing the audio effects series, again, we all know of audio effects and what they generally are supposed to do. They are used to manipulate audio in ways that are not available with traditional playing and recording techniques. If you’re like me, and enjoy dabbling in audio production, you’re probably familiar with all the basic effects and maybe some other types. Noise gate will be one of the topics of discussion today. Noise gate, what the heck is that? If that was your first reaction, you’re not alone. Please don’t worry; we will be demystifying this subject later on in the article. We will also be discussing flange, which is a more standard and widely used audio effect. So, in today’s article we will be discussing both noise gate and flange effects, how they work and why they work the way they do.  

Noise GateBasically, noise gate is a device or software logic that is used to manage the volume of an audio signal, in recording studios and in sound reinforcement. They are also used by musicians, in a portable form, to control amplification noise. At its most simple form it controls noise by only allowing sound to pass through it at a certain set threshold. Think of it as a literal gate; when the gate is open sound can pass, when the gate is closed no signal is allowed through. More robust noise gate units have extra controls, I.E. attack, sustain, decay, release. This is so that you can further control the gating of your audio. Say you’d like to have the gate applied in a hard fashion, you would set a short attack and a short release, so on and so forth. Noise gates are often used to isolate background noise from live recordings in order to eliminate them from the final copy. 

FlangeFlange is related to the phasing effect produced by a, well, phaser effects unit. It is produced when two identical signals are mixed together, with one of the signals time-delayed by a small and gradually changing amount. The amount is usually equal to or less than 20 milliseconds. Peaks and notches are produced in the combined frequency spectrum, related in a linear harmonic series. Part of the output signal is fed back in and resonates, intensifying the peaks and notches. This effect was originally generated with 3 three headed tape machines. Two of the tape machines would play the signal, obviously somewhat out of sync, and the third tape machine would record the output. The modern version of the effect is created using DSP (digital signal processing) technology. 

This is the second part in my continuing series on audio effects. Today we discussed noise gate and flange, we’ll be moving on some more advanced effects later on. I hope that this helped you all understand the basic functionality of these two effects, ultimately making your next foray into audio editing a bit less intimidating.  

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