Final Cut Pro: What is a Expander or Noise Gate Filter

Expander and gate both are basically noise management equipment. The biggest enemy of a recording process is unwanted noise, which can be caused by the environment where the recording is being made, or can also be generated by the circuitry and storage medium used in the recording. This issue is magnified when a multi-track process because the noise on each track is added to the other noises from all the tracks. This generally means that the level of the noise can go past the comfortable level which could be annoying and ruin the entire track.

It is impossible to remove noise once it is part of the electrical signal, and if and when it is removed, the tone of the sound will probably be changed. So it is imperative to manage and if possible, totally eradicate the noise so that it will not reduce the quality of the track.

An expander amplifies the vibrant range of an acoustic signal through reduction of the audio signal when it descends to a certain threshold. This will result in a relatively quiet part of the audio signal even more proportionally quiet, so the variation between the muted and louder parts of the sound are increased.

An expander with a high percentage value is referred to as a noise gate and is utilized to make the sound below the audio threshold close to being as silent as possible. In contrast to a compressor, which influences the loud portions of the signal, an expander has an effect on the quiet segment of the signal. This is generally the reverse principle applied to compression. Expanders and noise gate controls are useful for bringing back the natural vibrancy of the sound.

Controls and Their Functions

  • Threshold Slider: Delineates how the lowest part of the clip could be before the expander settings are applied. This is the very first setting you will adjust.
  • Ratio Slider: This control lets a specific quantity of bleed from the original audio signal, even when the noise gate is closed. This control is useful when the editor wants to retain the ambiance of the track. This also influences the level of expansion applied to increase the signal.
  • Attack Time Slider: This control is less important than the others; however, it is still useful. The attack time slider is used to set the time for the gate to open fully after the audio level surpasses the threshold. If the gate opens quickly, the low frequency signals are distorted. This happens because the abrupt alteration could be applied through the cycle of frequency, which results to an audible clicking sound. If the attack time is too long, the results will have less impact.
  • Release Time Slider: This control is applied as resolution to cutting of low signal audio levels. This lets the sound editor set the time the filter releases the changes it made in the audio signal or the closing of the gate. This controls the noise from stopping suddenly, instead the audio level gradually fades.