Audacity is not able to apply effects in real time while recording, but this plug-in provides an equivalent to AGC (Automatic Gain Control) when applied after recording.
The effect is similar to the AGC found on pocket recorders, camcorders and similar devices.
Note: It does not repair clipped audio. The original recording level still needs to be below 0 dB. What it does is to dynamically bring the recorded level up to 0 dB.
AGC Strength: [0 to 100 %. Default 100 %] How much effect is applied. At 0% there is no effect.
Gain reaction speed: [0.5 to 10 seconds. Default 1.5] How quickly the gain reacts to changes in volume level.
Audio source filter: [Options: Music, Voice, Telephone. Default “Music”] Pre-filters the audio to reduce low rumble and high hiss. The “Music” setting is unfiltered (full spectrum).
Squelch threshold level: [-60 to -6 dB. Default -60 dB] Level at which “Squelch” is activated (see notes below).
Squelch attenuation: [-30 to 0 dB Default 0 dB] How much sound below the squelch threshold is attenuated (see notes below).
Difference between this effect and a “Dynamics Compressor”:
- The default settings are far more “aggressive” than you will find on most “compressor” effects.
- Rather than pushing down the level of the loud parts, this effect pushes up the level of the quiet parts. Even though a conventional compressor may apply “make up gain”, the overall effect is still not quite the same.
- Typically a dynamics compressor will mostly affect peaks that are above a fairly high threshold, thus there is a lot more “effect” on loud parts than on quiet parts. This AGC plug-in affects all audio that is above a fairly low threshold, thus there is more “effect” on quiet parts than on loud parts.
For evening out the level of multiple people talking, some loudly and some quietly, try a short “Gain reaction speed” of around 0.5 seconds.
For classical music, try a slow “Gain reaction speed”, say around 6 seconds, and turn down to AGC strength (try around 50%).
Squelch: “Noise Squelch” is a feature that is commonly found on walkie talkie radios to reduce or mute the noise level when no-one is talking. This plug-in includes two “Squelch” controls.
Squelch threshold level sets the level below which the “squelch” is activated. The default level is -60 dB, which is suitable for a high quality recording. For recordings that have a higher background noise level, best results will be achieved by increasing this control. If it is set too high it will prevent quiet sounds from being automatically amplified.
Squelch attenuation sets how strongly noise below the squelch threshold is muted. The default is 0 dB which does not “mute” audio below the threshold, but just limits how much it is amplified. For a stronger “noise gate” type effect, try moving this slider to the (-30 dB) minimum.
One problem that is inherent with AGC effects is that when the input goes quiet, the background noise level may be drastically boosted. To reduce this unwanted effect, increase the “Squelch” threshold (if necessary). Sound below the squelch threshold will be boosted less than audio above the threshold.
If, when applied to a voice recording, some quiet voices are not being amplified, then either the Gain reaction speed is set too slow (try reducing it to 0.5 seconds) or the Squelch level is set too high.
Audio Source Filter
When set to “Music” there is no pre-filtering.
The “Voice” setting will filter out low booms, pops and rumbles, and high hiss before applying the automatic gain effect. This setting is recommended for voice recordings.
The “telephone” setting reduces more low and more high frequencies than the “Voice” filter. On high quality speech recordings it will probably remove too much, making voices sound “thin” and a bit “muffled”. For low quality voice recordings it can help to reduce a lot of unwanted noise. This setting is recommended for telephone and other low quality voice recordings.
agc.ny (2.45 KB)
Latest Version of Automatic Gain Control.
Please read the additional notes in this post: https://forum.audacityteam.org/viewtopic.php?p=337691#p337691