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Audio effects

Godot includes several audio effects that can be added to an audio bus to alter every sound file that goes through that bus.

../../_images/audio_buses4.png

Try them all out to get a sense of how they alter sound. Here follows a short description of the available effects:

Amplify

Amplify changes the volume of the signal. Some care needs to be taken, though: setting the level too high can make the sound digitally clip, which can produce unpleasant crackles and pops.

BandLimit and BandPass

These are resonant filters which block frequencies around the Cutoff point. BandPass can be used to simulate sound passing through an old telephone line or megaphone. Modulating the BandPass frequency can simulate the sound of a wah-wah guitar pedal, think of the guitar in Jimi Hendrix's Voodoo Child (Slight Return).

Capture

The Capture effect copies the audio frames of the audio bus that it is on into an internal buffer. This can be used to capture data from the microphone or to transmit audio over the network in real-time.

Chorus

As the name of the effect implies, the Chorus effect makes a single audio sample sound like an entire chorus. It does this by duplicating a signal and very slightly altering the timing and pitch of each duplicate, and varying that over time via an LFO (low frequency oscillator). The duplicate(s) are then mixed back together with the original signal, producing a lush, wide, and large sound. Although chorus is traditionally used for voices, it can be desirable with almost any type of sound.

Compressor

A dynamic range compressor automatically attenuates (ducks) the level of the incoming signal when its amplitude exceeds a certain threshold. The level of attenuation applied is proportional to how far the incoming audio exceeds the threshold. The compressor's Ratio parameter controls the degree of attenuation. One of the main uses of a compressor is to reduce the dynamic range of signals with very loud and quiet parts. Reducing the dynamic range of a signal can make it fit more comfortably in a mix.

The compressor has many uses. For example:

  • It can be used in the Master bus to compress the whole output prior to being hit by a limiter, making the effect of the limiter much more subtle.

  • It can be used in voice channels to ensure they sound as even as possible.

  • It can be sidechained by another sound source. This means it can reduce the sound level of one signal using the level of another audio bus for threshold detection. This technique is very common in video game mixing to "duck" the level of music or sound effects when in-game or multiplayer voices need to be fully audible.

  • It can accentuate transients by using a slower attack. This can make sound effects more punchy.

Note

If your goal is to prevent a signal from exceeding a given amplitude altogether, rather than to reduce the dynamic range of the signal, a limiter is likely a better choice than a compressor for this purpose. However, applying compression before a limiter is still good practice.

Delay

Digital delay essentially duplicates a signal and repeats it at a specified speed with a volume level that decays for each repeat. Delay is great for simulating the acoustic space of a canyon or large room, where sound bounces have a lot of delay between their repeats. This is in contrast to reverb, which has a more natural and blurred sound to it. Using this in conjunction with reverb can create very natural sounding environments!

Distortion

Makes the sound distorted. Godot offers several types of distortion:

  • Overdrive sounds like a guitar distortion pedal or megaphone. Sounds distorted with this sound like they're coming through a low-quality speaker or device.

  • Tan sounds like another interesting flavor of overdrive.

  • Bit crushing clamps the amplitude of the signal, making it sound flat and crunchy.

All three types of distortion can add higher frequency sounds to an original sound, making it stand out better in a mix.

EQ

EQ is what all other equalizers inherit from. It can be extended with Custom scripts to create an equalizer with a custom number of bands.

EQ6, EQ10, EQ21

Godot provides three equalizers with different numbers of bands, which are represented in the title (6, 10, and 21 bands, respectively). An equalizer on the Master bus can be useful for cutting low and high frequencies that the device's speakers can't reproduce well. For example, phone or tablet speakers usually don't reproduce low frequency sounds well, and could make a limiter or compressor attenuate sounds that aren't even audible to the user anyway.

Note: The equalizer effect can be disabled when headphones are plugged in, giving the user the best of both worlds.

Filter

Filter is what all other filters inherit from and should not be used directly.

HighPassFilter

Cuts frequencies below a specific Cutoff frequency. HighPassFilter is used to reduce the bass content of a signal.

HighShelfFilter

Reduces all frequencies above a specific Cutoff frequency.

Limiter

A limiter is similar to a compressor, but it's less flexible and desi