Audio Spectrum
A live frequency spectrum of incoming audio, for checking levels and designing audio-reactive effects.
The Audio Spectrum panel shows a live frequency spectrum of the incoming audio. Use it to check the audio input, spot hum or clipping, and find the frequency bands an audio-reactive effect should respond to.
Related concept: Beat time.
What it shows
The canvas draws 128 log-spaced bands from 20 Hz to 20 kHz. The X axis is logarithmic, so an octave takes the same screen width at any pitch. Labeled tick marks appear at 20, 50, 100, 200, 500, 1 k, 2 k, 5 k, 10 k, and 20 k Hz.
Bar height follows loudness the way you hear it. The scale is in decibels and spans 48 dB from the bottom of the panel to the top. A sound half as tall is thus 24 dB quieter, not half the amplitude. The scale also rises 3 dB per octave towards the high end, because music carries less energy the higher you go. Hi-hats and claps that sound as loud as the kick stand about as tall as it. Each bar counts all the energy inside its band and takes the peak across it, so short transients still reach the bar height.
Audio nodes read these same values, so a bar at half height is a node output of 0.5.
Enabling audio input
The panel draws nothing until the audio input runs. To start the input:
- Open Edit > Inputs > Audio.
- Pick a device.
- Turn on Audio-reactive effects.
Auto Beat-Sync also starts the input. The panel draws as soon as samples arrive. See Audio Input Dialog.
Using it with effects
Audio-reactive effect nodes, such as Audio Bands, Audio Level, Audio Spectrum, and Audio Peak, sample the same data shown here. To design an effect:
- Open the Audio Spectrum panel next to the Node Editor.
- Play the music you expect the effect to run against.
- Watch which band range lights up for the part of the music you want to follow. Kick drums sit around 50-100 Hz, snares and claps around 200-500 Hz, and hats above 4 kHz.
- Use an Audio Spectrum Range or Audio Bands node in the Node Editor with those frequency bounds.