audio spectrum code

gistfile1.cs

using UnityEngine;
using System.Collections;

/// <summary>
/// A class for taking spectrum data & calculating the volume of various frequency bands.
/// 
/// Notes:
/// This doesn't do any smoothing, so wherever you leverage these values you'll probably want to do something.
/// In my project I immediately jump to any higher value, and then have it decay over time at a fixed rate.
/// </summary>

public class SpectrumAnalyzer : MonoBehaviour {

    // The audio source to grab spectrum data from. Probably your music track
    public AudioSource Source;
    
    // Audio channel to use, I think 0 is left channel and 1 is right channel?
    public int Channel = 0;
    
    // Number of samples to take, a high value here is usually a good idea. I use 1024 by default
    public int NumSamples = 1024;

    // Each vector in this array describes the frequency bands you want to track, in my project I use:
    // 20 - 31.5
    // 31.5 - 63
    // 63 - 125
    // 125 - 250
    // 250 - 800
    // 800 - 2000
    // 2000 - 3500
    // 3500 - 6000
    // 6000 - 12000
    // 12000 - 23000
    public Vector2[] Bands;
    
    // The volume of each band - should be between 0 & 1. Updated each frame.
    public float[] BandVolumes;

    // The average volume of all bands
    public float AverageVolume;

    float _fMax;
    float[] _samples;

    public int NumBands
    {
        get
        {
            return Bands.Length;
        }
    }

    void Start()
    {
        _samples = new float[NumSamples];
        BandVolumes = new float[NumBands];
        _fMax = AudioSettings.outputSampleRate / 2.0f;
    }

    void Update()
    {
        Source.GetSpectrumData(_samples, 0, FFTWindow.BlackmanHarris);

        AverageVolume = 0;
        for (var i = 0; i < NumBands; i++)
        {
            var band = Bands[i];

            var n1 = Mathf.FloorToInt(band.x * NumSamples / _fMax);
            var n2 = Mathf.FloorToInt(band.y * NumSamples / _fMax);
            float sum = 0;

            for (var f = n1; f <= n2; f++)
            {
                sum += _samples[f];
            }

            BandVolumes[i] = sum;
            AverageVolume += sum;
        }

        AverageVolume /= BandVolumes.Length;
    }
}

Awesome!
Thank you