audio-analysis

Audio Analysis

FFT, frequency extraction, and audio data analysis.

Quick Start

import * as Tone from 'tone';

// Create analyzer
const analyser = new Tone.Analyser('fft', 256);
const player = new Tone.Player('/audio/music.mp3');

player.connect(analyser);
player.toDestination();

// Get frequency data
const frequencyData = analyser.getValue(); // Float32Array

Analyzer Types

FFT Analyzer

// FFT (Fast Fourier Transform) - frequency spectrum
const fftAnalyser = new Tone.Analyser({
  type: 'fft',
  size: 256,        // Must be power of 2: 32, 64, 128, 256, 512, 1024, 2048
  smoothing: 0.8    // 0-1, higher = smoother transitions
});

// Returns Float32Array of dB values (typically -100 to 0)
const fftData = fftAnalyser.getValue();

Waveform Analyzer

// Waveform - time domain data
const waveformAnalyser = new Tone.Analyser({
  type: 'waveform',
  size: 1024
});

// Returns Float32Array of amplitude values (-1 to 1)
const waveformData = waveformAnalyser.getValue();

Meter (Volume Level)

// Meter - overall volume level
const meter = new Tone.Meter({
  smoothing: 0.9,
  normalRange: false  // true for 0-1, false for dB
});

player.connect(meter);

// Get current level
const level = meter.getValue(); // dB or 0-1

FFT Size Impact

Size	Frequency Resolution	Time Resolution	Use Case
32	Low	High	Beat detection
128	Medium	Medium	General visualization
256	Good	Good	Balanced (default)
1024	High	Low	Detailed spectrum
2048	Very High	Very Low	Audio analysis tools

Frequency Bands

Manual Band Extraction

const analyser = new Tone.Analyser('fft', 256);

function getFrequencyBands() {
  const data = analyser.getValue();
  const binCount = data.length;

  // Define frequency band ranges (approximate for 44.1kHz sample rate)
  // Each bin = (sampleRate / 2) / binCount Hz
  const bands = {
    sub: average(data, 0, Math.floor(binCount * 0.03)),      // ~20-60 Hz
    bass: average(data, Math.floor(binCount * 0.03), Math.floor(binCount * 0.08)),  // ~60-250 Hz
    lowMid: average(data, Math.floor(binCount * 0.08), Math.floor(binCount * 0.15)), // ~250-500 Hz
    mid: average(data, Math.floor(binCount * 0.15), Math.floor(binCount * 0.3)),     // ~500-2000 Hz
    highMid: average(data, Math.floor(binCount * 0.3), Math.floor(binCount * 0.5)),  // ~2000-4000 Hz
    high: average(data, Math.floor(binCount * 0.5), binCount)                         // ~4000+ Hz
  };

  return bands;
}

function average(data, start, end) {
  let sum = 0;
  for (let i = start; i < end; i++) {
    sum += data[i];
  }
  return sum / (end - start);
}