index.md

---

title: AudioBuffer.numberOfChannels
slug: Web/API/AudioBuffer/numberOfChannels
page-type: web-api-instance-property
browser-compat: api.AudioBuffer.numberOfChannels

---

{{ APIRef("Web Audio API") }}

The numberOfChannels property of the {{ domxref("AudioBuffer") }} interface returns an integer representing the number of discrete audio channels described by the PCM data stored in the buffer.

Value

An integer.

Examples

// Stereo
const channels = 2;

// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
const frameCount = audioCtx.sampleRate * 2.0;
const myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate);

button.onclick = () => {
  // Fill the buffer with white noise;
  // just random values between -1.0 and 1.0
  for (let channel = 0; channel < channels; channel++) {
    // This gives us the actual ArrayBuffer that contains the data
    const nowBuffering = myArrayBuffer.getChannelData(channel);
    for (let i = 0; i < frameCount; i++) {
      // Math.random() is in [0; 1.0]
      // audio needs to be in [-1.0; 1.0]
      nowBuffering[i] = Math.random() * 2 - 1;
    }
  }

  console.log(myArrayBuffer.numberOfChannels);
};

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Using the Web Audio API