AudioBuffer

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

TheAudioBuffer interface represents a short audio asset residing in memory, created from an audio file using theAudioContext.decodeAudioData() method, or from raw data usingAudioContext.createBuffer(). Once put into an AudioBuffer, the audio can then be played by being passed into anAudioBufferSourceNode.

Objects of these types are designed to hold small audio snippets, typically less than 45 s. For longer sounds, objects implementing theMediaElementAudioSourceNode are more suitable. The buffer contains the audio signal waveform encoded as a series of amplitudes in the following format: non-interleaved IEEE754 32-bit linear PCM with a nominal range between-1 and+1, that is, a 32-bit floating point buffer, with each sample between -1.0 and 1.0. If theAudioBuffer has multiple channels, they are stored in separate buffers.

Constructor

AudioBuffer(): Creates and returns a newAudioBuffer object instance.

Instance properties

AudioBuffer.sampleRateRead only: Returns a float representing the sample rate, in samples per second, of the PCM data stored in the buffer.
AudioBuffer.lengthRead only: Returns an integer representing the length, in sample-frames, of the PCM data stored in the buffer.
AudioBuffer.durationRead only: Returns a double representing the duration, in seconds, of the PCM data stored in the buffer.
AudioBuffer.numberOfChannelsRead only: Returns an integer representing the number of discrete audio channels described by the PCM data stored in the buffer.

Instance methods

AudioBuffer.getChannelData(): Returns aFloat32Array containing the PCM data associated with the channel, defined by thechannel parameter (with0 representing the first channel).
AudioBuffer.copyFromChannel(): Copies the samples from the specified channel of theAudioBuffer to thedestination array.
AudioBuffer.copyToChannel(): Copies the samples to the specified channel of theAudioBuffer, from thesource array.

Example

The following simple example shows how to create anAudioBuffer and fill it with random white noise. You can find the full source code at ourwebaudio-examples repository; arunning live version is also available.

const audioCtx = new AudioContext();// Create an empty three-second stereo buffer at the sample rate of the AudioContextconst myArrayBuffer = audioCtx.createBuffer(  2,  audioCtx.sampleRate * 3,  audioCtx.sampleRate,);// Fill the buffer with white noise;// just random values between -1.0 and 1.0for (let channel = 0; channel < myArrayBuffer.numberOfChannels; channel++) {  // This gives us the actual array that contains the data  const nowBuffering = myArrayBuffer.getChannelData(channel);  for (let i = 0; i < myArrayBuffer.length; i++) {    // Math.random() is in [0; 1.0]    // audio needs to be in [-1.0; 1.0]    nowBuffering[i] = Math.random() * 2 - 1;  }}// Get an AudioBufferSourceNode.// This is the AudioNode to use when we want to play an AudioBufferconst source = audioCtx.createBufferSource();// set the buffer in the AudioBufferSourceNodesource.buffer = myArrayBuffer;// connect the AudioBufferSourceNode to the// destination so we can hear the soundsource.connect(audioCtx.destination);// start the source playingsource.start();