files/en-us/web/api/convolvernode/buffer/index.md
{{ APIRef("Web Audio API") }}
The buffer property of the {{ domxref("ConvolverNode") }} interface represents a mono, stereo, or 4-channel {{domxref("AudioBuffer")}} containing the (possibly multichannel) impulse response used by the ConvolverNode to create the reverb effect.
This is normally a simple recording of as-close-to-an-impulse as can be found in the space you want to model. For example, if you want to model the reverb in your bathroom, you might set up a microphone near the door to record the sound of a balloon pop or synthesized impulse from the sink. That audio recording could then be used as the buffer.
This audio buffer must have the same sample-rate as the AudioContext or an exception will be thrown. At the time when this attribute is set, the buffer and the state of the attribute will be used to configure the ConvolverNode with this impulse response having the given normalization. The initial value of this attribute is null.
An {{domxref("AudioBuffer")}}.
The following example creates a convolver node and assigns it an {{domxref("AudioBuffer")}}.
For more complete applied examples/information, check out our Voice-change-O-matic demo (see app.js for the code that is excerpted below).
const audioCtx = new AudioContext();
// …
const convolver = audioCtx.createConvolver();
// …
// Grab audio track via fetch() for convolver node
try {
const response = await fetch(
"https://mdn.github.io/voice-change-o-matic/audio/concert-crowd.ogg",
);
const arrayBuffer = await response.arrayBuffer();
const decodedAudio = await audioCtx.decodeAudioData(arrayBuffer);
convolver.buffer = decodedAudio;
} catch (error) {
console.error(
`Unable to fetch the audio file: ${name} Error: ${err.message}`,
);
}
{{Specifications}}
{{Compat}}