CODEWITHSUNDEEP
javascriptaudioweb-audio-apifrequency-analysis
Max
Max

Reputation: 3

Mapping frequencies to loudness using the Web Audio API

I want to detect played notes and chords using the Web Audio API (using the microphone as an input device). Before I can analyse the data, I need it the individual frequencies mapped to their loudness. I started with the following snippet:

const stream = await navigator.mediaDevices.getUserMedia({
    audio: true,
    video: false
});
const context = new AudioContext();
const source = context.createMediaStreamSource(stream);
const analyser = context.createAnalyser();

const data = new Uint8Array(analyser.frequencyBinCount);
analyser.getByteFrequencyData(data);

data now is an array of values between 0 to 255. The question I have now is how can I map the frequencies to the loudness values of the data array?

Ideally, I'd like an object like this:

{
    ...
    438: 128,
    439: 200,
    440: 255,
    441: 200,
    ...
}

Thanks for your help.

Upvotes: 0

Views: 290

Answers (1)

Raymond Toy
Raymond Toy

Reputation: 6048

The value in data[k] corresponds to the frequency k * Nyquist/frequencyBinCount where Nyquist is one half of the sampling frequency, AudioContext.sampleRate.

I think that's what you're asking for. If not please clarify.

Upvotes: 0

Related Questions