signaltohertz

calculate Hertz frequency from audio buffer. Nothing more nothing less.

// include library
var sig2hz = require('signaltohertz');

// input an array with frequencies.
var hertz = sig2hz(frequencyArray);

// input an array with frequencies and add a rate that
// if yours is different to the defaults.
var hertz = sig2hz(frequencyArray, {
    rate: 0.5
    });

You can use it with the WebAudioContext like so:

var audio, volume, frequencies, frequency, audioContext, analyser, 
    microphone, waveform, amplitude;
navigator.getUserMedia(
    {audio: true, video: false},
    function (stream) {
    audioContext = new AudioContext();
    analyser = audioContext.createAnalyser();
    frequencies = new Float32Array(analyser.frequencyBinCount);
    console.log(analyser)
    amplitude = new Uint8Array(analyser.frequencyBinCount);

    volume = audioContext.createGain();

    microphone = audioContext.createMediaStreamSource(stream);
    microphone.connect(volume);
    microphone.connect(analyser);

    renderFrame();
  }, function (error) { console.log(error)};

  function renderFrame () {
      setTimeout(requestAnimationFrame(renderFrame), 100);
      analyser.getFloatFrequencyData(frequencies);
      analyser.getByteTimeDomainData(amplitude);

      frequency = signaltohertz(frequencies);
      console.log(frequency);
    };