How to play a specific frequency with Javascript?

Question

I want a function that works like this:

playSound(345, 1000)

Which would play a tone of 345 hz for 1000 milliseconds. What is the simplest way to achieve this in JavaScript? I don't mind if it uses a sample (maybe of a sin wave, or piano), or uses the computer's hardware to generate the sound.

Answer 1

As already pointed out in the comments, the way to do it is through the OscillatorNode.

// create web audio api context
var audioCtx = new(window.AudioContext || window.webkitAudioContext)();

function playNote(frequency, duration) {
  // create Oscillator node
  var oscillator = audioCtx.createOscillator();

  oscillator.type = 'square';
  oscillator.frequency.value = frequency; // value in hertz
  oscillator.connect(audioCtx.destination);
  oscillator.start();

  setTimeout(
    function() {
      oscillator.stop();
      playMelody();
    }, duration);
}

function playMelody() {
  if (notes.length > 0) {
    note = notes.pop();
    playNote(note[0], 1000 * 256 / (note[1] * tempo));
  }
}

notes = [
  [659, 4],
  [659, 4],
  [659, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4],
  [0, 4],
  [987, 4],
  [987, 4],
  [987, 4],
  [1046, 8],
  [0, 16],
  [783, 16],
  [622, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4]
];

notes.reverse();
tempo = 100;

playMelody();