var source = null; function onload() { var engine = new jWebAudio.SoundEngine(); source = engine.addSoundSource({ 'url': 'resource/a.ogg' }); source.sound.load(function() { source.play(); }); } var useEffect = false; var id = null; function toggleEffect() { useEffect = !useEffect; if (useEffect) { id = source.sound.addEffect('telephonize'); } else if (id !== null) { source.sound.deleteEffect(id); } }