var button = document.querySelector("button");

button.onclick = function(e) {

  button.disabled = true;

  var context = new AudioContext();

  var currentTime = context.currentTime;

  var osc = context.createOscillator();

  osc.type = "square";

  osc.frequency.value = 20.0;

  osc.frequency.setValueAtTime( 20.0, currentTime );

  osc.frequency.exponentialRampToValueAtTime( 20000.0, currentTime + 10.0 );

  osc.start(currentTime);

  osc.stop(currentTime + 10.0);

  osc.connect( context.destination );

  osc.onended = function(evt) {

    button.disabled = false;

  };

};