procedure playfreq(freq, volume: double);
var
  ctx: TJSAudioContext;
  buf: TJSAudioBuffer;
  wave: TJSFloat32Array;
  i,len: integer;
  src: TJSAudioBufferSourceNode;
  sampleFreq: double;

begin
  // connect to the browser window Audio Context. 
  asm
    ctx = new (window.AudioContext || window.webkitAudioContext)();
  end;

  // get the sample frequency the audio context can use 
  len := round(ctx.sampleRate);

  // create a new buffer of floating point values
  wave := TJSFloat32Array.new(len);

  // determine the sine wave frequency in relation to the audio context sample frequency
  sampleFreq := ctx.sampleRate / freq;

  // create a buffer on the audio context
  buf := ctx.createBuffer(1, len, ctx.sampleRate);
  wave := buf.getChannelData(0);

  // fill the float array with the sine wave data taking frequency & volume in account
  for i := 0 to len - 1 do
    wave[i] := (volume /100) * sin(i/(samplefreq/(2*PI)));

  // create a buffer source object for the audio contect
  src := ctx.createBufferSource();

  // assign the buffer holding the wave to the audio buffer source object
  src.buffer := buf;

  // connect the audio buffer source object to the audio context output
  src.connect(ctx.destination);

  // play the sample from position 0
  src.start(0.0);
end;