Beep according to the realtime visitor count on Google Analytics

ga-realtime-visitorcount-beeper.js

/*
  This is more a simple and naive proof of concept than anything
  it's based on [this answer](https://stackoverflow.com/a/41077092/1358317)
  on stackoverflow.
*/

(function() {  
  // Create the audio context
  var audioCtx = new(window.AudioContext || window.webkitAudioContext)();

  function beep(options, callback) {
    options = options || {};
    var volume = options.volume || 1;
    var frequency = options.frequency || 196;
    var type = options.type || 'sine';
    var duration = options.duration || 500;
    var delay = options.delay || 0;
    var harsh = options.harsh || false;

    setTimeout(function() {
      var oscillator = audioCtx.createOscillator();
      var gainNode = audioCtx.createGain();

      oscillator.connect(gainNode);
      gainNode.connect(audioCtx.destination);

      oscillator.frequency.value = frequency;
      oscillator.type = type;
      if (callback){
        oscillator.onended = callback;
      }
      
      if (harsh) {
        gainNode.gain.value = volume;
      } else {
        gainNode.gain.value = 0.00001;
        gainNode.gain.setTargetAtTime(volume, audioCtx.currentTime, duration / 1000);
        gainNode.gain.setTargetAtTime(0.00001, audioCtx.currentTime + (duration / 4) / 1000, duration / 4 / 1000);
      }
      oscillator.start();

      setTimeout(
        function() {
          oscillator.stop();
        },
        duration
      );
    }, (delay ? delay : 0));
  }

  function handleTick() {
    // 196 Hz is the frequency for a G3
    // see https://www.seventhstring.com/resources/notefrequencies.html
    var baseFreq = 196;
    var beepDelay = 750;
    
    var nbVisitors = document.getElementById('ID-overviewCounterValue').innerText;

    // Log the current visitor count if not 0 and beep accordingly
    if( nbVisitors != 0) {
      console.log(
        new Date().toLocaleString() + "\t",
        nbVisitors + ' visitor' + (nbVisitors > 1 ? 's' : '')
      );
      
      for(var i = 0; i < nbVisitors; i++) {
        // 4 / 3 is the ratio for a perfect fourth, so it'll always sound nice
        // see http://www.sengpielaudio.com/Root-Ratios.gif
        beep({
          frequency: baseFreq,
          delay: i * beepDelay
        });
        beep({
          frequency: baseFreq * 4 / 3,
          delay: i * beepDelay + 150
        });
        beep({
          frequency: baseFreq * 4 / 3 * 4 / 3,
          delay: i * beepDelay + 150 * 2
        });
      }
    }
  }

  // Call the handler immediatly, before setting an interval
  handleTick();

  // Change the interval to whatever you like
  // Google analytics stops counting a user as active after 5 minutes
  window.setInterval(handleTick, 5 * 60 * 1000);
})()

Notes frequencies:

N°	C	C#	D	Eb	E	F	F#	G	G#	A	Bb	B
0	16.35	17.32	18.35	19.45	20.60	21.83	23.12	24.50	25.96	27.50	29.14	30.87
1	32.70	34.65	36.71	38.89	41.20	43.65	46.25	49.00	51.91	55.00	58.27	61.74
2	65.41	69.30	73.42	77.78	82.41	87.31	92.50	98.00	103.8	110.0	116.5	123.5
3	130.8	138.6	146.8	155.6	164.8	174.6	185.0	196.0	207.7	220.0	233.1	246.9
4	261.6	277.2	293.7	311.1	329.6	349.2	370.0	392.0	415.3	440.0	466.2	493.9
5	523.3	554.4	587.3	622.3	659.3	698.5	740.0	784.0	830.6	880.0	932.3	987.8
6	1047	1109	1175	1245	1319	1397	1480	1568	1661	1760	1865	1976
7	2093	2217	2349	2489	2637	2794	2960	3136	3322	3520	3729	3951
8	4186	4435	4699	4978	5274	5588	5920	6272	6645	7040	7459	7902

source

Interval ratios

source