How to play ultrasonic WAV/PCM file in javascript without losing data

Question

I need to loop an audio file (WAV, OGG or raw PCM) in the browser that contains segments which are unheard (ultrasonic) by the human ear (yet contain data which is valuable to me).

Using Chrome on Mac, I've noticed that if the segments of unheard sound are relatively short, I get all the data back (heard + unheard). In contrast, if the segments of unheard sound are longer than a certain threshold, it will fade out the whole channel quickly and effectively cancel the rest of the file completely, until the next loop cycle begins.

The way I'm loading and playing the sound is like so:

var b = msg.data; // binary msg received from websocket
b.type = "audio/wav";
var URLObject = window.webkitURL || window.URL;
var url = URLObject.createObjectURL(b);
var snd = document.createElement("audio");
snd.setAttribute("src", url);
snd.addEventListener("loadeddata", function() {
    snd.loop = true;
    snd.muted = false;
    snd.play();
});

I'm looking for a way to cancel this automatic filtering of unheard sounds. Eventually, I would like a way to do this cross-browser. If not possible using JavaScript, a Flash solution will also be accepted.

Sample ultrasonic WAV files (~1MB each): https://drive.google.com/file/d/0B5sMkxczD6sNbm04MmxMTmIwdlk/edit?usp=sharing

https://drive.google.com/file/d/0B5sMkxczD6sNal91WUhRNWo2d3c/edit?usp=sharing

Answer 1

There isn't a single approach that will work on all browsers, unfortunately. For most browsers on the desktop and iOS too you can use the Web Audio API as shown here:

http://www.html5rocks.com/en/tutorials/webaudio/intro/

For IE/Android you need to use Flash to play a WAV/PCM, or play OGG with HTML5 Audio tag, but the latter may lose the ultrasonic frequencies.

So in general, you need to write code that will check what the current browser supports and use that, starting with Web Audio API, then trying HTML5 Audio, then Flash.