play .wav sound file encoded in base64 with javascript

That doesn't look like the correct way to use the Audio constructor for HTMLAudioElement / <audio>.

Slight adjustment

var snd = new Audio("data:audio/wav;base64," + base64string);
snd.play();

If it works in console but not in script, it may be getting garbage collected, in which case scope it so it will stay

var Sound = (function () {
    var df = document.createDocumentFragment();
    return function Sound(src) {
        var snd = new Audio(src);
        df.appendChild(snd); // keep in fragment until finished playing
        snd.addEventListener('ended', function () {df.removeChild(snd);});
        snd.play();
        return snd;
    }
}());
// then do it
var snd = Sound("data:audio/wav;base64," + base64string);

var snd = new Audio("data:audio/x-wav;base64, <URI data>");
snd.play();

There is no need to declare splash as an object variable.

Base64 conversion can be done easily from: https://dopiaza.org/tools/datauri/index.php