No to je taky nesmysl:

<a href="#"><img id="imBut15" src="4.png" onclick="audio.pause(); audio.currentTime = 0; audio.play();" onMouseDown = "document.images['imBut15'].src = '4s.png'" onMouseUp = "document.images['imBut15'].src = '4.png'"></a>
<script>
var audio = new Audio('sklo.mp3');
</script>

<a href="#"><img id="imBut1" src="4.png" onclick="play()" onMouseDown = "document.images['imBut1'].src = '4s.png'" onMouseUp = "document.images['imBut1'].src = '4.png'"></a>
<script>
var audio = new Audio('sklo.mp3');

function play() {
    audio.pause();
    audio.currentTime = 0;
    audio.play();
}
</script>