estet-osa, вот, должно работать:
<div id="soundflash" style="position:absolute; z-index:-10; display:none"><object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=5,0,0,0" width="1" height="1"><param name=movie value="ссылка к swf"><param name=quality value=high><embed src="ссылка к swf" quality=high pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" width="1" height="1"></embed></object></div>
<label><input type="checkbox" onclick="sound()">Саунд</label>
<script>
function sound()
{
document.getElementById('soundflash').style.display='block';
setTimeout(function()
{
document.getElementById('soundflash').style.display='none';
},1000)
}
</script>