Under IE an embed tag is generated for the sound. It seems it has default height, so when it is appended to the form with JavaScript it may cause scrollbars if it has siblings with height set to 100%.
There are three possible workarounds
- set the form overflow to hidden with CSS, e.g. html, body, form { height: 100%; overflow: hidden; }
- remove the ShowSound property if it is less important than scrollbars and page layout
- use the following JavaScript function to remove the height from the embed tag:
		function pageLoad()  //Sys.Application.Load handler
		{
			if ($telerik.isIE)
			{
				var embed = $get("<%=rn.ClientID %>" + "_playAudio");
				if (embed && embed.tagName.toLowerCase() == "embed")
					embed.style.display = "none";
			}
		}
where rn is the server ID of the notification control. If more than one RadNotification is present on the page the procedure would have to be repeated for each one.