HTML : 
Replace - 
<label  id="addStoryimg" class="required">Add Story Images Here: <i>(size upto 4MB)</i> </label>

<label class="required hidden" id='addStoryAudio'>Add Story Audio Here: (only .mp3)<i> (size upto 2MB)</i>

JS -
Replace - 
In function showFileName( event ) , replace this line
var flag=checkAudioExtension(input.files[0]);

function checkAudioExtension(ext)
{
	var validImageTypes = ["audio/mpeg", "audio/mp3"];
	if ($.inArray(ext['type'], validImageTypes) < 0) 
	{
		$("#audioUpload-filename").text('');
		return false
	}
	else
	{
		fileSize = (ext['size'] / 1024 / 1024).toFixed(2);
		if (fileSize <= 6)		//audio file size upto 6mb
			return true;
		else
			showSnackBar('File is too large(max 6MB)');
	}
}

Replace function call also AudioSync.showfiles();

AudioSync.showfiles=function()
{
	var fileSize;
	var output = document.getElementById("uploadedImages");
	files = AudioSync.imageFiles;
	for(var i=0;i<files.length;i++){
		file = files[i];
		if(!file.type.match('image.*'))
		{
			continue;
		}
		else
		{
			fileSize = (file.size / 1024 / 1024).toFixed(2);
			if (fileSize <= 1)		//image file size upto 1mb
			{
				var picReader = new FileReader();
				picReader.addEventListener("load",function(event)
				{
					var picFile = event.target;
					var div = document.createElement("div");
					div.setAttribute("class","noPadding imgDiv");
					div.innerHTML = "<img class='thumbnail noPadding img-responsive' style='background-color: rgba(158, 158, 158,0.32);' src='" + picFile.result + "'/>";
					output.insertBefore(div,null);
				});
				 //Read the image
				picReader.readAsDataURL(file);
			}
			else
				showSnackBar('File is too large(max 1MB)');
		}
	}
}