The next time you need to make your iPhone sound louder or any smartphone for that matter, just get a cup. iPhone works the best because it has speaker on the bottom. The sound from the phone apparently gets twice as loud just with this simple trick.
The glass is no replacement for speakers and will not help you bring down the roof. What it could do was help you in situation where you needed to get the volume a little louder than what it is.
The video by Mobile Crunch explains how:
