In case you don't read reviews of free apps before downloading them, this might be of interest to you. Sounds like a cool app if you're a stupid kid who enjoys annoying your whole class (like me.) However, after reading the reviews, I quickly deleted this app. About one in every ten reviews claim that the high-frequency sound actually BLEW OUT the speakers on their device. Only a few mention which device they had (I've only seen iPhone 3G.) So use this app at your own risk.