This app generates tones between 14,000 and 20,000 Hz, which are on the higher end of the ear's limitations. Generally only young people can hear these tones.
This app simply endlessly plays a tone selected by the user which they cannot hear, but younger people can, which is extremely annoying.
This app only serves one banner ad, which is why the app needs internet permissions.
High frequency sounds are annoying, but high frequency sounds over 100 decibels are dangerous. Don't play sound loudly near your ears. Use this app wisely.
To get the most out of the app, turn your media volume up, or perhaps connect your device to a set of speakers.