Frequencies App for iOS

Plays frequencies only teens can hear.

View project on GitHub


Some call it a "dog whistle", while others call it "annoying". There are producible sounds that dogs can hear which humans can't, but did you know that there are sounds that only specific age groups can hear? That's right, you can now drive your little brother crazy with this app. You can even play these sounds in class and annoy everybody in the room except the teacher! Ultimate prank: connect your device to load speakers at a party and have all the kids freak out except the adults.

Frequencies plays fifteen different tones ranging from 8 kHz, which can be heard by mostly everyone, and 22 kHz, which can only be heard by children under 13 years old.

Frequencies also has a "pulse" feature, which plays tones in a way that is noticeable by playing them in a pattern, like repeated beeping noises, instead of playing the tones continuously.

Set a countdown-timer to play a frequency! The timer will keep ticking as you put your iPhone in your pocket, when all of a sudden, everyone is looking around wondering who is playing it! It's obviously not you... your phone is in your pocket...

Have pets? Frequencies can get their attention by producing a 22 kHz tone, which can be heard only by small children and most animals, like cats and dogs. What? You thought that these tones can only be heard by dogs? Almost all mammals have better hearing than us. We can only hear up to 23 kHz, while dogs can hear up to 45 kHz, cats up to 64 kHz, and rabbits up to 42kHz, and so on.

One more feature that Frequencies has that similar apps do not is the ability to play these sounds while the screen is locked or with the silence switch on. So you can start playing a sound on your device, turn the screen off, and walk into class with it in your pocket! Because of it's very high pitch, the source of the sound is very difficult to locate, yet still very annoying; nobody will know it's you, unless, of course, you're the only other person in the room.

Authors and Contributors

Frequencies, formally known as Frequencies Pro and "iHear?", was created in 2009 by Corey Stewart (@itscory). It had since made the France App Store's top 15 free apps. As of April 2015, it was downloaded over 478,000 times worldwide.

Frequencies was recently open-sourced and has no other contributors.

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