As people grow older, they suffer from hearingloss and can no longer hear high frequency sounds. RingTeen is anapp that plays sine wave ultrasounds, with frequencies ranging from8 khz to 22 khz, and allows you to set them as ringtones ornotification sounds. This way, your parents or other adults won'thear when you receive a phone call or a message. Alternatively, youcan use the app to play pranks on other people or to simply testyour hearing. The higher the frequency you can hear, the betteryour hearing is.

Try playing the ultrasounds starting with the highest frequencyand going down until you hear the sound playing. That ultrasoundshould be set as ringtone or notification sound. Typically,30-year-old adults won't be able to hear ultrasounds starting from17 khz and higher, though this varies from person to person.

Using the app is very easy:
- swipe up or down to scroll
- tap on a sound in the list to play it (or long-tap to loop it)and tap again to stop playback
- tap on the left icon to set the ultrasound as ringtone and tapagain to revert to your previously selected ringtone (you don'tneed to go to your phone's settings to do this)
- similarly, tap on the right icon to set the ultrasound asnotification sound and tap again to revert

Please note that your experience may vary depending on yourphone's volume level and speaker quality.