A free app for Android, by West-Hino.

If you are looking for a simple and convenient way to keep your device secure, the Ringer Mode Lock app is what you need. It lets you disable the alarm sound on your Android device and also prevents anyone from changing the device’s volume, while you are using the app. 

Ringer Mode Lock is a very useful app that you can use to make your phone more secure and also to prevent anyone from changing the device’s volume. It is a simple and convenient way to keep your device secure and also prevents anyone from changing the device’s volume, while you are using the app.