AutoAmplifier

AutoAmplifier is a simple app that sets your media volume according to the noise in your surroundings. For example if you decide to go out of a library and get on a bus, AutoAmplifier automatically adjusts the music volume so that you don't need to reach out for your phone and set the volume manually.

The configuration is really simple - just set the minimal volume that you want in quiet environment, corresponding level of noise and then do the same thing with noisy environment settings.

If you want to change your volume but you don't want to mess up your settings, simply open your status bar where you can increase or decrease the volume and stop amplifying.

This app is completely free without any ads.

Permission explanation:
Camera/Microphone - this app uses microphone to adjust volume, but it doesn't use camera

Source code:
This app was published under GPLv3 and is available on https://github.com/brightify/autoamplifier