A free app for Android, by Inverse.AI.

MP4, MP3 Video Audio Cutter is an advanced, powerful, fast, and best MP4 video audio cutter, converter, and trimmer app. It’s compatible with almost all video formats. It can convert all video formats to audio formats, such as MP3, AAC(M4A,M4B), AC3, WAV, OGG, FLAC, MP4, MKV, AVI, 3GP, FLV, MOV, WEBM, M2TS, TS, MTS, MPEG, as well as convert from one format to another. With this, you can even adjust the volume and bitrate of the audio.

This app is very simple and easy to use. You can download it on Android devices.