With the absolute volume function of Bluetooth on Android, the volume of the phone and the Bluetooth device change at the same time. This option is enabled on Android devices by default. You can adjust the volume of your smartphone individually by turning off the Bluetooth volume.
Absolute Bluetooth volume is a feature that synchronizes the system volume on your Android phone with the volume of a connected Bluetooth audio device, such as headphones or speakers. This allows you to control the volume in one place. But there are devices that are incompatible with absolute volume control.
To turn off the absolute volume of Bluetooth, you must first turn on the Android developer settings. On your Android device, launch the Settings app and tap About phone. Depending on your version of Android, scroll down to “Build Number” or “Model Number” (depending on what you see on the page).
Tap the number seven times in a row until you are notified that you have enabled developer mode.
Swipe down from the top of the screen to see the control panel, and tap Bluetooth to turn it off.
In Settings, click System and tap Developer Options. Find Mute, and then swipe right.
After you turn on Bluetooth again and connect the Bluetooth audio device, you will see that the volume controls of the phone and the Bluetooth audio device now work independently.