You can raise or lower the volume by tapping the (+) Button or the (-) Button. The volume is set and maintained independently at different levels for each audio source even when you turn off and on the headset. For example, once you set the volume for mobile phone hands free, it will not change even if you adjust the volume for your Bluetooth MP3 music. So you can always maintain the preferred optimum volume level for each audio source.
WARNING Use of the product at a high volume for a long period of time may damage your eardrums or hearing ability. Keep the volume at a modest level to prevent damage.