Please try the following to resolve your issue:
- Try clearing your Bluetooth mobile device from the BOSEbuild Headphones by disabling Bluetooth on your device. Pair the device and Headphones again.
- Check the volume level of the connected audio device. If the connected device has a variable audio output, adjust the volume level to 80 percent of its maximum.
- Try a different audio source to make sure it isn't an issue with the source.
- Try resetting the Headphones. For more information, see How Do I Restore The Headphones To Factory Default Settings