You can switch off the mute reminder tone either with the Jabra Direct software (to be installed on your PC) or directly on the headset (chapter 7.7 of the user guide):
- Press and hold Volume+Silent until the headset says 'Setup'.
- The very first setting is for the mute reminder, the headset says the setting.
- Press minus once, the headset should confirm that the reminder is 'off'.
- Confirm with the round 'multifunction button', the headset says 'confirmed'.
- Press and hold Loud + Quiet together until the headset says 'Goodbye' - done!

The manufacturer does not seem to provide any information on this.