Sidetone is the audio feedback of your voice that you will hear when speaking into the microphone. Sidetone helps you know how you are being heard by others on the call. On H3000 sidetone will be enabled once the microphone is enabled. You can manually enable/disable the sidetone by pressing the central button on the earcup three times, but the sidetone setting will return to default when the headset is powered off and powered on again. Currently H3000 sidetone level cannot be adjusted.