Welcome to the Poly community.
The sidetone of our Blackwire series can be get adjusted via the Windows Sound Control panel. Please follow the following path to get to the setting: Windows Sound Control Panel>Playback>Double click the Blackwire>Levels>Sidetone.
Also on high sidetone levels, the headset's microphone may start picking up the environmental airflow and feeds it back to the speaker which results in an audible hissing sound.
Please note that the sidetone setting is not available if the Blackwire series are used with a Mac.
Please ensure you always check the FAQ's.
Please remember, if you see a post that helped you, and it answers your question, please mark it as an "Accept as Solution".
This forum reply or post is based upon my personal experience and does not reflect the opinion or view of my employer. Poly employee participation within this community is not mandatory and any post or FAQ article provided by myself is done either during my working hours or outside working hours, in my private time, and may be answered on weekends, bank holidays or personal holidays.