Bluetooth headsets use two audio profiles: A2DP (high-quality music/playback) and Hands-Free/HFP (for calls with mic). When testing, make sure your headset is connected and in call mode. On Windows: Settings > Sound > Input > select the headset's Hands-Free variant (not the Stereo variant). On Mac: System Settings > Sound > Input > select the Bluetooth headset. Open an online mic test and speak — if you don't hear yourself in playback, the headset's mic may be muted (check the physical button) or the wrong profile is active. Bluetooth mic quality is noticeably lower than USB due to bandwidth limitations of the HFP codec. If the mic sounds muffled or drops out, keep the headset within 3 feet of your computer, remove obstructions, and check the battery level.