Audacity

Audacity is the long-standing free, open-source audio editor — multitrack recording and editing with noise reduction, normalization, EQ, and a deep library of effects. For a streamer it’s the workhorse for anything off-stream: cleaning up podcast or VOD audio, recording and polishing voiceovers and intros, or trimming clips before they go out. It runs on Windows, macOS, and Linux, and it’s completely free with no paid tier.