No learn function; you must manually set threshold. GUI is basic but functional. 3.2 ReaFIR (Cockos) – Most Powerful | Aspect | Details | |--------|---------| | Developer | Cockos (part of REAPER) | | Type | FFT-based subtractive / dynamic EQ | | Formats | VST, AU (free standalone) | | OS | Windows, macOS, Linux | | Key feature | “Subtract” mode with noise profile capture |

Instead of broadband subtraction, it compresses/expands specific frequency ranges when they fall below a threshold. Effectively ducks hiss in silent passages.

No free plugin matches iZotope RX’s machine learning or spectral repair, but for removing hiss, hum, and ambient noise, the above four plugins are professional-grade and cost nothing.

Records a noise print from a selection of audio (silence section), then subtracts that exact spectral shape. Works like iZotope RX’s Voice De-noise but free.

Extremely effective for steady-state noise (air conditioners, preamp hiss). Can cause “underwater” artifacts if reduction set too high (>30 dB).

Uses an adaptive noise floor estimation with adjustable thresholds. Unlike simple gates, it reduces noise across all frequencies proportionally.

Trained on thousands of voice and noise samples. Uses deep learning to isolate speech even under heavy background (e.g., traffic, café noise).