iZotope RX
A restoration suite that scrubs recordings clean of noise, clicks, hum and coughs — post-production's default fixer.
iZotope was founded in 2001 in Cambridge, Massachusetts, and shipped the first RX in 2007. The core idea is spectral editing: audio is shown as a spectrogram in which a phone buzz or a creaking chair appears as a distinct smudge that can be selected and removed, much like retouching a photo. Around that the suite has grown modules for denoising, de-clipping, de-reverb and dialogue isolation.
From roughly version 7 onward the most impressive modules rely on machine learning, and the line between restoration and source separation has largely dissolved. The program is now as standard in a film mix as a compressor, and it has rescued countless unusable recordings — or, depending on your perspective, taught location sound crews that it'll get fixed in post.