SIR Audio Tools is an audio plugin developer based in Bielefeld, Germany, founded and operated by Christian Knufinke. The company began with the original SIR (Super Impulse Reverb), a freeware convolution reverb that became a widely used underground favorite before evolving into the commercial SIR2 and the present-day SIR3, which incorporates HDIR impulse responses produced in collaboration with Pinguin Ingenieurbüro in Hamburg.

Beyond reverb, the catalog covers a range of mixing and production utilities, including StandardCLIP (a clipper popular in modern loudness-focused mixing), StandardEQ (an equalizer), StandardGATE (a noise gate), SpectrumAnalyzer, and qwertyGO!, a keyboard-triggered sample player aimed at live performance and podcasting workflows. The plugins are sold individually rather than as a bundled suite, with both free and paid versions available across the line.

The brand is closely associated with its founder's solo development approach and has built a reputation in mixing and mastering circles, with StandardCLIP in particular cited as a go-to tool for transparent peak limiting on contemporary records.

SIR Audio Tools has 2 products cataloged on Equipboard, including Reverb Plugins and Mastering Plugins. Their gear is featured by 5 artists, with the strongest followings in Electronic. Notable users include Luca Pretolesi, Hard Driver, and Tom Hades.