Convolution is a mathematical operation which consists on the filtering of one signal (the "source") passing it through an FIR (Finite Impulse Response) filter, which is simply another signal. The operation is quite simple in frequency domain, where it reduces to (complex) multiplication between the spectra of the signals.

For Auralization, a dry (anechoic) signal is processed through binaural impulse responses, obtained from measurement or computed with Ramsete.

A more advanced process can be used for multi-channel Impulse Responses, for example B-format IRs for Ambisonics rendering. In this case, a multichannel convolver is required.

The ultimate application is however Ambiophonics, which requires simultaneous cross-talk cancellation and convolution with several independent room impulse responses.

Many software tools are available nowadays for performing the convolution real-time on a PC, without the need of expensive hardware (which was developed several years ago from Lake Technologies):

• Aurora software suite of Cool-Edit plugins (shareware)
• Adobe Audition (already includes a Convolver module)
• Samplitude 2496 (already includes a Convolver module)
• SoundHack program for Macintosh (to be verified, it implements a strange sort of circular convolution)
• Acoustic Mirror plugin from SONY Media Software
• RealReverb plug-in (direct-X or WinAmp) Freeware - very easy to use!
• WaveWarp 2.0 from SoundsLogical: many filtering modules connected by a block-diagram user's interface - includes convolution.
• The FIReverb Suite from CATT, produces synthetic (but realistic) multichannel impulse responses, includes a multichannel convolver.
• The BruteFIR software for Linux, by Ander Torger: multichannel convolver with source code available under the GNU public license. Great, very fast and completely FREE !!!
• Ambiovolver software from Jose' Javier Lopez - real time convolution of two input channels with up to 20 impulse responses, driving up to 10 loudspeaker - incredibly fast and solid, and FREE!
• Pristine Space by Voxengo - the first professional multichannel VST convolution plugin
• Super Impulse Reverb by Christian Knufinke - free VST convolver (2 channels)
• Waves IR-1 parametric convolution plugin - not just a convolver, gives complete real-time control over the sound
• Tascam Gigapulse - VST convolution plugin

However, here are the references also to three hardware convolvers actually available on the market:

• Yamaha SREV1 Digital Sampling Reverb (studio equipment, also suitable for impulse response measurements)
• Sony DRE-S777 Sampling Digital Reverb (studio equipment, only works with its own impulse responses)
• Lake Huron Digital Audio Convolution Workstation - complete solution for measurement and sound processing, with user-defined impulse responses. Powerful, but the hardware is a bit obsolete and it is very expensive.