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
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
- 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
- RealReverb plug-in
(direct-X or WinAmp) Freeware - very easy to use!
2.0 from SoundsLogical: many
filtering modules connected by a block-diagram user's interface - includes
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
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
Impulse Reverb by Christian Knufinke - free VST convolver (2 channels)
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)
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.