How does convolution reverb work

Conceptually, how does real time convolution reverb work? Ask Question. Asked 8 years, 1 month ago. Active 6 years, 8 months ago. Viewed 7k times. But this raises 2 issues: Would the computer be able to perform so many convolutions every second? If anyone could help explain, that would be great. Improve this question. Add a comment. Active Oldest Votes. Improve this answer. This has a bunch of advantages: Less memory Less MIPS It's parametric, so different parameters like "room size", "reverb time" , "color", etc.

If done well, it actually sounds better. Hilmar Hilmar The question was specifically about convolution reverb, and this answer is specifically about algorithmic reverbs And it is reckless to say that algorithmic sounds better because it just sounds different.

Take Altiverb, for example A good pair of headphones, close your eyes, and you're inside Sydney's opera house. And you CAN tweak parameters like length, color, etc.

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Convolution is one of the more sophisticated processes regularly used in audio production. Its ability to accurately impart the characteristic timbres of spaces and objects on other signals is useful in both sound design and standard processing applications.

There are a wide range of convolution plug-ins available, each offering their own additional parameters and impulse responses. Convolution is a type of cross-synthesis, a process through which the sonic characteristics of one signal are used to alter the character of another. To an extent, this would be another form of cross-synthesis. However, there are no oscillating waveforms involved in the convolution process.

Instead, we work with two audio sources, an input signal and an impulse response. The input signal is the sound that will be affected, while the impulse response contains the sonic characteristics of the space or object that we will impart on the input signal. An impulse response is created by playing a sound, or an impulse, in a space. Microphones are used to record the resulting audio.

Ideally, the initial impulse would be edited out from the recording, leaving just the acoustic response of the space. This would leave a pure signal of the space, rather than including another sound with the space. Regardless, most convolution plug-ins can use information from any audio file as the impulse response to affect the input signal. The convolution process is used in some of the most powerful yet CPU-intensive reverb units on the market, convolution reverbs.

Ever want to hear yourself playing the piano on stage at Radio City Music Hall? With convolution reverb, you can! Developers travel to famous spaces around the world to record and collect impulse responses, and even do the same in everyday spaces like bedrooms and car trunks.

The leading plug-in developers take great care to record the impulse responses, so these plug-ins are able to almost perfectly recreate the reverb qualities found in different spaces. Convolution reverb plug-ins will also tend to include all adjustable standard reverb parameters decay time, adjustable level for early and late reflections, reverb frequency response, etc.

Reverb settings can be customized even after loading an impulse response, allowing for extreme fine-tuning. As mentioned before, convolution can be used for creative sound design. Instead of using those that capture the acoustics of a large room, we can use impulse responses that capture the sonic characteristics of a metal bowl, a cardboard box, a car trunk, etc.

We can even use contact microphones to record vibrations within each of these items. The vibration recordings can be used as impulse responses to give a new character to any other sound. Naturally, this application of convolution generally has more of a textural and timbral effect on the input signal than an ambient effect. Because of this, we can use these interesting spaces and objects to give life to bland instruments and percussion.

This can be done subtly to add a light layer of texture to a sound or it can be overdone to create an entirely new sound. Essentially, convolution is the process of multiplying the frequency spectra of our two audio sources—the input signal and the impulse response. By doing this, frequencies that are shared between the two sources will be accentuated, while frequencies that are not shared will be attenuated. This is what causes the input signal to take on the sonic qualities of the impulse response, as characteristic frequencies from the impulse response common in the input signal are boosted.

This will allow us to hear the effects of convolution clearly in all frequencies. Next, we need to choose an impulse response. Thankfully, Trash 2 has a whole host of impulse responses for us to choose from, as well as the capability to load in your own impulse responses if you wish to do so.

Listen to how the timbre of the acoustic guitar becomes more and more affected—more and more like the glassy, small ambience of a fishbowl:. This is obviously a more experimental use of convolution, more applicable to sound design than anything else, but convolution reverb follows the exact same principle. Instead of a fishbowl, the impulse response would reference the sonic qualities of something like the Sydney Opera House. The process needs thickening and blurring to suppress resonances from building up, so modulation is used to solve this problem.

Modulation in reverberant environments is not something we are traditionally used to hearing because real rooms would have no perceptible time-based variability in them unless the room is physically changing. Any movement of air or people within a room is typically imperceptible. The modulation of classic reverb devices has, however, become something we expect to hear in reverbs used for music as it is psychoacoustically very satisfying.

It helps synthetic reverb blend with its source and gives a reverb tail a lush organic quality. Registration number Cookies Policy Privacy Policy. Hit enter to search or ESC to close. What Is Convolution Reverb? A Reverb primer There are five basic types of reverb used in music production. Natural reverberation; recordings made in real-world spaces like chambers and concert halls, often these spaces are designed to be acoustically pleasing Plate reverb; a suspended rolled steel plate set resonating with a set of transducers speakers to excite the plate, pick-ups to capture the reverb Spring reverb; from Hammond organs and guitar amplifiers to large bespoke designs; requires transducers similar to a plate reverb Algorithmic synthesis; attenuated delay loops with injections and reads at various points, beginning in the s with devices like the Lexicon and EMT Convolution reverb ; a sampled capture of reverb is applied to an audio stream digitally You can read a little more about the history of reverb in another article.