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Posted by on Dec 29, 2012 | 5 comments

Recording Impulse Responses

With growing computing power over the last decade, convolution plugins have become commonplace. Some of the most common ones include Audio Ease Altiverb, Logic’s Space Designer, Avid TL Space, Waves IR-1 and McDsp Revolver. They are usually packaged with large and useful libraries of impulse responses (more on what all this means below), but what makes them really powerful is the fact that it is quite easy to record and use your own impulse responses. This not only helps ‘personalise’ your mixes, but is extremely useful in post-production and in the design of new sounds.

Each of the above mentioned plugins need slightly different techniques for creating a custom library of impulse responses. This article is a description of the general concepts behind recording good impulse responses and should be easily adaptable to any convolution/de-convolution tool.

What is convolution?

Convolution is the process where a single sample of a sound is multiplied by every sample of another sound. It is different from the plain multiplication of two sounds where a single sample of the first sound is multiplied by the corresponding single sample of a second sound.

Curtis Roads (The Computer Music Tutorial) describes convolution as:

Convolution of two audio signals is equivalent to filtering the spectrum of one sound by the spectrum of another sound. Convolution of spectra means that each point in the discrete frequency spectrum of input a is convolved with every point in the spectrum b.

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Posted by on Nov 1, 2011 | 1 comment

Altiverb Impulse Responses Available for Wwise

Audiokinetik has announced a new partnership with Audio Ease. Altiverb IR packages on Wwise.

Audiokinetic Inc. and Audio Ease B.V. announce a partnership where Audiokinetic will distribute award winning Altiverb Impulse Response packages for the Wwise convolution reverb plug-in. The first package will be available before the end of this year and will contain 49 impulse responses mostly oriented for the reproduction of outdoor environments. Reproducing outdoor environments is probably one of the most difficult tasks for sound designers today and this package arrives at the right moment for professionals seeking quality and realism in their games.

“At the design phase of our convolution reverb, we set a very challenging goal that we could have the best technology from the post-production world running in games, said Simon Ashby, VP Products at Audiokinetic. Given that our convolution reverb operates with high performance and that we proudly partner with Audio Ease, which is certainly the most respected player in this field, I think we can say that we have achieved our goal”.

“Convolution reverb approaches the real world so much better than synthetic reverb that it had no trouble taking over Hollywood film sound. I hope this set of movie post-pro Altiverb IR’s will help convolution reverb do the same in game sound, added Arjen van der Schoot, Co-owner of Audio Ease. We had been waiting for the right opportunity to start applying our IR’s in real time in games. When Audiokinetic came along, we did not hesitate. I believe we have chosen to partner with a company as devoted to impressive sounding audio as we are.”

Audiokinetik | Audio Ease

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Posted by on Jun 16, 2011 | 0 comments

IR Reverb Comparisons

I published an article on IR reverb and deconvolution comparisons on my blog. Quite a few people found it useful and Miguel thought it would a good idea to share it with the rest of the community who aren’t on Twitter. If you aren’t on Twitter, join now! The sound community is nothing short of fabulous.

After my previous post on recording and mangling IRs, I decided to find a way to use the sweep I recorded for Altiverb in other convolution reverb plugins. I also thought it would be a good opportunity to compare the sound of these plugins and listen to how differently they deconvolve sweeps. The list of plugins include:

This is not a comparison of their features but of how each one of them sound.

Deconvolution Comparison:

Preparation:

The Altiverb sweep generator produces a sweep with a start and end beep (which it uses for identification). Since most other deconvolution tools don’t recognize these beeps, I created two versions of the sweep – one with the beeps and one without and normalized them to -0.3dBFS. The recorded sweep at the venue also included broadband noise and AC hum, which Altiverb’s processor did a good job of neglecting. The other plugins weren’t as good and included the noise along with the impulse. To make the comparison easier I used some amount of noise reduction on both versions of the recorded sweep.

1. AudioEase Altiverb:

AudioEase’s IR Pre-Processor needs to be used to deconvolve a sweep that is usable in Altiverb. The process is very simple – select a folder with the recorded sweep (make sure they are stereo-split SDII files), an output folder (your Altiverb preset folder), an input description file (in this case, “Sweeps, not to be equalized”) and hit “Process”. Re-scan your IR directory in Altiverb and it should show up.

Here’s what the sweep recorded at the venue for Altiverb sounded like (with beeps, noise reduction and normalization). Make sure you aren’t monitoring too loud:

Continue reading and listening here.

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