Join Alex U. Case for an in-depth discussion in this video Simulating space with reverb, part of Foundations of Audio: Reverb.
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As reverb is in essence the sound of a space, it isn't surprising that we use studio reverb to simulate a space within our recording. Simulating space is itself a rich source of four families of effects that we talk about here: specific real spaces, generalized realistic spaces, spatial adjustments, and the creation of unreal spaces. Sometimes in music, our production challenge is to simulate a very specific real space. We might want to have the sound, the history, the feeling, the memory, the distinction, the sense of a very specific space with all the smells and sights that accompany it.
We might want our recording to have the sound of acoustic icons like Carnegie Hall in New York, or huge houses of worship like Notre Dame in Paris, or small performance clubs like your favorite place down the street. We might pursue other less obvious places, your high school gymnasium, a London tube stop, the stairs at work. You have in mind a very specific real space, and you use reverb to make it happen. Any reverb processor can do the job, a chamber reverb, a spring, or plate can be hooked up and processed to help simulate the sound of a specific real space.
But you are going to find digital reverbs are best suited to the task. Algorithmic reverbs with all their adjustable parameters can be tweaked until they match the sound of your actual desired space. But of course, convolution is a great way to go here if you have the right impulse responses. Drop Carnegie Hall onto the background vocals of your mix by instantiating a convolution reverb and loading in your favorite Carnegie Hall impulse response, if you have one. I am sure you could download one if you don't.
Note to self, capture impulse responses on every location recording gig, find some quiet time when the band is taking a break and grab the impulse response. Use the Convolution reverb's Measurement feature or record the loudest short click you can using a handclap, popping a balloon, or even hitting a snare. It will let you create the sound of this room later when you might want the sound of this room but don't happen to be there. Beyond music production video postproduction presents another very common audio challenge where we need to evoke the sound of a specific real space.
If you record Robert De Niro speaking his lines in a taxi during film production and then have to do some dialog replacement in a booth in a studio later, you're going to have to make the close mike studio recording sound like the boomed mike taxi recording. So in video production it can be helpful to capture the impulse responses for all places where the film was shot, indoors, outdoors, on cars, trains, and planes. And when it's time to dialog replacement in the studio, we reach for convolution as a tool to help convert those close microphone studio recordings into something more consistent with the specific sound of the production recording.
A generalized realistic sounding space is the second motivation for simulating space with reverb. We aren't always tied to one specific space. Sometimes a similar-sounding space will do. You may not need Boston Symphony Hall, just a symphony hall. You may not require Notre Dame specifically, just a large cathedral. Here we get to relax a little bit, and we are permitted to be more creative because we're no longer obligated to match a specific space. Instead, we get to create a realistic sounding space, but one with all the sonic features and details we like best.
The third spatial motivation for reverb might be called Spatial Adjustments. Spatial Adjustments can be necessary because we so often record our sounds using close microphone techniques. The desire for isolation and the creative motivation to explore the sonic impact of close microphone placement often leaves us with little to no recorded ambience or reverberation. We might introduce a subtle amount of reverberation focusing particularly on the early reflection part of the reverb rather than the late reverberant tail to create the sound of microphones having been a bit further away.
This can diminish any unwanted razor-sharp immediacy in our closed mike tracks pushing them away from a studio sound towards a more realistic aesthetic. If the artist or producer complains that the record sounds too multi-tracked, and they wish it to sound more live and more organic, consider adding some early reflections to your close microphone tracks to take the studio, close mike, vocal booth sound out of your recording and instead make it sound a bit more realistic. We don't have to decorate the track with a long lush wash of reverberation to create the sound of air moving.
It adds a sense of liveness to the performance, and it can widen the stereo image between the loudspeakers. There is a fourth category, we've discussed specific real spaces, generalized real spaces, and spatial adjustments. The fourth motivation is maybe the most fun. We are allowed to create the sound of a completely unreal space. In these instances we are allowed to freely and creatively try pretty much any parameter setting we wish. We are not bound by the physics of room acoustics, we just choose what sounds best.
For example, we might create a reverb whose early reflections are dictated by the geometry of a large hall, while the Decay time is more indicative of a small room. And we could have extended high-frequency decay time that essentially suggests there is no air absorption. So that's a large small room with no air. That's an impossibility for live performance, certainly an uncomfortable place to go. But we can create it in our recordings anytime we like as long as it sounds right.
These techniques can be practiced with the free Get in the Mix sessions, currently available for Pro Tools and Logic Pro.
- What is reverb?
- Understanding how acoustic reverb works in rooms
- Working with the signal flow, effects loops, and available CPU resources
- Understanding core parameters, like reverb time and pre-delay
- Simulating space
- Creating nonlinear reverb
- Building pre-delay effects
- Using reverse reverb
- Using convolution correctly