If you want to create ambience in your recordings, the use of reverb is an essential tool.
The Science of Reverberation
In 1890, Wallace Sabine studied how absorption impacted reverberation time. He came up through his studies the relationships among elements described in a mathematical equation (the Sabine equation) showing how long it took for sound to decay from a 60dB level. In his studies, he found that the time to decay 60dB depended upon a number of key factors:
- The size of the room
- The surface area in the room
- The total absorption in the room
Intuitively, these elements make sense.
Let’s consider a 10′ x 10′ x 10′ cube room versus a 5′ radius spherical room. The total volume of the square room is 1000 feet. The spherical room is 523.6 feet (4/3 x PI x radius cubed). The sphere is much smaller because it excludes the empty volume within its cube. We know that when we are inside a smaller room when we speak, sound travels a much shorter distance and bounces faster. If you put a lot of furniture in the room (say sponge furniture) the surface area of the room gets smaller.
Putting this all together, we get a good sense of how sound reverberates within space.
A very common audio effect found in most Digital Audio Workstations (DAW) software today is the reverb effect. It simulates the characteristics of sound within space, its reflection within that space, and the duration in time. The sound initially builds up to maximum amplitude bouncing repeatedly within the space, and then decays to zero.
In the older days, to create this effect on a physical level, people would use halls and echo chambers. Sound would be sent from the mixer over to the studio monitors (“Dry” signal) that existed in the chamber. Carefully positioned microphones within the chamber would pick up the new effect (“Wet” signal) as it bounced among the walls and sent back to the mixing console.
If you were someone who didn’t have a chamber (who did) you were out of luck. Fortunately, in the 1950’s, a gentleman by the name of Wilhelm Franz founded Elektro Mess Technik (EMT). The company was the leading manufacturer of the world’s finest record turntables. While creating fantastic turntables, Mr. Franz came up with the idea of simulating reverberation using analog measurement on steel plates. EMT produced a series of reverberation machines dubbed the EMT 140, 240, and 250. The EMT 140 was the original and the model reverb standard used in simulations today.
It consists of a thin steel echo plate that was hung with wire clips inside metal walls (think of it like a metal gong that is suspended). Not easily movable (weighs 800 pounds!) it is the size of a ping pong table and stands upright vertical. Sound would be routed into and out of the EMT 140 with the desired reverb effect.
Reverb Software Plugins
Today, you don’t have to own one of those EMT 140 beasts to get reverb into your audio recordings. Instead, you can buy software plugins that simulate from sampled sounds. When generating synthetic reverbs, there are two methods:
- Convolution – Generated by actual space samples
- Algorithm – Generated through algorithms based on modeling data
Generally, you’ll want to stick with the convolution method as it will reproduce a better sound that isn’t so fake as the algorithm method.
Some high-end reverb plugins to consider are:
- EMT: Universal Audio EMT 140 Classic Plate Reverberator ($199)
- EMT: iZotope Nectar 2 ($299)
- Lexicon: Lexicon MPX ($100)
- Lexicon: PCM Native Reverb ($719)
- AudioEase AltiVerb ($595)
If you are looking for a EMT 140 reverb plugin, the Universal Audio plugin is the only one endorsed by EMT Studiotechnik. Sounds are sampled from a true EMT 140 in one of the most famous rock recording studios located near me at The Plant in Sausalito, California. The Lexicon PCM Reverb Bundle is a very complete plugin that offers plate, room, chamber and hall reverb models. So you get the best of all those worlds (although the price is quite steep).
Altiverb is a very interesting solution taking its modeling data from recording concert halls, rock studios, and stadiums from around the world.
If you’re not into software plugins, reverb processors are available in hardware from many manufacturers.
- TC Helicon
- Bricasti Design
These are rack mounts and audio hardware devices for use in larger music production environments.
The TC-Helicon VoiceTone Harmony for example, is a rich featured vocal effects processor that includes reverb.
Reverb isn’t just an effect. There is a whole history behind creating it with a rich past. When you use reverb, think of it as adding sound character that attempts to emulate a particular environment space. Unlike Echo and Delay, reverb can add a little more random repetition in your recordings.
There are many different ways reverb is generated including steel plate simulation, digitally, and through sampled spaces.