What is reverb?

Reverb stands for reverberation. It is the natural echo or reflection of sound that occurs in a space. 

As the soundwaves travel through the air, they get reflected by the walls and bounce around between them until they have lost all their energy. 

While the first or early reflections usually consist of only a few sounds, the spacing between them quickly gets to a point where we hear them as one continuous sound.

You can quickly check the reverberation of a room by snipping your fingers and listening.

Reverb consists of several parts:

• Sound source or impulse sends sound waves into the room
• Initial or Pre-delay is the first part of the reverb. It depends on the distance between sound source and the closest reflective surface
• Early reflections come next
• Followed by late dense reflections

As you can see, the high frequency content decreases over time. A reverb can be tailored by adding absorptive materials that dampen and shorten it. Diffusors often create a more homogenous reflection pattern and make the room drier. See the graphic below

Churches have extremely long reverb time to support choir singing. Recording studios usually have a much shorter and more controlled tail. Especially voiceover booths are usually very dry.

You have most likely experienced this before when moving into an empty flat or house. It is hard to understand other people talking because there is so much reverb. But once you put in a couch and some shelves, it quickly gets much more controlled.

Here is an example of a completely dry voice recording vs. the same recording with a subtle reverb added. As you can hear, the dry version almost feels unnatural, while the one with reverb feels a lot nicer.

Different methods of creating reverb for audio productions have been developed over the years.

First, actual rooms or so-called reverb chambers were used, but ways to emulate reverb were developed and evolved in the past few decades.

Let's take a look at the different types of reverb, their history, and primary use cases.

A reverb chamber is a small room with reflective surfaces designed and angled to create a desired sound while avoiding parallel surfaces, resonance buildup, and flutter.

In 1947, Bill Putnam was the first engineer to use artificial reverb on a record. He placed a speaker and a microphone in the studio's bathroom as the first documented reverb chamber.

The song became a hit. Soon after, all major studios worldwide were building reverb chambers.

A speaker plays the signal into the room, while one or two microphones, which are strategically placed, pick up the reverberation of the room. This signal can be mixed with the original sound.

A plate reverb is a type of artificial reverb created by sending sound through a large, thin sheet of metal, simulating the reflections and decay of a natural reverberant space.

In 1957, the German company EMT made the next giant leap with their plate reverb EMT140.

This behemoth is 2,4 meters long, 1.2 meters high, and weighs around 270 kg. It features a spring-mounted metal plate held in place by a metal frame, all of it placed in a heavy wooden enclosure.

The plate is excited by a transducer, and a pickup records the reverberated signal. With two pickups, the reverb can even be Stereo.

Physical dampeners are used to lower the reverberation time.

While it may not be the most natural sounding method, it was used on so many records that people grew to like the sound of it.

Reverb plugins, like RO-GOLD by Black Rooster Audio, emulate this process.

A spring reverb uses metal springs (instead of a plate) and is typically used in guitar amps.

A similar concept came to life in the form of the spring reverb, but a spring reverb takes much less room and space. That's why they found their way into amps and mixers.

Spring reverbs were initially invented for the famous Hammond organs but quickly got adopted for guitar amps, which is their most common use to this day.

Algorithmic reverb uses a series of calculations (algorithm) to simulate the acoustic behavior of a physical space or devices like a plate reverb.

While they are complex to develop, they can be tweaked in many ways, giving the user great control over the parameters.

The most famous algorithmic reverbs are the Lexikon 480 and the Bricasti M7.

Convolution reverb uses impulse responses of existing spaces.

Convolution reverb uses an IR (Impulse Response) of an existing space to recreate the sound characteristics of that specific room.
A sine sweep or an impulsive sound containing all frequencies is played and recorded with a microphone placed inside that space to capture it.

This impulse response can then be imported into a convolution reverb plugin and be used to place different sound sources inside a virtual copy of the room. 

Once a room has been measured, it can be perfectly simulated with a convolution reverb. This method also recreates specific audio gear like guitar amps or speaker cabinets.

While convolution reverbs usually sound more realistic than algorithmic reverbs, they are much more CPU-intensive.

The most known convolution reverb is probably the Altiverb by Audioease.

While technologies have evolved very far when it comes to creating realistic-sounding spaces, it is still common practice to try and capture the room you record in with some room microphones if the room sounds good. Sometimes, the real thing is just perfect.

Given the rise of home and semi-pro recordings, it is less and less common to have the luxury of having a dedicated drum room. Because of that, the modern approach is to get a dry recording and then add the space in post-production.

It is easy to add space, but removing unwanted space from a recording can become very difficult.

If you like to experiment, you can simply try the rooms you have available to you. Putting a speaker and a microphone in a staircase can work much better than you might expect.

Some unique spaces will sound like nothing else. A nuclear power plant, for example.

In the video below, you can hear how an electric guitar sounds in a nuclear power plant!