What Is An Echo Chamber In Audio?

In audio production there are a number of effects that we rely on when processing sounds.

Reverb for example is an effect that is used to create space around sounds and give them more of a “wet” feel.

Echo is another effect that works similar to reverb but its essence is to create a duplicate of the original sound while add some slight reverberation.

Both reverb and echo effects can be created naturally but the norm for most people these days is to simply use plugins. They’ve certainly made things easier.

In this post I’ll discuss echo Chambers and briefly introduce you to a world of real echo and reverb creation.

With that said, What is an echo chamber in audio?

An echo chamber is any space that is optimized and purposely built to produce reverberated sound. They’re quite rare today and they’ve mostly been replaced with digital reverberation plugins. Echo Chambers usually used to be built for recording back when digital and hardware effects weren’t as common.

An example of the application of echo chambers is…when producers of TV programs or radio shows try to create an aural illusion to make a conversation sound likes it’s going on in a large room or a cave.

This can be easily achieved by playing a recording of the conversation in an echo chamber while using a microphone to capture the reverberation effects.

These days you don’t really have to go through the trouble of doing this. All you need is an effects unit or digital plugins.

Creation of Echo Chambers

Back in the old days of audio recording, commercial studios would have a room that they would call an ‘echo chamber’.

Unless a studio had been purpose-built, (which was rare back then and is even more rare now) then it would probably be a room that they couldn’t think of any other use for.

Preferably it would have hard surfaces and be one of irregular shape to let sound reflections bounce around unevenly.

If the space wasn’t hard or irregular enough as required, then you could easily use some large concrete pipes to bounce sound around a bit more. The pipes would have to be of large diameter.

There would need to be a loudspeaker In that room  and one or two microphones…but preferably two.

The reason of having two microphones is to create a stereo effect.

You’d also need one loudspeaker pointed away from the microphones.

If a recording engineer wanted reverb on an instrument like a guitar or vocal they could eaily send the signal to the loudspeaker.

Sound would then bounce around the room creating reverberation to be picked up by the microphone.

The engineer could then easily add the reverb to the mix.

(Side note: As you can obviously tell this isn’t as quick, easy or convenient as dragging and dropping a plug-in on mixer channel, but it works and perhaps most importantly, it is REAL and it creates a real sound texture that is difficult for a plug-in to accurately mimic)

The sound texture of reverb created in an echo chamber is authentic and unique and no other studio has the same room and therefore no other studio can reproduce the same exact reverb.

The Necessity of Echo Chambers

The development of artificial echo chambers was key for sound recording because of the many limitations of early recording systems.

..in the early days, commercial popular recordings were made in specially constructed studios.

These spaces were heavily insulated and acoustically treated to keep internal and external noises tamed.

They were also designed to not produce any internal echoes or sound reverberation.

Its safe to say that every sound in everyday life is a complex mixture of direct sound from the source and its echoes and reverberations, audiences naturally

found the ‘dry’ and reverberation-free sound of early recordings unappealing.

Consequently, record producers and engineers quickly came up with an effective method of adding ‘artificial’

echo and reverberation that experts could control with a remarkable degree of accuracy.

Creating echo and reverberation through the use of an echo chamber is not a big ordeal in theory. The physics is quite simple.

An audio signal from the mixing desk such as a voice or instrument is simply fed to a large hifi loudspeaker that is located at one end of the chamber.

Two microphones are then placed along the length of the room and these pick up both the sound from the speaker and its reflections off the walls of the chamber which is very important because we need both the audio signal and the effects of the echo chamber.

As a general rule of thumb, the farther away from the loudspeaker, the more reverberation the microphones csn pick up and the louder the reverberation becomes in relation to the source.

The signal from the microphone line is then fed back to the mixing desk, where the echo/reverberation-enhanced sound or wet sound can be blended with the original ‘dry’ input.