This is a summary of an article about how reverberation affects our perception of music, that was originally featured on our blog.
When we listen to music either live or through a sound system, those sound waves we hear are interacting with the environment all around us. Music will sound different when played in a recording studio compared to a purpose-built venue, or a living room.
So just what are the rooms around us doing to our music, and how does it affect our experience?
Reflections and reverberation
Sound bounces off of solid objects, and this includes room surfaces. When you pop a balloon in a church, and you hear a long decay of the sound after the event, this is the effect of sound bouncing around the room and back to your ears. This effect is called ‘reverberation’.
Direct sound vs reflected sound
The first sound that reaches your ears is the ‘direct sound’. This is sound that has travelled in a straight line between the source and the listener.
After the direct sound arrives, reflected sounds (which took a longer path to get to your ears), start arriving shortly (milliseconds) after. As the reflected sound waves travel further and bounce off of walls, ceilings and objects, they lose some energy, so they are generally quieter than the direct sound.
Depending on when these reflections arrive at your ears, and how loud they are, this can alter your perception of the music.
0–1 millisecond
Reflected sound arriving in the first millisecond after the direct sound reaches you, can alteryour perception of where the sound came from.
0–5 milliseconds
Reflected sound arriving in the first 5 milliseconds is generally perceived as being one entity with the direct sound. This effect is known as fusion.
5–50(ish) milliseconds
At approximately 50 milliseconds, the fusion effect begins to break down. This point in time is called the ‘fusion breakdown threshold’.
Envelopment
One of the key experiences that listeners appreciate in the best concert halls is ‘envelopment’.
Envelopment occurs when early reflections (those in the first 80 ms in the case of live classical music), arrive at the listener from directions other than the direction of the source.
Late reflections (after the breakdown of fusion)
Late reflections are perceived as reverberation — this is the sound you hear decaying in a church or concert hall after you clap your hands together or pop a balloon.
Clarity
If the Clarity is too low, the listener might have trouble distinguishing musical notes from one another.
What’s the difference between reverb and echo?
Reverb is typically perceived as the decay of an earlier sound, where each reflection has (on average) less energy than the last.
An echo is perceived as a distinct reflection (like a repetition) of the initial sound.
In a music studio or audio suite, we generally want to eliminate (or substantially reduce the level of) the very earliest reflections.
In a venue for amplified popular music, a reverberation time of between 0.5 and 1.0 seconds might be suitable.
In a venue for classical music, reverberation times as long as 3 or 4 seconds are not unusual.
Summary
Rooms and objects reflect sound.
Direct sound is the first sound to arrive at our ears, having travelled in a straight line from the sound source.
The early reflections to arrive at our ears fuse with the direct sound, and alter our experience of it.
The late reflections sound like a separate entity — a decay of the original direct sound.
The boundary between early and late reflections is variable and depends on what it is we arelistening to (speech, popular music, classical music).
Suitable suppliers of sound-absorbing materials include Ecophon, GIK Acoustics and Impact Acoustics.
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References
Acoustics and Psychoacoustics, David M. Howard and Jamie Angus, 2017
Concert Halls and Opera Houses: Music, Acoustics and Architecture (Second Edition), Leo Beranek, 2004
Rock and Pop Venues: Acoustic and Architectural Design (Second Edition), Niels Werner Adelman-Larsen, 2021
The Precedence Effect, Litovsky et al., 1999
