Grandma Moon Speaks: Reverberation and Echo

Topics Covered:

  • Reverberation
  • Echo

You can’t stay the same. If you’re a musician and a singer, you have to change, that’s the way it works – Van Morrison

Sound travels in all directions. It can reach you directly, and it can also reach you after bouncing off surfaces. There will be a time difference between directly heard sounds and reflected sounds, and we hear the sound ‘twice’ or more (depending on how many times it is reflected and still has enough energy to reach your ears).

This phenomenon happens all the time because sound always bounces off surfaces. Usually, the walls of a room are close by, and the speed of sound is fast enough for the lag to be indistinguishable. Other times the surface that receives the sound wave absorbs it, and almost no perceivable sound is reflected.

When the walls are close by, and the reflected sounds arrive at the ear almost instantaneously with the original sound, what we perceive is a ‘prolonged effect’ – which is one reason why you might sing better in the shower than outside it. The shiny tiles reflect your singing from all sides, enveloping you in your own majestic performance.

This effect of the original sound being prolonged due to reflections is called reverberation.

When the reflected sound is heard distinctly from the original sound, the effect is called an echo.

The key difference between an echo and reverberation is that in an echo, two distinct ‘copies’ of the original sound can be distinguished. In a reverberation, or reverb, it appears as one prolonged sound.

The boundary between a reverb and an echo is typically at the 0.1 second mark (100 ms), because that’s approximately the time a sound ‘stays with you’ once you’ve heard it.

Different rooms have different reverb ‘signatures’. Through our experiences we are trained to ignore reverberations in real life, but observing this quality helps mixers recreate a room tone or ambience in post production.

Takeaways:

  • The effect of a sound being prolonged due to reflections of it hitting the ear is called reverberation.
  • When reflected sounds are heard distinctly from the original sound, the effect is called an echo.

Links for further study:

Next: Coming Soon
Previous: Loudness or Volume