What is meant by ‘good acoustics’? What makes some spaces carry sound so well, that a person doesn’t need to speak or sing very loudly to be heard way back?
In: 45
Human perception of sound is a big factor in the acoustic performance of a space. You have to understand the way our brains integrate incoming sound information into a complex 3-dimensional sonic picture.
The most important thing to realize is that the straight line from the sound source (emitter) to the listener is the direct sound. The sound emitter actually radiates sound in all directions in deep bass and as you go higher up toward treble shifts toward a tight beam. This off axis sound bounces off every surface, but each time it reflects it loses some energy to absorption by the surface and the air itself.
The key here is that bounced sound that arrives very close in time to the direct sound is perceived by our hearing as being a part of the original sound. These are called early reflections by acoustic engineers and tend to reinforce the sound.
Late reflections that arrive just long enough after the original direct sound to be perceived as different from it are destructive. That is, they reduce our ability to make sense of the original sound.
Very late reflections fall into the category of reverberation. They arrive late enough that they don’t interfere with the direct sound and can be pleasant, giving the listener a sense of the spaciousness of the environment.
The secret to acoustic engineering is to both absorb and diffuse the destructive reflections that can make the sound confusing to the ear. Absorption reduces the energy of early reflections while diffusion scatters them, pushing them more into the category of reverberation.
There is a lot more to acoustic engineering than just this. Parallel walls tend to cause troublesome flutter echoes as sounds ping-pong back and forth between them. Absorption can reduce echoes and making the walls non-parallel or curved can eliminate them.
Latest Answers