Acoustics Explained
Noise in our workplaces, restaurants, schools, and healthcare environments are the single most troublesome issues expressed by all those who use them. Before we can help create an acoustic solution, let’s take a step back to understand what’s happening in these situations.
Sound is energy. When soundwave energy encounters a hard surface, one of four things happen:
- The energy transitions thru the surface.
- The energy is absorbed by the surface.
- The energy is reflected away – called a bounce or reflection.
- The energy is angled away in a different direction, this is called diffusion.
A great way to visualize how energy reacts to surfaces it encounters is to think of bouncing a basketball. You bounce that basketball on a hard surface and the ball predictably returns with virtually the same amount of energy. Bounce that basketball on a pillow, and the ball hardly bounces up, if at all. The energy the basketball carried was absorbed by the pillow. Likewise, when sound energy meets a solid surface, the bounce is much greater than when it encounters a soft surface.
Soft surfaces will not reflect as much sound energy as hard surfaces, but rather absorb it and stop the bounce. Hard surfaces reflect soundwave energy away. In spaces that you do not want any echo or reverberation, soft surfaces would be the most appropriate.
Echo
Whenever we hear a sound, we most often hear it from the source – “Direct Sound”. In cases where echo is present, we also hear that same sound, but it has been reflected or bounced off surfaces around us; floors, walls, ceilings, streets, rock canyon walls. These reflected sounds are called “early” and “late” reflections. These “reflections” arrive to our ears after the direct sound causes what we experience as echo.
The way to reduce echo is to introduce surfaces that are effective at absorbing soundwave energy. As in the pillow example, when soundwaves strike these soft surfaces, their energy is absorbed, leaving less energy to bounce or be reflected away.
We measure a materials ability to absorb sound energy with an NRC rating (Noise Reduction Coefficient). The NRC rating scale runs from 0 to 1.0. The higher the rating, the more effective the material is at absorbing sound. A 0.9 panel is better at absorbing sound than a 0.5 panel.
