Room Echo – How Do I Fix It?

Room EchoRoom echo is what most people think of when referring to acoustic reverberation, and is a noise problem we've all encountered at one time or another.

What Is Room Echo?

Think about when you move into a new house and what it sounds like before you add things like drapes, carpeting, and furniture. Instead of a living room, it sounds like a public gymnasium. This is what most people describe as "room echo".

So What's Going On?

You have to remember that "sound is everywhere". That is to say, sound propagates in all directions simultaneously. Think of when you drop a stone into a body of water and you see the ripples of water move outward in perfect concentric circles; sound moves exactly the same way.

So why does an empty room echo and a furnished room does not? It has to do with "reflection". Sound waves will bounce off of a hard surface just as a rubber ball will. When a sound instance occurs in a large space with all hard parallel surfaces such as drywall, plaster, and hardwood flooring, it reflects off of those surfaces back and forth until the energy dissipates. These reflections reach your ear at slightly different times creating one prolonged sound. Drapes, carpeting, and furniture are fabricated from materials that are considered to be acoustically absorptive. That is, they will prevent a certain amount of sound energy from bouncing off of them. The more absorptive material in a space, the less reverberation, or room echo.

Why Should I Correct Room Echo?

Room echo or reverberation is a problem anywhere speech ineligibility is important and overall sound levels need to be reduced, which is pretty much everywhere. Conference rooms, large open office spaces, gymnasiums, houses of worship, factory floors, are all common targets of acoustic reverberation. Without proper treatment, communication is difficult, noise levels are increased, creating an uncomfortable environment. In the workforce, productivity can be greatly diminished.

What's The Solution?

The solution to room echo is to add enough absorptive material such as fabric wrapped acoustic panels to the space to reduce the amount of reflected acoustic energy to levels appropriate for the intended use of the space. Fortunately, in the nineteenth century a really smart guy named Wallace Clement Sabin founded the field of architectural acoustics, and gave us a formula that allows us to calculate exactly how much absorption material to use to come up with a predictable reverberation time. By applying this formula to a material's known absorption capability, (NRC, or Noise Reduction Coefficient), we can reduce the amount of room echo to an acceptable level. Products such as acoustical fiberglass or melamine foam panels have high noise coefficients and make excellent absorbers.



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