Maybe your neighbor told you that you needed sound absorption panels in your home theater and you didn’t want to ask.

Maybe you have a big echoey office with lots of people working in it and the boss told you to go buy some Sound Absorption and then jetted off to Tahiti without further explanation.   It happens….that’s ok, because I’m here to help.

The easiest way to understand this is with an analogy:

An ocean wave comes in off the ocean, rolls in and hits a big flat concrete storm wall, its going to bounce right off of it and head back out to sea looking just like it did coming in.   That is what a reflective panel would do, or drywall would do, or concrete…or anything hard and flat would do to a sound wave.

Now say a wave comes in off the ocean and hits a marshland with a bunch of reeds and grasses and muck.  The wave is going to hit all those hundred billion little things which move around and dissipate its energy nearly completely and so the wave disappears.  That’s what an absorptive acoustical panel will do to a sound wave.

That’s about it.

NRC rating

I can’t just leave it at that though, if you’re so inclined to learn more, lets continue! X amount of sound hits the panel, and then a smaller percentage of that sound reflects off.   How to compare apples to apples in terms of different Acoustically Absorbent Materials?  Absorptive things in the world have a number called the NRC rating, or the Noise Reduction Coefficient.  It’s kinda like the Octane rating on gasoline, or the Proof rating on alcohol, it tells you how potent a thing is.  Acoustically speaking the only thing that matters to the sound wave is the NRC rating, it doesn’t matter to the sound what an Absorptive panel is made of or what its wrapped in or any of that stuff.  There is no guess work with this, the NRC rating is the NRC rating.    For instance, an NRC rating of 0.75 means that 75% of the sound is being absorbed (as averaged across the frequencies, more on that later)  and 25% is being reflected back.  NRC 0.85, 85% absorbed, 15% reflected.  Etc.

Frequencies in sound are just different tones.  Middle C on a piano is about 261 Hz.   People speak at about 500 Hz.  Subwoofers are usually 20-200 Hz.   Thicker things absorb sound at high and lower frequencies.  Thinner things only absorb sound at higher frequencies, generally speaking.

Check out the Data Sheet for one of our AlphaSorb® Fabric Wrapped Wall panels now and see if it makes more sense.

Techy info coming up, Warning!

NRC ratings of greater than 1.0 are possible because NRC rating is trying to give a 3-dimensional thing an impossible 2-dimensional number.  If something has an NRC rating of 1.15 for instance, it obviously cannot absorb 115% of the sound that hits it.  The answer is:  It’s a computer programming thing.   When they write programs to model 3-D rooms, it’s much easier to program for impossibly absorbent 2-D things on walls of a 3-D model, than it is to model a real 3-D absorbent thing on a wall in a 3 D room.   From that need has spawned impossible ratings as the “convention” in acoustics when speaking about the specific absorbency of something.   Trust me, if we rated them in “Sabins” this discussion thread would be much longer.

And now the most important thing to remember:

Acoustically Absorbent panels DO NOT stop the sound from going through a wall.  They are for reducing echoes within the room they are placed in, only. Things that STOP sound from going through a wall have an STC rating.   This is entirely different class of materials utilizing much different principles of physics to block sound waves.   I will have a different blog covering that topic soon.

From here, one could make the leap to: “Well OK, but how many panels do I need then?” That’s a little more complicated, but not too much.  Your best bet for that would be to go ahead and get the measurements of the Length, Width, and Height of the room in question and shoot me a quick email with the info.  Based on that I can run a model and shoot you back the results with a quote for materials.

Well, I hope you enjoyed reading this blog as much as I loved typing it!  Thanks!