Today we’re going to talk about noise. And one of the things about noise that people just don’t understand is it doesn’t really care what you think about it. It doesn’t care what you think about how to stop it. Because I get hundreds, maybe thousands of inquiries every day about “Well I have this noise problem, I don’t know what it is so I built this. I don’t know why I’m building it and I don’t know what the noise is but I’m building something because I have to busy or I have to keep my hands moving.”

I don’t know what the rationale is behind some of these things that I hear but let’s take a step back, slow down a little bit, forget about what’s said in the literature and please forget about this dry wall and green glue thing. If I hear this one more time I’m going to freak out. Just let’s forget about that now and go back and look at the science, look at what we’re dealing with and then I think it’ll come into focus a little bit better.

So noise in our rooms is a 2-way stream. We have our room here, we have noise coming in and then if we’re generating noise we have noise leaving out the room also. So it’s this 2-way valve that we have to be cognizant of. And the walls have to reflect both these types of energy, okay? What kind of energy does it have to be? Well, we don’t care what the frequency is because in a room if it’s a live recording room for example, it’s going to be full range, right? Especially if you have drums.

Now, most noise outside is full range. You have garbage trucks, you have low-frequency generating motorcycles, you have tons of things. You have the guy on his bike with a high-frequency bell going back and forth. What did I hear the other day? An ice cream truck in one of the neighborhoods I was working in and it’s got this PA system on top of the truck and its blasted ding-ding-ding, you know, high-frequency sound.

So it doesn’t matter what it is and what we have to be cognizant of when we’re dealing with barrier technology and noise is the amplitude, the strength and what frequency. Because if our noise is 40 cycles and it’s +10 dB over baseline, that’s a big problem versus 500 cycles at 10 dB over baseline.

So first thing we have to do is we have to measure. We can’t guess. You can’t guess with barrier technology. You can’t guess and use those things that they talk about in the forums that this does this and this does that and without measuring and quantifying. You have to quantify and qualify. You have to know how much and what frequency it is and the barrier that you build is directly dependent on these numbers that you qualify and quantify.

So your construction method is depending on the amount of energy that you have to work with, the thickness of it, the composition, the way it connects to the other walls; all of these variables have to be taken into consideration.

So the noise doesn’t care what you think about how to stop it. I have never in 10 years of working with people on these noise issues, I’ve never come across anyone who’s built the proper barrier to stop the noise that they’re trying to stop. They’ve all made attempts based on what they read in forums and the literature but they’ve never measured, they’ve never quantified and they’ve never qualified. So if you don’t do those two things you’re just guessing. And like I always say, if you guess in acoustics you’ll always guess wrong.

So what are our breakpoints that we need to look at? As a general rule, if your noise is greater than a 125 cycles, that’s a happy problem we call in the business. Because the barrier technology that we have to build for those kind of issues is not as thick, is not as complex, is not as dense, doesn’t have the mass because we’re dealing with shorter wave, shorter wave links.

So less than 125, we all know that that’s the lower frequency energy, that takes thicker barriers, denser materials and a completely different construction methodology than frequency is over a 125 cycles. So as a general rule, this is the breakpoint we use in barrier technology. But it’s very much dependent on how strong it is. That’s how thick the wall needs to be. And at what frequency, that tells us what materials and how to arrange them within the wall.

So the noise doesn’t care about what you think about it, okay? It definitely doesn’t care what you think about how to stop it. So first thing we have to do is qualify and quantify and we can do that through measurement. And we’re going to go over measuring noise in another video.

Dennis Foley

Author Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

More posts by Dennis Foley

Join the discussion 2 Comments

  • T.W. Day says:

    You should probably do some study of the Green Glue wall construction tests before you whine too much about what you don’t get or don’t like. I’d put Orfield Lab’s test capability over some studio rat’s any day. You are absolutely right about physics, though. It doesn’t care what you think.

    • T. W. Green glue is a product name for a simple adhesive compound. There are many others available. It is an adhesive with “magic” powers assigned to it according to company sales literature and widely held belief systems such as yours. Look past the brand name and look at the chemical composition of the adhesive. Then, go into the marketplace and find that chemical composition in other adhesives. You will quickly see the reality of the “chemistry” of the physics and the associated exaggerated claims. There are many other ways to achieve equal and in most cases much better performance with much less cost when it comes to an adhesive application..

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