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Push on Peaks, Troughs Fill

Dennis Foley April 12, 2018 No Comments

Today we’re going to talk about room response curves when we’re going to deal with the peaks and the troughs that we see in our room response curve.

So we all know that our rooms when we measure them, and there’s many ways to measure them but let’s just speak in broad general terms for understanding and comprehension. We know that each room has a signature, just like a photograph, it’s a signature of how the room reacts to sound and pressure at different frequencies, different domains, the time domain for one.

So all rooms have what we call a frequency response curve. And small rooms unfortunately, which is the ones we have to work in for our music, have characteristics to them. And we have a database now of a 140 built and measured rooms and if you look at all the response curves in that database you’re going to see some patterns. And one of the patterns you’re going to see is a peak. And the peak is always less than 100 cycles, in general terms.

So we have this big bump. So what does that mean in terms of the sound equalities to the room, the audio in the room? What does that mean? Well, I think we can safely say that a peak is going to be exaggeration, okay? We’re going to have more than we want at this frequency.

So let’s say for purposes of the discussion that it’s 40. So what this picture or room response curve is telling us is that the room is not happy with this kind of energy. And it’s telling you it’s not happy with that kind of energy and that’s its way of telling you. So when you take a picture so to speak of the energy in the room you’re going to see that it’s really unhappy at 40. Now, what you have to realize is that 40 is composed of the fundamental of 20 maybe in the harmonic of 20.

So we’ve got all of these things going on within the room. And at this particular peak we have to realize that it’s composed of many things. So what’s the major cause? Dimensions. And size. There’s just certain dimensions that certain wavelengths don’t like. And that’s the reaction you get when the room is too small for the wave to fit in. So we see that bump here. Now, they can be high. We’ve got some in our database that are +16 dB SPL. So big, big, big bumps. You can’t EQ that. So we’ve got to manage that and we’ll talk about that later.

Then we have our cousin, the trough, okay? Or as we hear in the literature, the null. Which is an area of void of certain frequencies. So we’ve got too much and we have too little. So we have this constant flow of too much and too little energy throughout the room. And obviously our goal is to try and get something that’s more consistent and more flat where all frequencies are evenly represented.

So how do we balance this craziness out? If we push on the peak. Now, if we push on the peak, we can’t physically do it but we can do it through absorption treatment. We measure what the problems are that are causing the peak and then we put in sound absorption technology step by step which lowers the peak.

Now, if we push on the peak we have to realize that the trough where there’s no energy is the direct relationship to the peak. So if we push on the peak the trough will kind of fill up for us. Because the trough is composed of the harmonics that caused – from the fundamental that caused the peak. So if we manage the fundamental and the harmonic energy that causes a peak our troughs will start to come into balance. And that’s the key. That’s the key always with room design. We always try to balance out the peaks and the troughs.

Do we get a flat room response? We can. We have a flat room response at Sacred Ground, well, plus or minus 1 dB. Pretty flat. So yes, we can do it. But our goal really for most rooms is to try to get plus or minus 3 dB because then you can EQ that electronically. You cannot EQ +16. It won’t sound right, you’ll hear the electronic artifacts from your EQ system. So you have to be really, really careful.

So we have to be realistic. Now, how do we get this to come down? Well, let’s take our carbon technology and this is why I created it. We get about 1.5-2 dB attenuation for every 8-10 square feet of our technology. So we know that if we’ve got a +16 bump and we want to get to +3 we’ve got the work cut out for us. That’s 13 dB.

So if we know that each one of our units does 2 dB, and we’ve got to have a lot of units, see? 6, maybe 10, it depends on the pressure level in the room. So what we have to realize is that we can treat this with predictability and consistency if we have a tool that’s predictable in consistency and its performance. And that’s what our carbon does.

A lot of companies will tell you that foam can manage this. They’ll tell you that their technology can manage that but they’ll never tell you how much it can manage because most of the time it can’t manage much of it. So they don’t want to tell you how bad it is. We’ll actually tell you what our products do and the rate and level of absorption that you get out of each one. There’s no easy fix and you have to give up square footage if you’re going to manage this kind of energy.

So remember, peaks and troughs are composed of fundamentals and harmonics and if we push on a peak, the trough will come up and then we can treat everything a little bit more equally. Hopefully get it down into a range where our electronics will manage it.

This is an unedited transcript from our video series from Acoustic Fields. There will be some errors in grammar and sentence structure that occur during this translation process.

For complete understanding and comprehension, please view the video which is included in this text. For any additional information regarding this topic or others relating to room acoustics, please contact us directly at:

P: 520 – 392 – 9486


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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.Connect with me on Google+

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