If you go on line or to a music store and are seeking room acoustic treatment, both will be happy to sell you foam panels. Foam panels are easy to make and package as room acoustic treatment. They are marketed as an acoustical solution that will fix all your acoustical issues. Foam panels are even marketed as a solution to your low frequency issues even though it takes a piece of foam 11′ thick to completely absorb a 100 Hz. wave. You can even buy a complete room acoustic solution in a box in some stores. Really? That’s really going to solve your acoustic issues? Come on.

Ringy Mids and Boomy Bass

People notice that their room sounds “ringy” and “boomy”. If the room sounds ringy, we are dealing with flutter echo. If the room sounds boomy, we are dealing with low frequency room modes caused by excess low frequency energy. Individuals buy foam or prepackaged “total” studio acoustic solutions and put it everywhere throughout their studio. After the foam installation, they notice that the ringing is gone, but the bass boom is greater than ever. This occurs because there is not as much high frequency information present in the room due to the foam placed throughout the room counter balancing the bass boom. We have succeeded in absorbing the “life” out of the room.

No Solution In A Box

How can this be? The salesperson said that this foam in a box was all I needed to control all the room acoustic issues in my room. The internet said that the foam panel package that I bought was a “complete solution in a box”. First issue is that foam cannot absorb low frequency waves. The second issue is that manufacturers claim their foam products absorb low frequency energy but they consider 150 Hz. to be a low frequency wave. They are mistaken and should be held to task for false advertising claims. Let me be perfectly clear: Foam will not stop any real, low frequency, wavelengths. Foam will not stop any real, low frequency, wavelengths. Foam will not stop any real, low frequency, wavelengths.

Here’s a video our Chief Product Designer and Acoustic Engineer, Dennis Foley, made to help illustrate the point!

Bass Traps

Knowing this, we now go back to the music store or online store and buy bass traps. Bass traps are a misnomer. Bass traps do not trap bass or low frequency energy. Lets be clear here and stay with a low frequency definition of anything below 100 Hz. as real low frequency energy. Even concrete 8″ thick will not stop bass energy. Steel plate will not stop bass energy completely. What chance does a “bass absorber” filled with foam have if concrete or steel can’t do it. The answer is absolutely no chance. Foam bass traps do not absorb low frequency energy below 100 Hz. Most absorb at low, middle, frequencies if anything.

Here’s another video Dennis made to help explain this point for you.

With our new foam bass traps installed we should be happy with the sound. Our middle frequencies do not sound too bad, but we have no highs left in our room because of all the foam we have purchased and spread around our room. Our boomy bass issues are still there and they sound worse than ever. What is the problem?

Every Room Is Different

Every room is different and requires particular attention to that room’s issues. There is no one acoustical solution in a box that will fit all room sizes. There is no way to control low frequency energy with foam panels that hang on the wall, set in the corners, or glue to the ceiling. You must approach the room from the low frequency issues first and then work up through the middle and high frequencies. No box of panels will assist you completely in anything except increasing your frustration level and draining your bank account.

Low Frequency Definition

Low frequencies are any frequency below 100 Hz. Any frequency above 100 cycles can be dealt with panels and foam. Frequencies below 100 Hz. cannot. Frequencies below 100 cycles must be dealt with specific sound absorbing technologies that have the design parameter goal of absorbing below 100 cycles. Low frequency absorbers must have mass and density to stop low frequency energy. They are heavy by design and must be placed in the location where the resonances are occurring in the room. Room corners are a good start. All the surface area that lies at all wall/ceiling and wall/floor room surface boundary intersections. All rooms are different and all rooms have different dimensions that produce different resonances at different locations within those dimensions. There are no solutions in a box or one size fits all when you are dealing with different room sizes and how they react to low, middle, and high frequencies.

In this video Dennis explains this point a little further for you.

Special Technology Needed

The management of low frequency energy within your room takes special low frequency absorption technology. It is technology that is focused on wavelengths below 100 Hz. A 20 Hz.wave is over 56′ long and full of energy. The only type of absorption technology currently available that can handle this type of energy is diaphragmatic absorption. Diaphragmatic absorption can be designed to absorb a lot of energy in a small amount of real estate. It can be made to have high rates and levels of absorption within all frequencies below 100 Hz. Diaphragmatic absorbers that are specifically designed to handle low frequency absorption do not come in a box or can they be hung on the wall. They come on a pallet and need a hand truck to move them and position them in place within the room.

Here’s a further video to help explain what I’m talking about here.

Do Not Need 100 % Absorption

In our room acoustic example of a solution in a box, we had no high frequency presence in our room after we installed all of the foam panels. Why is this? It is because current foams in the marketplace absorb everything that they can within their design parameters. I think their goal is to absorb a 100 % of every frequency they can within their designed parameters. This feat is what they push as their claim to fame. Some of the acoustic foams do this and they do it well. Do we really need 100 % absorption all the time, no matter what the use? We do not.

Smooth Rates And Levels

What we really need is an acoustic foam that absorbs at a consistent and smooth rate/level. It is this rate and level of absorption that is important. We do not need to absorb everything all the time. Once sound energy is absorbed, it is converted to heat and lost forever. Do we really want to loose energy in order to manage it? We want to absorb just enough throughout the foam’s frequency response capacity to effectively treat the room reflections with care and courtesy. We do not need 100 % absorption of anything. We just need to reduce the amount of energy in a smooth, gradual, consistent, and predictable manner that will not take the life out of our rooms and leave middle and high frequencies in our room gasping for air.

In this video Dennis explains this a little further for you.

There is no room acoustic solution that you can buy from a music store or the internet that comes in a box that will solve all of your room acoustic issues. Every room is a different size and has a different use. There is no one size fits all. Start by analyzing the low frequency issues in your chosen room. Look at the room size, speaker location, listening or monitoring position, pressure levels in the room and the room’s volume. Focus on all energy below 100 Hz. Middle and high frequency ring or echo can be dealt with using foam. Choose a foam that has a proper rate and level of absorption with a gradual absorption response instead of one that absorbs everything at 100 % levels. More absorption is better when it comes to low frequency energy, but not for middle and high frequencies.

Questions at the back?
If you have any questions please feel free to contact Dennis on our regular number or email info@acousticfields. To further your understanding of room acoustics and the issues you face I encourage you to sign up for our mailing list as we hold back some of our most insightful videos just for our subscribers eyes only. You can join the mailing list by entering your name in the top right hand corner where you see the red arrows. You will instantly have access to our free ebook “Free Space Listening” as well as a series of videos to help you identify the room mode issues you have in your room and how to deal with them.

Thanks and we look forward to helping you further.
Mike

MikeSorensen

Author MikeSorensen

I am a structural engineer as well as a master furniture maker. I design cabinets for low frequency, activated carbon absorbers. Connect with me on Google+

More posts by MikeSorensen

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.