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The terms Rockwool in acoustic treatment should never be used together. Rockwool or building insulation is designed for BTU retention or heat and cold temperature management. It was never designed for a sound absorption process. The design parameters are cost-effective for keeping your house warm or cool, but they destroy middle and high frequencies when it comes to music and voice. Not only are the rates and levels of absorption horrible for critical listening environments, but the material is also toxic with fibers that are air born and they get into your lungs. You do not have to believe me, just look at the installation instructions. The handling instructions dictate that respirators and full body suits be used when handling and installing the material type.

Music And Voice

Music and voice are different than noise. People confuse these issues all the time. Building insulation is noise technology. It was never designed for music and voice. It was designed to keep your house warm and cold. Using Rockwool in acoustic treatment is like using a wet blanket to cover up with. It will smother the middle and high frequencies with overabsorption. Building insulation is noise technology. It is designed to absorb as much energy per square foot as possible. It does not have any regard for the proper rates and levels of absorption for music and voice. Music and voice are comprised of fundamentals and harmonics. Using Rockwool in acoustic treatment will over absorb the harmonics for music and voice. It is in the harmonics that we find our emotional connection to music and voice.


Rate And Level of Absorption

Music and voice require special rates and levels of absorption and Rockwool in acoustic treatment will not honor those required rates and levels. You would know this to be true if you have ever been in a room where Rockwool in acoustic treatment is used throughout the room. Music and voice require a linear absorption rate. You must have absorption coefficients that are smooth and linear in their progression as they move up in frequency. The frequency area from 125 Hz. – 250Hz. is the first critical octave band that we must get correct from the beginning. Our next task is to then move up to 500 Hz. in a similar linear absorption manner so everything is smooth and linearly. Music and voice rely on fundamentals and harmonics to communicate their emotions. We must treat the fundamentals with the proper amount of absorption but more importantly, we must treat the harmonics with even more respect.

instruments instrument chart

Fundamentals And Harmonics

We have both fundamentals and harmonics when we speak of music and voice. Let’s use numbers to illustrate this concept. If we have a fundamental of 40 Hz. we know that its harmonics are 80, 120, 160, 200, 240…… This is why it is so important to treat the low-frequency energy within your room first and foremost. If we treat the fundamentals first, we have less frequency and amplitude issues to deal with “down the road” as we move through the middle range frequencies where our vocals exist. Remember that our emotional connection to music exists within the harmonics. We must not use absorption technology that over absorbs our middle range frequencies. If we do, then we lose the emotional connection to our music. Using Rockwool in acoustic treatment will ensure that you lose the delicate harmonic balance in music and voice. Once you over absorb music and voice, it is gone forever.

Fundamentals vs. Harmonics:

Absorption Process

Absorption is created by air flowing over a surface. When air that contains sound flows across the surface area of our sound absorption technology friction is created. The process of friction creates heat. heat is an energy change or transformation. With an energy transformation from air-born to heat, we have sound loss occurring. With this loss by energy transformation, we can never recover the sound or emotional connection to our music. Once sound energy is absorbed it is lost forever and can not be recovered. This is what happens when we use Rockwool in acoustic treatment for our rooms. It lacks the proper rate and level of absorption to address the issues we require with our music and voice. We can not afford to lose any fundamental or harmonic energy if we want to connect emotionally to our music.

Image of Acoustic Foam sheets

Open Celled Foam

The most economical way to treat middle and high-frequency issues is with open-celled foam. Open celled foam is designed to have open cells that absorb sound energy. It is not toxic and will not emit fibers that can get trapped in your lungs and produce cancer years later. It is available in different thicknesses to deal with different frequency ranges. It can be cut to fit different installations and covered with fabrics of different colors and textures. It is lightweight and can be easily installed overhead in large room situations to manage reverberation times. You have to be careful with the foam type you choose. Most foams in the marketplace are designed for noise. They absorb as much energy as possible per square foot. They are not designed for music and voice. Music and voice are different and require rates and levels of absorption to avoid absorbing too much energy and draining the life out of our music and voice. Stay with a foam technology that is specifically designed for music and voice.

Acoustic Foam – StudioPro

About Us At Acoustic Fields:

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.

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