Hi everyone, I'm Dennis Foley from Acoustic Fields. Today we're going to talk about sound
dampening materials versus sound absorbing materials. These terms are used interchangeably and they're
really not. They pertain to completely different things, completely different concepts and
mechanism; related but really different and there's a lot of confusion in it. Let's try
to clear some of that up today. Sound dampening materials, the operative word
here is dampening. Dampening is really a vibrational term. We damp vibrations. Remember the rock
on top of an amplifier? It got better sound, well it got different sound because that's
an electromechanical system and you put some mass on it, you change the vibrational signature,
sort of speak of the unit. Damping is a process that's relegated to vibration and the science
of vibration. Damping is a process we use in barrier technology. When you build a real
nice recording studio, you have 2 rooms really within one room. You have the inside room,
which is where you use your sound absorption and sound diffusion treatments and you have
an exterior shell, which keeps the noise from the neighborhood and surrounding areas out,
keeps the base drum and guitar and electric guitar from coming out of the studio also,
hopefully. Damping is a vibrational term used in vibration. We want to keep those 2 separate
but distinct. Really when we're talking about, instead of
saying sound damping materials, we should say, and people think that sound damping means
sound absorption. It does not. Sound absorbing materials should be called sound absorbing
materials and sound attenuation is the process whereby you use that sound absorption to reduce
the energy levels but sound damping and sound absorption are different, very, very different
and let's look how. Let's use an example to illustrate sound damping.
We discussed the 2 rooms that we have really in our studios that we build. We have the
inside room and then we have the outside shell. The outside shell is really the barrier between
outside noise coming in and inside noise going out. In that barrier technology, we use a
lot of times multiple layers of materials, multiple layers with different densities.
Why? Why different densities? Because what we're trying to do is trick, if you will or
fool, to apply human terms to it. This huge pressure wave that the bus outside or that
garbage truck has produced and this wave is headed into our studio. How are we going to
stop it? The quickest way to stop it is through an erected barrier, between it and us. The
barrier has to be selected based on frequency, space requirements and obviously budget. Barrier
technology is very expensive. It can go $350, $450, $550, $100, $550 a square foot in some
cases. Barrier technology, keeping unwanted noise out is very, very expensive to do and
to do it right, especially if you have low noise requirements for the room you seek.
How do we do that? How do we do it in the best way? Obviously we want to achieve the
most impact in the smallest amount of space and obviously not have it weigh very much.
Well we can't satisfy all those criteria so it's going to weigh a lot. We use multiple
layers and the layers of materials that we use have different densities and that as a
vibration, if you're a vibration or a sound energy wave striking this surface and you
encounter one density, it's going to distort your wave form X. When it strikes a material
of another density, it's going to do X plus that material. When it strikes another material,
it's going to do X plus that material. It's this series of materials that the energy wave
has to go through so that it's reduced in amplitude on the other side. There's actually
a name for that process. It's called constrained layer mass damping. I know that's a mouthful
but basically it's the arrangement of materials. It's the choosing of densities. It's the arrangement
of those materials with those densities that causes this huge wave to be reduced into something
that's not so bothersome or troublesome. Damping technology is really associated with
vibrations and we should really keep it in that domain. Sound absorption technology is
really that. It refers to the process of absorption that's converting to heat. Damping really
refers to vibrational control. Thank you.