3 Basic Principles Of Sound And How To Reduce It

Updated 7/20/2014- see video at the end of this post.

Back story; With all the work I have been doing ripping up, and ripping out and putting stuff back together, which I love doing by the way, I have wreaked havoc on my neck, shoulders and  back.  I thought to my self… self, you need to get a massage and see the chiropractor.  So I did.

Dr Kristin in absolutely wonderful and my massage therapist, Michele…well let’s just say I am glad she does not live next door, if she did I would be in the poor house because I would be over there every day!

One of the main elements of a massage is the quiet, low light ambiance that helps a client to relax… not so much yesterday.

They are doing a restaurant build out of the adjacent unit in the plaza where Dr. Kristin’s office is. It had gotten so noisy in fact, she said, they had to switch the massage rooms with the adjustment rooms on the opposite side of the office. While I was checking out, she asked “What can I do about this noise, is there a way to soundproof the wall?”

 

How to soundproof a wall

Before you try to soundproof  it would be helpful to understand some basics about sound and to understand that the term soundproof (IMHO), is a misnomer. Although I use the term here for simplicity, it should really be referred to as sound deadening/dampening.

 

3 Basics of sound

What is sound?

Sound is a vibration or wave, started by some mechanical movement like knocking on a door, yelling into a room, electrical impulses through a stereo speaker, or in the case of my doctors office, hammering on the wall.

 

ripple effectHow sound travels

Sound travels through mechanical waves. A mechanical wave is the disturbance of a medium or matter…
a vibrating object that in turn vibrates adjacent matter causing the wave. Think of a ripple effect in water.

 

To sound proof or sound deaden you need to reduce the vibrations.

Behavior of sound in a room

Sound can travel through any interconnected partials; that is why it can travel through air, water and solids. When sound travels in a room, some of it travels directly to the listener and is called direct sound. The rest strikes the walls, ceiling, floor, and furnishings where some of the sound energy is absorbed, some is reflected back into the room and the rest is transmitted through the surfaces to the adjacent rooms.

Now we know how the sound gets to the doctors office.

 

How to minimize sound travel

Tin can phone

Since sound is a vibration, one way to minimize it is to reduce the solid pathway it follows.

 

For example, remember as a child when you tied two soup cans together with a string to make a phone.  The string was the solid pathway that carried the sound from one can to the other, cut it and you “decouple” or disconnected the pathway and the vibration stops.

 

Decoupling

Decoupling the walls is a fairly inexpensive and pretty effective way of deadening sound. This can be most effectively done by building a double wall with at least a one inch gap between them. By doing this you limit the amount of direct solid surface the sound uses to travel. Another way that is good, but not quite as effective is a staggered stud wall. This method, while limiting the wall surface contact, still allows the sound to travel through the common base and top plates of the wall.

interior wall frame

Sound Absorption

When a sound vibrates a wall, it also vibrates the air  trapped between the surfaces.  The air in the wall will resonate and transfer the vibration from one wall (drywall) surface  to the other.

One way to reduce the air vibration is to add insulation.  Although not greatly effective by itself, fiberglass insulation will provide some absorption. When used in conjunction with wall decoupling
it becomes substantially more effective.  There are also sound boards on the market, although a bit more costly, they are made specifically for reducing the transfer of sound and again, these should be uses in conjunction with a decoupling method.

 

Mass

As mentioned above, for sound to transfer it has to move or vibrate medium or matter aka- the wall. As most of us know the heavier an object the harder it is to move, thus, a heavy wall requires more vibration to move.  One of the more common ways to increase mass is to add extra drywall.

A typical wall is covered with one layer 1/2 drywall. For sound deadening you may want to increase the drywall  to 5/8″ and then add a second layer, in effect making the drywall 1-1/4″ thick.

 

End results

It is difficult at best to completely “soundproof” a room or office, but, by using these three main techniques, you should be able to reduce the noise to an acceptable level.

If you need even more quiet, there are additional steps you can take such as using special polymers and clips between layers of drywall. You may also want to analyse and reduce flanking or indirect sounds that come through areas such as air conditioning ducts, air space under doors etc.  The quieter you need an area the more extreme techniques you will need incorporate into your sound deadening project.

 

Until next time…

 

Life is simple…enjoy the quiet!

 

PS… here are some additional resources

National Council of Acoustical consultants

Soundproofing Company Inc.
 
PSS…7/20/2014- I just received an email on a new Certainteed product called SilentFX Gypsum Board. It looks like a great product.  Check out the video below and let us know what you think!