A room is built to enclose servers, the walls are covered with Peacemaker Sound Insulation which is flexible rubber sheeting.

What is Flanking Noise?

When we’re discussing a soundproofing issue with a customer, we generally spend quite a bit of time describing the phenomenon of flanking sound. This is at the heart of solving many noise problems.

So what exactly is Flanking Noise? Let’s imagine for a moment that you have a wave of water approaching your house. You run outside and install a sandbag wall that is exactly as wide as your property. No water should get through that wall. Next thing you notice that you are up your ankles in floodwater. Why? Because the water simply went around your wall. The water flanked your wall.

This is similar to what might be experienced in a soundproofing strategy. Suppose you share a common wall with a neighbor and he keeps you up at all hours. Perhaps you have an upstairs neighbor that sharpens his bowling skills after midnight. Let’s further suppose that you install 12” of lead on that wall or that ceiling. That should solve the problem, eh?

If you think of our floodwater analogy, it might not come as a surprise that you may continue to hear that noisy neighbor even after a soundproofing treatment. Like our floodwater, some of the sound simply flanked around the 12” of imaginary lead.

Sound will move from one room to another through both direct and indirect paths. Some amount of energy will travel through or around a wall or ceiling.



You might wonder if you should even bother treating just

the wall or just the ceiling at all. Well while every structure is different, treating only the one main “direct” pathway will most often prove satisfactory for most people. This tactic generally reduces the sound to a tolerable level, but will usually not eliminate 100% of it.

It is important to understand that while sound can travel through air pockets like ductwork, stud and ceiling joist cavities, it can also be conducted along studs, joists, pipes, concrete and glass. Like your voice on a string between two orange juice cans. The string is a conductor just like a stud or joist.

A common myth is that if you don’t treat every surface, all of your soundproofing efforts will have been in vain. This is simply not the case at all. If you significantly reduce the sound passing through the one main wall, for example, that’s great. What remains will likely be flanking noise coming through side walls, the floor or some other untreated surface.

MAJOR FLANKING PATHS

Through the floor framing system under the wall. In some construction there is a joist system that travels under the offending wall. The floor systems on either side of the wall is connected, so while there is no open air path from his side to yours, the floor framing itself can conduct the vibration from his side to yours. This may or may not be a significant flanking pathway.

Through the ceiling joist system. There are times when an attic area is common to both rooms. Vibration from the offending room are transmitted via airborne path or conducted through the joists themselves.
Through side walls. Walls in your unit are usually directly connected to the next door unit.

MINOR FLANKING PATHS

Through the Ductwork. How many times have you been able to listen to a conversation going on in another room by sticking your ear by the air vent? Standard ductwork is metal, and therefore very conductive. Ductwork has smooth, hard surfaces and can therefore bounce sound inside from one room to another. Try lining the rigid ducts with a 1” compressed duct liner, generally available through any Heating & Air Conditioning distributor.

Doors. Whether residential or commercial, most doors are poor isolators of airborne sound. Two main reasons for the poor performance. Poor seals and lack of mass. Try a heavy exterior door. It has mass and weatherstrip to seal it up.

Seal up the holes. Outlets and gaps are all holes that can transmit sound, especially high frequencies. Use a caulk where the drywall meets the floor behind the base molding.

Seal the outside surface of the outlet box with a heavy putty pad or use a plastic electrical box designed for use in vapor barriers (they’re sealed).

Seal the junction of the drywall and electrical box with caulk or a foam energy-saving gasket.
Make sure the wall in insulated and that the insulation is tucked in behind the electrical box.
By considering the less obvious pathways that sound can travel, you will have a better ability to stop it. If the situation becomes too much to deal with, you could consider contacting a professional Acoustical Consultant.

Soundproofing Company, Inc

Watch as Green Glue is applied to the back of drywall and then secured to wall for soundproofing.

A 'cloak of silence' for your home may bring relief from noisy neighbors in the future. Scientists have a blueprint to create this cloak and make your home impervious to sound. So they know how this can be accomplished, however they lack the materials to produce this soundproof miracle.

Spanish scientists believe the key to accomplishing this is a new type of composite made out of "sonic crystals". It would work by directing sound waves around an object.

Read


Photo by pasotraspaso

Soundproofing distributors generally cater to the retail customer. That's great for most of us, however a new company is focusing specifically on the contractors among us. The Soundproofing Company was launched in 2007 to offer the industry a consolidated source for core sound isolation products and information. Interestingly, you'll find that they don't offer dozens of materials. They are focusing on just the stuff that works, or as they say, "Noise control for real life." They may have a point. Let's face it, do we really need 6 types of flooring underlayment? Their site has excellent, easy to understand articles and their knowledge of practical soundproofing methods may be their best commodity. The staff previously worked with Green Glue Company, so they likely know vibration damping inside and out. The prices seem to bare out their contractor based philosophy. Their Speedload system with bulk Green Glue in 5 gallon pails is the least expensive way to buy the stuff.

Check them out at www.SoundproofingCompany.com

Tags: soundproofing, soundproof, green glue, speedload system

So here you go, Dave's Top 10 myths in soundproofing, feel free to submit comments to add to this list.


10. You can absorb the sound. The fact is that absorbtion alone will simply not work. There is an exception though, in eviroments such as a sound studio, absorption is used to capture reflected sound.


9. You can cancel noise with a equal and opposite soundwave. This might work for a steady noise like the drone of machinery, but technology just is not ready to cancel out unpredictable noise.


8. Particle board and plywood for soundproofing. No, it will however increase sound transmission.


7. Foam rubber may be good for fish hats, but not so good for soundproofing. The foam rubber will break down over time and is extremely flammable.


6. Carpet will help absorb the noise in your room, however it does not have any value for soundproofing. Keep it on the floor where is was meant to be.5. If your into insane asylum chic, then old mattresses might be your thing. No, not really, they would have to cover every inch of your room and have to be sealed and caulked. I would imagine they would become pretty smelly over time.


4. Blown in cellulose will provide very little soundproofing, wet spray on cellulose may be better.
3. Hay bales are good for feeding your farm animals, but not for soundproofing. However a mixture of mud and hay packed between walls is a different story.


2. Regular old fiberglass insulation batts are good for thermal insulation but not soundproofing.


1. Egg cartons are excellent for eggs, not so good for soundproofing.