We live in a noisy world. Noise seems to be everywhere - traffic, construction, loud music, crowded buildings. Noise can even be a problem in labs and offices. The problem has become so wide-spread we have even created a term for it: noise pollution. It may not be possible to stop all that noise, but thanks to advances in technology, there are ways to isolate ourselves from it. To understand how we can begin to isolate ourselves from all that noise, we need a basic understanding of how sound travels - not just through the air, but through walls, floors and ceilings.



Sound travels through the air in waves, and those waves cause the objects they come into contact with to vibrate. When a sound is loud enough, those vibrations can travel through walls, floors and ceilings transferring sound into our buildings from the outside or from room to room and floor to floor on the inside. The key to effectively stopping unwanted noise from invading our space is to stop the vibration.

In most homes and commercial buildings, walls and floors have an interior support structure of wood or steel studs or joists and are covered with some form of rigid sheeting like drywall or particle board flooring, leaving an air space between the walls, floors and ceilings. That air space allows for the easy transfer of sound waves with very little solid mass for the sound to vibrate through or slow its transfer. One of the most common methods used to reduce the transfer of that sound has been to insulate the wall, floor or ceiling with one of several types of insulation. This may reduce the transfer of sound vibrations through the air space, but does nothing to stop the sound transferred through studs, drywall, joists or flooring.

It's also important to understand that not all sound frequencies are not the same when it comes to insulation. Lab tests show that low frequency sounds aren't stopped by insulation, and high frequency sounds aren't reduced significantly. Insulating the air space is only effective in deadening mid-range frequency sound.

Then how is sound transferred in an insulated wall? When drywall is nailed directly to wall studs, sound waves vibrate the drywall, that vibration is transferred to the stud, and is finally transferred to the drywall on the other side of the wall. That vibrates the air in the room and the vibrations become sound waves again. The industry calls this coupling.

One method to reduce this transfer of vibration is called de-coupling. De-coupling is nothing more than creating a space between the drywall and studs. This dampens the sound. That is, the vibration and resulting transfer of sound is greatly reduced. This can easily be done during construction by placing a resilient cushion between the drywall and stud to absorb the vibration. There are clips and channels available for that purpose. Another even more effective method is to install a cushioning sheet over the stud wall and under the drywall, or over floor joists and under sub-flooring, When combined with insulating the air space between walls and floors, there is a significant reduction in the transfer of high, low and mid-range sound frequencies.

It is also important to seal around all outside door and window openings with a good quality caulk. To reduce the transfer of sound from room to room, don't forget to seal outlets and install duct liners in furnace and air exchange duct work. When used together, each of these methods will go a long way in controlling the transfer of unwanted sound.

So far we have considered reducing sound in a home, a commercial building or a single room or area. And these methods are really only practical for new construction. They also can't completely eliminate sound - only reduce it to acceptable levels.

What can be done when retro-fitting a room isn't cost effective and sound isolation is needed? The answer may be as small as a portable “mini” sound shelter or as large as a sound isolation room. There are any number of applications where sound isolation is required. Hearing testing, speech therapy, psychological testing and data recording and industrial applications are just a few.

To meet those needs audiometric booths, sound isolation rooms and noise reduction rooms are available. By incorporating innovations like carpeted vibration isolated floors, space-saver roof mounted ventilation, recessed electrical outlets, noise-lock doors, double glazed windows and double thick modular wall panels, sound can be controlled in small spaces such as a portable booth or as large as a room within a room.

Understanding a bit about sound, how it travels and what can stop it can help you decide what you need to do to control the sound around you. Whether you want to keep the noise of the outside world out, quiet a part of your home or commercial building or need an area of sound isolation, understanding the technology that is available can help you make a sound decision.

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