Most of us are aware of the dangers of air pollution outside of the home. Every year, we hear of efforts to contain that pollution, protect the environment and preserve the ozone layer. Interestingly, much less focus is placed on indoor air quality, despite the fact that pollution levels are generally two to five times higher indoors than out and can be up to 100 times higher in big cities. Couple this with the fact that Americans spend more than 90 percent of their time indoors, and we can immediately see that our focus must shift to improving indoor air quality if we're going to protect our health and well-being [source: USGBC].
Poor air quality can be caused by mold, dust, off-gassing associated with building materials, radon, carbon dioxide, tobacco smoke, cooking fumes, bathroom exhaust, and simple metabolic processes of humans and animals, where CO2 and other by-products are released simply through breathing.
Most of us will notice when our homes are too stuffy, too humid, or if there's some strange smell we can't seem to figure out. But surprisingly, few of us know that the key to controlling these problems lies with our ventilation systems. In fact, a Seattle-based study done by Ecotope, Inc., revealed that more than 25 percent of people had no idea whether or not their houses were even equipped with a ventilation system. Of those who were aware of their systems, 70 percent had no idea how to use them or how they operated [source: Bower].
While proper ventilation systems are important to our health and comfort, many people are hesitant to use them because ventilation systems can be very noisy. To help combat the noise problems, we turn to acoustic ventilation. This process helps us bring fresh air into our homes, remove pollutants and control humidity levels, all while it is invisible to the ears, eyes, nose and touch. We shouldn't feel air from ventilation systems creating drafts. It shouldn't blow papers off the desk or billow the drapes. We shouldn't be able to smell exhaust fumes or outside odors. And we shouldn't be able to hear the fresh air being distributed through our homes while the stale air is being removed.
To understand why ventilation systems tend to create noise and how we can control it, we must first understand how sound travels and what sound control technologies are available.