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Excessive traffic noise is one of the most common complaints among American residents. Millions of people are affected by constant traffic noise in their own home. In fact, traffic noise impacts more people than any other environmental noise source. Traffic noise can affect the ability to work, learn, rest, relax, sleep, etc. Excessive noise can lead to mental and physical health problems. If your home is near a major road or you are experiencing problems with traffic noise, you may be able to limit the impact on yourself and your family.

There are basically four options for controlling traffic noise: constructing (or increasing the height of) a barrier wall, increasing the isolation quality of the home, masking the noise, or controlling the noise directly at the source.

Barrier Walls
Constructing or increasing the height of a barrier wall could result in a noticeable decrease in traffic noise. However, certain guidelines must be met in order for the wall to be effective:

The wall must be solid with no penetrations in order to be effective. Any penetration, opening or gate can degrade the effectiveness of the barrier. Concrete walls are preferred, but other types of walls can also be effective. A barrier does not have to be a wall, it could also be a large earthen berm. A common misconception is that typical landscaping or vegetation can act as an effective barrier for traffic noise. Unless the vegetation is 100' thick and very dense, it will provide very little if any noise reduction.

Typically, a barrier is more effective the closer it is to the source or to the receiver. Noise barriers are generally only effective for homes within 300 ft. of the roadway.

The noise from automobile traffic is primarily from the tires on the pavement. This noise source is at 0' above the ground. Noise from large trucks is typically engine and exhaust noise and is approximately 8' above the ground. In order to be effective, a barrier wall must at least block the line of sight from the noise source to the receiver. Although a 6' high wall can help to reduce auto traffic noise, it will do little if anything for heavy truck traffic. On the same note, if a home is on a hill or elevated above the roadway, a 6' high wall may not be adequate in blocking the line of sight, even for auto traffic.

Increasing the height of an existing wall by 1-2 ft. may make a difference depending on the line of sight issues mentioned above. However, if the wall already blocks the line of sight, increasing the height of the wall by a couple of feet will not provide a noticeable reduction. In fact, the Department of Transportation states the general rule of thumb: each 1 ft. of height added to a wall, above the height that breaks the line of sight between the source (traffic) and receiver (residence), reduces the noise level by ½ decibel (see table below).

Isolation Quality
Traffic noise can also be controlled at the receiver by increasing the isolation quality of the home. Noise is transmitted primarily through the weakest points. Almost always, the weakest points in the home would be the windows. Depending upon the isolation quality of the current windows, upgrading the window assemblies could provide at least some relief. Replacing the windows will not help dramatically if you already have decent windows.

Window isolation quality is expressed as a Sound Transmission Class (STC) rating. The higher the rating, the better the isolation quality of the window. A typical single pane window has an STC rating of 22-25. A typical dual pane window has an STC of 27-32. (See table below). Specialty windows with higher STC ratings are also available.

In existing residences it could be very costly to replace the majority of the windows. Another option that may be less expensive and could produce even better results is to add a window insert in addition to your existing windows. The window insert is placed inside your existing window sill.

Please note that it is important to upgrade the windows that are both parallel and perpendicular to the roadway. It is almost never worthwhile to do anything to the exterior wall of the home, particularly if there is a window(s) in the wall. If the noise does not appear to be transmitting through the windows seek the help of a professional for further options. Contact us for a referral database of acoustical consultants.

Noise can also be masked at the receiver. Sound masking can be implemented outside or inside your home. This can be accomplished by an electronic sound masking system playing white noise/pink noise through noise generators. Other options include, indoor and outdoor water features, fans, or recordings of soothing sounds. However, this is sometimes perceived as adding more noise to a noisy environment. To learn more about masking systems, click here.

Control At The Source
As a resident you may not be able to control traffic noise at the source, but there are ways of limiting problems with traffic noise in the design of future roadways. Traffic noise increases with higher speed limits and with shorter distances from the road to the home. Recessing the roadway can reduce the noise impact. Use of quiet pavement such as rubberized asphalt can also reduce the impact by 4-5 decibels (see table below). Unlike conventional asphalt, rubberized asphalt maintains its noise reduction properties over several years.

Changes in Sound Level, dB
Changes in Apparent Loudness
Almost imperceptible
Just perceptible
5 - 6
Clearly noticeable
Twice (or half) as loud
Note: This chart can also be loosely applied to changes in STC ratings.

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