Science of Noise

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Automotive Acoustics 101; The Science of Noise

Boom Mat’s lesson to have a quieter ride

Every vehicle has a unique acoustic signature caused by its engine type, exhaust, tires, build quality and any combination of aftermarket accessories. That signature sound may manifest as excessively loud wind or road noise, squeaks, rattles, engine noise or more.  This primer explains some of the science behind automotive acoustic products and gives some useful tips on how to address undesirable noise in your vehicle.

Most everyone understands that sound is a vibration that propagates through a compressed media such as air or water. Graphically, a given noise source can be illustrated on an x & y axis, with x representing the decibel level or dBA, and y the frequency range from 100Hz to 5000Hz. With proper sound measurement equipment it is possible to visualize the sine wave of the noise measured.  The loudest frequency level becomes the peak frequency. Controlling this peak frequency provides the greatest benefit for noise (dBA) reduction. This is also where the term, “dB’s for dollars” comes into play. The quieter the desired goal, often the more it will cost. Automotive noise is typically concentrated in the lower frequency spectrum in the 500Hz range or below. Lower frequency issues can also be the toughest to control.

To mitigate and control noise it often requires a combination of noise control materials and composites that will seal, damp, absorb or provide an effective barrier to reduce peak and low frequency sound waves.

Consider first completing an inventory of your vehicle. Are there holes and leaks that need sealing, or is there obvious structure born noise? Make a list of where the noise is originating and then determine the best possible product for the problem area.

Sealing

For holes and leaks, sealing is the first and least expensive option. Confirm all weather stripping is intact and working properly. Search out openings in areas such as the dash, firewall, transmission tunnel, mechanical linkages etc. Holes, gaps or leaks once identified can be treated with caulk gasket material, or Boom Mat Vibration Damping Material.

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Boom Mat Vibration Damping Material can be cut to fit small spaces to seal open holes in the floorboard, trunk and other locations where outside noise is an issue.

Damping

Lower frequency problems and issues can be the result of structure born noise that would benefit from damping. For example, if you rap your knuckle on the side of a metal file cabinet or washing machine, you’ll notice as a result a distinct ring. Damping products are designed to remove the metal “ring” sound, and are typically used in the doors. Damping material can also give a solid thud sound when the door is closed, much like the sound of closing a refrigerator door. Consider damping treatment also for floors, trunk lids and roofs.

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Boom Mat Damping Material is ideal for use on interior locations to reduce structure borne noise. The strong adhesive backing is unaffected by extreme hot and cold temperatures.

Absorber

For peak frequency absorption, sound absorbing material is ideal as it provides a positive end result while being cost effective.  With some automotive interior designs, there is not much room. However, when considering a major noise source, the engine compartment is a very viable candidate for absorption material such as under hood materials. Here, the choice would be for as thick a foam absorber as possible. Strategically placed absorbers in an engine compartment will yield a measurable reduction. Vehicle interiors also benefit from sound absorbing materials used on firewalls, floor boards and roofs to absorb unwanted noise and as an added benefit insulates your interior from unwanted heat while making your interior more quiet and comfortable.

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Under Carpet Lite™, (UC Lite™) from Boom Mat is a ½” thick multi-layer, high tech composite material designed for sound absorption and thermal insulation in interior locations.

Barrier

Acoustic barriers provide the most practical and effective noise control solution in most automotive applications for controlling lower frequency noise issues. Boom Mat’s Under Carpet has additional mass of 1lb. per square foot to deflect unwanted noise from entering the automobile cabin. Considering the top three major noise sources; engine, tires & exhaust, an effective barrier material can be applied to cover the entire firewall, floor pan and rear bulkhead blocking the noise from the source. The effectiveness of the barrier is enhanced with a foam de-coupler (1/4” thick open cell foam) under the barrier to simulate what is called ‘the double wall effect’.

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Boom Mat Leather Look Sound Barrier on a vehicle’s rear bulkhead in the trunk area blocks unwanted noise from the road resonating from the exhaust and through the suspension.  

Boom Mat offers a complete product line to improve acoustical and thermal insulation for a quieter, more comfortable ride.  For more information on Boom Mat products, visit: www.BoomMat.com, call 800-264-9472 or e-mail: Sales@DesignEngineering.com.

About Boom Mat

Boom Mat is the acoustical insulation and sound deadening brand for Design Engineering Inc. (DEI). DEI is a major U.S. manufacturer and supplier of high performance automotive aftermarket products selling worldwide to a large number of commercial markets. www.designengineering.com

 

About Leslie Allen

Leslie (Maxwell) Allen has over 30 years of providing marketing and PR support for companies coast-to-coast, small to large companies that specialize in three major industries: Automotive Aftermarket, Heavy Duty Aftermarket and Powersports. Over the years, Allen has assisted with copywriting for award winning campaigns, developed marketing and PR campaigns and developed and executed events attended by thousands of people. Wildcat Communications is a cost effective way to build more exposure and increase brand awareness.

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