The two primary sources of noise are airborne noise and structural noise. Airborne noise results from the interaction of a vibrating surface with the surrounding air (think of a speaker) while structural noise results from the vibrational energy that travels through a structure, as well as other surfaces it might contact. While the noise from a radio or television might be desirable, other sources of noise from machinery, between floors in a building, or inside our car can be highly undesirable. There are a variety of strategies to reduce and control unwanted noise. Fabricated foam and adhesive parts play a significant role in achieving those reductions.

Airborne Noise

The primary strategies for reducing airborne noise are absorbers and barriers. Lightweight open cell foams are a very cost-effective way of attenuating noise in the air; particularly low frequencies. The open cell structure can absorb sound waves reducing the amplitude of the wave as the sound energy is transformed into heat. These materials include open cell polyether and polyester foams as well as reticulated (cell walls are removed to increase porosity) foams.

 (Open Cell Urethane Foam)

  Low density, closed cell foams can act as both an absorber and a blocker and do better with medium to high frequencies. PVC and low density cross-linked polyolefin foams can be used in these applications. Synthetic blanket materials such as 3M Thinsulate and fiberglass composite materials are also effective solutions for attenuating unwanted airborne noise. These materials can be supplied with a pressure-sensitive adhesive backing to facilitate easy installation and are easy to die cut into the final shape using flat bed, waterjet or flash knife cutters. Low density, closed cell foams can act as both an absorber and a blocker and do better with medium to high frequencies. PVC and low density cross-linked polyolefin foams can be used in these applications. Synthetic blanket materials such as 3M Thinsulate and fiberglass composite materials are also effective solutions for attenuating unwanted airborne noise. These materials can be supplied with a pressure-sensitive adhesive backing to facilitate easy installation and are easy to die cut into the final shape using flat bed, waterjet or flash knife cutters.

Structural Noise

The solutions for structural noise are a bit different. In a manufacturing environment, machinery is the typical source of vibrational noise. In a car, the engine and associated systems are usually the sources. Left unchecked, the repetitive motion of parts and surfaces can result in material fatigue and reduce reliability over time. Isolation is one of the principal strategies to minimize vibrational noise. Dense foams and microcellular foams are ideal material choices for use with heavier objects as these foams decouple the source from surrounding surfaces or housings that would otherwise amplify the sound and vibrations. These materials can be offered with or without adhesive and are easy to die cut for easy application. In some applications, bonding and isolation can be accomplished in one step. The use of acrylic foam tapes such as 3M VHB permit two rigid surfaces to be bonded together (for example a metal building façade panel to a stiffener). Any vibrational energy places the tape into elongation mode even though it is constrained by the two rigid surfaces. (constrained layer damping) The energy is transformed into heat as it damps the vibrations. Another strategy to use constrained layer damping is to apply a thick foil with a soft pressure sensitive damping adhesive such as 3M’s Vibration Damping Foil Tape. The thick foil acts as a constraining layer and the adhesive goes into elongation mode converting the vibrations into heat. Again, these products are easy to die cut and apply. Tom Brown, Inc has the experience to help you address your noise and vibration challenges with a broad portfolio of foams and tape products designed to meet your needs. Contact us today at www.tbi.com.