Keep that noise down!

Pressure-sensitive adhesives provide an economical way to control noise and vibration. Appliances, such as refrigerators and computers use pressure-sensitive adhesives to control noise. Foam sound absorbers disrupt sound waves and absorb vibrating air molecules. Sound barriers block sound waves from transmitting. Free-layer damping adheres a semirigid material to a vibrating source. In constrainedlayer damping, a viscoelastic material is sandwiched between a rigid material and a panel. Squeaks, rattles, and hums are music to an appliance designer's ears. These nuances, specifically those caused by vibration or the friction between two dissimilar materials, can be controlled with the use of pressure-sensitive adhesives (PSA). In dry or solvent-free form, these tapes are permanently tacky at room temperature. They can be used from simply bonding plastic foam to metal panels all the way to specialized vibration-damping applications that rely on the viscoelastic properties of certain adhesives. Any fastener selected for sound abatement must be done with the surroundings in mind. The fasteners must work with the appliance environment, which can range from hot, dirty motors to machine panels and cannot add sound. Mechanical fasteners can be used, but must be engineered into the design. They are not easily changed. Glues often require special application equipment as well as time to dry. PSA's on the other hand, adhere to surfaces with finger or hand pressure and don't require activation by water, solvent, or heat. Proven devices for sound and vibration control include sound absorbers, sound barriers, antifriction films, and vibration dampers. PSA's play an active role in each. Sound absorbers trap the