Existing noise levels inside ambulances can reach 110 decibels, which is the equivalent of a jet taking off 500 feet away. However, Road Rescue Inc. (St. Paul, MN) is the first ambulance manufacturer to offer a noise reduction and soundproofing package to its customers.

Since 1976, the company's products have been designed and built according to individual needs. Steve Saggau, president, explains, "Noise abatement has become an increasing concern among our customers. We're committed to exploring new technologies that would make our ambulances quieter and safer."

The ambulance interiors are composed of aluminum, which is strong, lightweight and does not absorb liquids. Noise resonates through the floor of most vehicles, and to compensate, the company installs 2 inches of 3M (St. Paul, MN) acoustic composite material on the ambulance floor. This reduces noise levels by 20 decibels. As an extra sound absorber, acoustic curtains made from absorbing fibers are placed over the vehicle's wheel wells. Acoustic water curtains are waterproof, and the outer cover is available in either fireproof or fire-retardant materials. Thinsulate acoustic insulation is also placed over the acoustic composite material in the walls and ceiling, adding another layer of soundproofing.

Anodized aluminum cabinets and shelves inside the ambulance provide another challenge for sound abatement. Strips of damping foil 2552, applied to the interior metal cabinets, damp sound and vibration. The pressure-sensitive viscoelastic polymer reduces noise, eliminates the need for redesign and delivers effective damping with as little as 10 percent surface coverage.

When evaluating soundproofing methods, the company was concerned about adding weight to the vehicle. Typically, adding more insulation reduces noise and vibration. However, the acoustic material captures unwanted noise without the bulk or weight. The insulation requires no special safety equipment. Together, these technologies abate vehicle noise with less weight than previous materials.

For more information on acoustic insulation and damping foil, call 3M Co. at 800-362-3550, visit www.3M.com/bonding or Reply 4.