Noise Absorber Foams

Noise
Noise can be explained as any unwanted or unpleasant sound regardless of its intensity or duration. Noise originates from a sound source and is transmitted to the human ear. Sound can be differentiated into two: one that travels through air and the other, through solid objects. The latter can be defined as structural-borne sound.

To control noise effectively, it's important to distinguish between the two types of sound and the medium in which it propagates. Sound waves are a form of elastic waves that occur in any medium that has mass and elasticity. When mass (inertia) enables disturbed particles to transfer energy to the adjacent particle, elasticity enables the disturbed particle to get back to its original position, like a spring. This propagation of momentum from one particle to another explains the manner in which sound waves travel.

All materials with mass and elasticity allow sound waves to propagate within it. This results in the vibration of the object. When the object vibrates, the air and particles surrounding it vibrates. This starts a chain reaction which, in turn, enables sound waves to propagate. These waves produce variations in the ambient pressure and it is this pressure variation that reaches the listener's ear as sound or noise. The ear drum is sensitive to the pressure variations produced by the vibrating particles. Structural-borne sound functions similarly as airborne sound, except the particles that vibrate in the chain of vibrations happen in the medium that propagates the sound. As the mass and elasticity of each medium varies, the properties and the speed of the sound waves will also vary.

When the frequency of the sound waves increases, its length decreases. Or in other words, the wavelength is inversely proportional to the frequency. Usually, it is easier to control noise in the higher frequency bands than the lower frequency bands as it is difficult to absorb sounds of longer wavelengths.

Noise Absorbing Media

A polyether based FPCP media is an ideal material that absorbs both airborne as well as structural-borne sounds. When sound waves that travels through air pass through a porous open cell foam media, the movement of air through the strands and membranes generates heat through friction. This heat takes away the energy from the sound waves which results in the dampening of the noise before the sound exits the depth of the FPCP media.

The Noise Absorber Foams manufactured by MNR can be cut to any shape, size and thickness. The proprietary 'Hot Roll Lamination' process, developed by MNR, helps in applying different kinds of skin to the foam surface.

The technical specifications of the Noise Absorber Foams (20mm thickness) are listed here.

Listed below are the Noise Absorption Coefficients for different thickness.

The skin absorbs low frequency noise and protects it from hot oils, vapours etc. The foams can easily be applied to the substrate of choice, on site, by removing an optional release paper. The pressure sensitive glue provided comes in various strengths measured in PLI (pounds per linear inch) ratings. MNR helps customers in selecting the type of adhesive, backing, and the quantity of the adhesive to be used.