Airborne sound that is reflected against hard surfaces, for example, a hood over a machine or the walls of a room, can be reduced by covering the surfaces with absorbents on the inside. Materials such as plastic foam, textile fibres, or metal. The sound absorbents convert the airborne sound into small amount of heat energy.
The absorption factor denotes how much of the incoming sound that will be absorbed.
One way to reduce the propagation of noise is to insulate the noise source using a wall or hood. The noise insulation capability of a wall increases as its weight increases. The insulation capabilities can also be further improved by using a double wall system. Insulation pads are available with and without a wear resistant surface.
The Transmission Loss denotes the reduction expressed in dB when the sound passes a wall.
Structure borne sound is vibration in solid materials, generated by a machine, for example. It can be damped by applying a pad on one side or by the sandwich method. In both cases the vibration energy is converted into heat.
The loss factor denotes how much of the vibration energy is absorbed.