A technical and commercial analysis of the manufacture, supply and properties of noise control foams.

Plastic foams are used extensively for the reduction of unwanted noise. With recent changes to the types of foam available and the market for sound absorbers it is possible that a large increase in demand for cellular plastic will occur. By understanding how a foam absorbs sound, methods of increasing performance for a specific application can be suggested.This work investigates how changes in market forces affect the demand for acoustic materials. As alternative materials can also fulfil any new demand, the way in which foam manufacturers are utilising market changes is investigated. The primary factors influencing changes in the demand for acoustic absorbers are technological developments, legislation and public opinion. In recent years there has been an increase in the types of foams available to compete for the noise control market. The newer, high performance, foams have properties which overcome the disadvantages that foam has relative to its competitors. Properties and performance of high performance foams are reviewed.A number of parameters in a foam control its sound absorbing properties. By holding all but one of these parameters constant it is demonstrated how changes have an effect on acoustic absorption. With information on how individual parameters influence acoustic absorption behaviour the possibilities of tuning a foam to a specific application is investigated. The investigation is conducted using models suggested by several authors. Only one model is found to be applicable to cellular plastics and there are limitations to its application.Increased demand for acoustic absorbers and an understanding of how foams absorb sound would indicate a large increase in the demand for acoustic foam. Due to economic reasons the implementation of technology can be too costly. Using foams in preference to other, usually less expensive, materials requires a transference of information to end users. There appears to be a shortage of expertise in the foam industry to communicate this cost justification. Potential for improvement of foam performance for specific application is possible. Equally possible is an increase in foam production brought about by greater demand for acoustic absorbers. In the next few years observation of the industry will reveal whether potential is translated into profit.