In a recently completed Bureau of Mines study, the effect of oil and water on the absorption coefficient of 16 different acoustically absorptive materials was investigated. The most common materials such as fiberglass, mineral wool, and urethane foams were found to suffer a substantial degradation in performance at mid-to-high frequencies. However, anomalous behavior was observed in the high density fibrous materials when exposed to oil; in contrast to an expected reduction in the absorption coefficient, a significant improvement at low frequencies was measured. This paper describes work undertaken to further investigate this unexplained effect, as well as the effects of other physical agents.
Proc. 1988 Nat. Conf. on Noise Control Eng., West Lafayette, Indiana, June 20-22, 1988, Pp 267-272