A short test method for sound insulation measurements between dwellings: Dissertation

Principles for the short test methods of sound insulation are reviewed and three actual test methods are analysed.They are divided into two basically different types.One is characterized by the use of only A weighting in sound pressure level measurements, the other includes also C weighted measurements.A mathematical model was constructed for both types of method.The model describes the actual measuring procedure and clarifies their differences.The (incident) source room spectrum was extended to include mathematically also the frequency dependence of the receiving room absorption.Thereafter, short test results could be studied by varying the extended spectrum only.Tests with real data showed that the method using also C weighting was superior to the A weighted method.A close connection was seen to problems in assessing hearing protectors for different types of spectra.The chosen spectral representation and manipulation yielded a new equation for hearing protector use, different from earlier statistical estimates.Finally, effects of the applied frequency weighting on short test results are discussed.Replacing the A weighting by the weighting of ISO 717 1982 or vice versa had no great effect on the test results.The choice between these weightings was shown to be also generally of secondary importance in the acoustical rating of structures.A specific sound reduction index was introduced and defined as the ideal result of the short test method.It was compared to the conventional sound reduction indices and deviations within the reference material were practically insignificant.But generally, the conventional indices were found to be obscure as to their physical and perceptual basis, and studies were carried out to see how the use of a physically better quantity instead of the former indices would influence the acoustical rating of structures.