Determination of The Scattering Parameters of Fittings in Industrial Buildings for Use in Computer Based Factory Noise Prediction Models: Part 1 – Theoretical Background

In this the first of two companion papers, it is established that the accepted view amongst researchers is that models in which the scatterers of sound in industrial buildings are defined in terms of a mean scattering cross section and absorption coefficient are the most accurate. At the present time there exists no method of determining these parameters. From consideration of the behaviour of sound in a proportionate live room (reverberation chamber) it is shown that the scatterers with a low mean coefficient of absorption the product of mean scattering cross section and absorption coefficient is equal to one quarter of the effective area of absorption of the fitting.

The results of computer simulation employing the RAYSCAT model suggest that, although individual values of the two parameters are required as input data, it is actually the product of the two parameters which determines the sound propagation characteristics of a room containing scattering fittings. The results obtained from further simulations suggest that if the equivalent area of absorption of fittings is known, then the sound propagation characteristics of a room containing those fittings can be predicted to a high degree of accuracy by employing an estimated a value of mean absorption coefficient and a value of mean scattering cross section calculated as equal to the effective area of absorption divided by four times the estimated value of the absorption coefficient.

In the companion paper which is to follow, the validity of these hypotheses is examined by means of measurements made on acoustic scale models.