Indoor Noise Prediction: From Myth to Reality

This paper is devoted to the general topic of noise prediction in workshops.The intention is not to get into the scienti c details of the methods that allow such a prediction to be made.it is rather to describe why.how.where and by whom this topic was handled.starting from the origins to 1993.This overview is based on the literature available but also and mostly on the experience acquired at I.N.R.S. through 20 years of investigations of various types in the area of sound propagation in workshops and indoor noise prediction throughout this paper abbreviated to INP.Sound prediction in auditoria which has also a long and bright but distinct history is not covered by this paper. 2.THEMY'I'HPractical industrial situations with regard to noise are fon'nidably complex.Machines are among the most intricate sources of sound; acoustical boundary conditions on walls and objects present in a workshop are seemingly untractable considering the infinite variety of shapes and materials.Most basic acoustical phenomena are present and mixed: radiation.specular and diffuse re ection.simple and multiple scattering, diffraction, propagation in closad spaces.With this in mind.thinking of predicting sound pressure levels in a workshop before it is built was a real challenge, However.some acousticians in the world have been brave enough to take it up. HOW THE MYTH wns ATTACKED 3111:: Starting Point}It is of course impossible to state that lNP was invented by Mr. X on day D of year Y. However. the names of RAYLElGH and SABINE can certainly be put forward as those scientists who proposed for the rst time basic equations that describe sound propagation.There is always a potential prediction method behind an equation that links physical parameters together.The whole [NP story lies in between the inverse squared law of free eld propagation and the SABINE description of the pure reverberant eld.The concept of INP was born in the early seventies from the practical need felt by some producers of absorbing materials who wished to quantify in advance how effective their materials would be in situ.FRIBERG's empirical formulas (1) have had a real success and are still referred to by some practitioners.