PREDICTION OF RAIN NOISE IN BUILDINGS USING EMPIRICAL MODELS FOR ARTIFICIAL AND NATURAL RAINFALL

The use of lightweight roofs and roof glazing can lead to problems with rain noise inside buildings that interferes with speech intelligibility, acoustic comfort and listening conditions. Laboratory measurement procedures are described in ISO 10140 using artificial rain. Such measurements can be used to compare individual roof elements with a specific type of rain, usually artificial ‘heavy rain’ because it generates sufficient levels above background noise and it can be seen as a ‘worst case’. The artificial rain is defined by a single diameter drop size at a specified rainfall rate. However, it is not always clear how to interpret laboratory rain noise data that has been determined with a single raindrop diameter and rainfall rate in the context of natural rain (i.e. real rain). This paper discusses empirical models that have been developed to determine the time-dependent force on horizontal and inclined plates with artificial and natural rainfall. This has allowed the calculation of conversion factors between laboratory measurements with artificial rain to other situations with natural or artificial rainfall, and between measurements on roof elements that are inclined at different angles.