Abstract
This paper discusses the directional properties of sound emitted from a large inclined metal-clad roof surface. An opportunity was recently presented to measure the sound emission from a particularly large ribbed galvanised steel roof deck with a very loud broadband noise below from many noise sources. In 37 years of practice, the author has not been presented with a better opportunity to quantify the directivity of sound from a flat roof surface. Measurements were taken at 0.5 metres above the roof and at distances of 10, 50 and 150 metres from the lower edge of the roof. The sound power level of the roof was establishedfrom the close proximity measurements and simple surface area calculations. The level of noise emission from the roof was calculated at three noise measurement locations to determine the horizontal “directivity” of the roof noise emission. Its directivity was found to be related to the energy vector in the direction of sound propagation.