Demonstration of acoustical scale modeling

Acoustical scale modeling is possible because all the acoustical phenomena observed in the environment can be duplicated in scale. These can be clearly demonstrated using an impulsive sound source and an energy analyser. Absorption—The sound level reflected from a porous surface can be compared with the incident level to determine the noise reduction coefficient. Scattering—Multiple surfaces such as those forming the fenestrations of buildings, distribute sound but do not absorb it. The levels of specular and nonspecular reflections can be compared. Diffraction—For barriers, the relationship between noise reduction and Fresnel number can be seen. Factors that reduce the barriers effectiveness can be readily investigated. Reflection—The buildup of acoustical images can be observed as walls are added to form an interior space. Flutter, focussing and other characteristics can be observed. Ground effect—Sound traveling at grazing incidence across grassland can show a level reduction of up to 15 dB in mid- and low-frequency bands. In specific situations, obstacles reducing grazing may increase sound levels.