Page 241 - Master Handbook of Acoustics

FIGURE 12-1 A sound ray impinging on an acoustical material on a masonry wall undergoes
reflection from three different surfaces and absorption in the air and two different materials, with
different degrees of refraction at each interface. In this chapter, the cumulative absorbed component
is of chief interest.

More interestingly, some of the sound penetrates the acoustical material represented by the shaded

layer in Fig. 12-1. In this illustration, the direction of travel of the sound is refracted downward
because the acoustical material is denser than air. There is heat lost F by the frictional resistance the
acoustical material offers to the vibration of air particles. As the sound ray strikes the surface of the
concrete blocks, two things happen: a component B is reflected, and the ray is also bent strongly