Physic Case - Sound Propagation

Introduction

Sound propagation is often being taken for granted, however it has several significant features that deserve our closer attention. In real life, sound waves can never travel forever in the same direction. It changes its direction for several reasons, which includes reflection, refraction and diffraction. In this paper, the focus would be on how reflection affects sound propagation. It would examine how reflection influences the construction of a concert hall and compare the quality with an outdoor venue such as amphitheatres and how outdoor acoustical problems can be handled.

Laws of reflection

When sound waves encounter an obstacle we expect them to be reflected. Sound waves will reflect from surfaces of any shape or size. If the surface is smooth, the reflection is regular and orderly (Figure 1a). On the other hand, a rough surface would cause irregular or diffuse reflection (Figure 1b). Regardless of the surface, the laws of reflection1 state that the angle of incidence is equal to the angle of reflection and that the incident ray, the normal, and the reflected ray are coplanar.

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Multiple reflection makes it possible for sound to travel from one room to another (Figure 2). This accounts for why you can often hear people talking in another room even though you cannot see them.

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