Geometrical acoustics

Geometrical acoustics or ray acoustics is the equivalent principle of geometrical optics applied in acoustics.^[1] Geometrical optics, or ray optics, describes light propagation in terms of rays. The ray in geometric acoustics is an abstraction, or instrument, which can be used to approximately model how sound will propagate. Sound rays are defined to propagate in a rectilinear path as far as they travel in a homogeneous medium. This is a simplification of sound that fails to account for sound effects such as diffraction and interference. It is an excellent approximation, however, when the wavelength is very small compared with the size of structures with which the sound interacts.

Practical applications

Practical applications of the methods of geometric acoustics are made in very different areas of acoustics. For example, in architectural acoustics the rectilinear properties of sound rays make it possible to determine reverberation time in a very simple way. The operation of fathometers and hydrolocators is based on measurements of the time it takes for sound rays to travel to a reflecting object and back. The ray concept is used in designing sound focusing systems. An approximate theory for sound propagation in nonhomogeneous media (such as the ocean and the atmosphere) has been developed on the basis of the laws of geometric acoustics.

The methods of geometric acoustics have a limited field of application because the ray concept itself is only valid for those cases where the amplitude and direction of a wave undergo little change over distances in the order of the length of a sound wave. Specifically, when using geometric acoustics it is necessary that the dimensions of the rooms or obstacles in the sound path should be many times greater than the wavelength. If the characteristic dimension for a given problem becomes comparable to the wavelength, then wave diffraction begins to play an important part, and this is not covered by geometric acoustics.^[1]

Software applications

The concept of geometrical acoustics is widely used in software applications. Some software applications that use geometrical acoustics for their calculations are ODEON, Enhanced Acoustic Simulator for Engineers, and Olive Tree Lab Terrain.

References

External links

• ODEON Room Acoustics Software
• EASE – Industry Standard for Acoustical Simulation of Rooms
• Olive Tree Lab Terrain