TABLE OF CONTENTS It is well known that sound travels around corners and aroundobstacles. Music reproduced in one room of a home can be heard down the hall and in other rooms. Diffraction is one of the mechanisms involved in this. The character of the music heard in distant parts of the house is different. In distant rooms the bass notes are more prominent because their longer wavelengths are readily diffracted around corners and obstacles.
Wavefronts of sound travel in straight lines. Sound rays, a concept applicable at mid/high audible frequencies, are considered to be pencils of sound that travel in straight lines perpendicular to the wavefront. Sound wavefronts and sound rays travel in straight lines, except when something gets in the way. Obstacles can cause sound to be changed in its direction from its original rectilinear path. The process by which this change of direction takes place is called diffraction.
Alexander Wood, the early Cambridge acoustician, recalled Newton's pondering over the relative merits of the corpuscular and wave theories of light. Newton finally decided that the corpuscular theory was the correct one because light is propagated rectilinearly. Later it was demonstrated that light is not always propagated rectilinearly, that diffraction can cause light to change its direction of travel. In fact, all types of wave motion, including sound, are subject to diffraction.
The shorter the wavelength (the higher the frequency), the less dominant is the phenomenon of diffraction. Diffraction is less noticeable for light than it is for...
