TABLE OF CONTENTS Practical acoustic problems are invariably associated with people, buildings, rooms, airplanes, automobiles, etc. These can generally be classified either as problems in physics (sound as a stimulus) or problems in psychophysics (sound as a perception), and often as both. Acoustical problems can be very complex in a physical sense, for example, thousands of reflected components might be involved or obscure temperature gradients might bend the sound in such a way as to affect the results. When acoustical problems involve human beings and their reactions, complexity takes on a whole new meaning.
Don t be discouraged if you want a practical understanding of acoustics, but your background is in another field, or you have little technical background at all. The inherent complexity of acoustics is pointed out only to justify going back to the inherent simplicity of sound in a free field as a starting point in the study of other types of practical sound fields.
Sound in a free field travels in straight lines, unimpeded and undeflected. Unimpeded sound is sound that is unreflected, unabsorbed, undiffracted, unrefracted, undiffused, and not subjected to resonance effects. These are all hazards that could (and do) face a simple ray of sound leaving a source.
Free space must not be confused with cosmological space. Sound cannot travel in a vacuum; it requires a medium such as air. Here, free space means any air space in which sound acts as though it is in the theoretical free space. Limited free...
