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2.2 FACTORS AFFECTING PROPAGATION OF SOUND There are several important factors, which affect the propagation of sound: geometric spreading, atmospheric effects, and surface effects. These are discussed separately below. 2.2.1 Geometric Spreading This refers to the spreading of sound energy as a result of the expansion of the wave fronts.
From the pinna to the tympanic membrane, sound is increased by 5 to 15 decibels (dB) in the 2,000 to 4,000 Hertz (Hz) range due to the resonance of the auditory canal. The human ear is most sensitive to sound within this range and most vulnerable to damage from noises that are too loud.