Almost all acoustical situations can be described by three parts: source, path, and receiver. Sometimes the source (human speech, HVAC equipment) can be made louder or quieter. For example, strategic placement of reflecting surfaces near the speaker in lecture rooms, churches, and auditoriums can reinforce and evenly distribute sound to all listeners. The path (air, earth, building materials) can be made to transmit more or less sound. When required, double-wall and other complex constructions can be designed to interrupt the sound path, thereby providing satisfactory sound isolation and privacy. The receiver (usually humans, although sometimes animals or sensitive medical equipment) also can be affected. Usually building occupants will hear better, or be more comfortable, if distracting HVAC system noise can be controlled or if intruding environmental noise can be isolated or removed. In most situations, it is best to focus on all three parts. For example, concentrating only on the direct path for sound travel through common walls may at best result in costly overdesign or at worst, no solution at all!

Acoustical requirements always should be considered during the earliest stages of design. Even though corrections can be accomplished during the mid-and latter stages of design, it usually is very difficult to change shapes, room heights, and adjacencies within buildings when spatial relationships and budgets have been fixed. Similarly, deficiencies in completed spaces are often extremely difficult and costly to correct. For example, the addition of an electronic, sound-reinforcing system to an auditorium which is excessively...