Basic Documentation

Chapter 2–Physics of Sound
This experiment also shows another important element of sound wave transmission; that
sound waves traveling through air are not dependent upon movement of the air itself.
Although the air in the bell jar could not leave the jar, the sound traveled outward from the jar
without involving any physical movement of the air out from the inside of the bell jar.
Likewise, sound movement in a ventilation system is not dependent upon the movement or
direction of the airflow. Not only will sound generated in the supply side of a ventilation
system travel in the direction that the air happens to be moving to the areas served, but also
sound generated in an exhaust system will travel opposite the direction of airflow and also be
heard in the areas served by the exhaust system.
Sound Wave Parameters
Any analysis or study of sound (acoustics) is especially concerned with the generation and
reception of sound waves. It is necessary to first understand the fundamental concepts of
sound wave generation and how this relates to the overall science of acoustics. Once these
fundamentals are understood, actual quantifiers or measurement parameters can be applied
and used in actual acoustical design practice.
Figure 1 shows a diagram of the major parameters that apply to the analysis of sound. At the
left side of the diagram is the sound source shown as a solid dot. Anytime sound is produced,
there must be a sound source. When we speak, our vocal chords create sound and are the
sound source. As a sound source creates sound in the air, it radiates energy outward in the
form of compressed air waves or sound waves.
Figure 1. Sound Wave Parameters.
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