Chapter hvac engineering Fundamentals: Part 1 Introduction

20.3.3
Loudness and frequency
Sound may be visualized as traveling in a wave pattern similar to that
of alternating electric current (Fig. 20.2). Variation above and below
the reference is called the
amplitude
and determines the loudness. The
Engineering Fundamentals: Part 5
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Engineering Fundamentals: Part 5
487
TABLE
20.1 Sound Power Outputs
* With afterburner.
†
Four jet engines.
‡
Four propeller engines.
SOURCE
: Copyright 1987, American Society of Heating, Refrigerating and Air Conditioning
Engineers, Inc., www.ashrae.org. Reprinted by permission from ASHRAE Handbook,
1987
Systems and Applications; 2001 Fundamentals,
Chap. 7, Table 2, is similar.
Figure 20.2
Wavelength and amplitude of sound.
distance from one wave peak to the next is the
wavelength,
the recip-
rocal of which is the
frequency
or
pitch
of the sound. Frequency is
measured in cycles per second (cps). The term
hertz
(abbreviated Hz)
is used instead of cycles per second. Figure 20.2 represents a pure
tone—one single frequency. Most sound is made up of several fre-
quencies (tones), with each frequency having a different loudness. For
Engineering Fundamentals: Part 5
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Any use is subject to the Terms of Use as given at the website.

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