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TRG-TRC007-EN 5
period one
Fundamentals of Sound
notes
The wave form shown in Figure 5 represents sound occurring at a single
frequency. This is called a pure tone.
A pure sinusoidal wave form, however, is very rare in HVAC acoustics. Typically,
sounds are of a broadband nature, meaning that the sound is composed of
several frequencies and amplitudes, all generated at the same time. Figure 6
represents the components of broadband sound.
Alternatively, plotting the amplitude (vertical axis) of each sound wave at each
frequency (horizontal axis) results in a graphic of the broadband sound that
looks like this. As you can see from this example, the sound energy is greater at
some frequencies than at others.
Broadband Sound
amplitude
amplitude
time
time
Figure 6
Broadband Sound and Tones
amplitude
amplitude
frequency
frequency
tone
tone
logarithmic scale
logarithmic scale
Figure 7