period four
Equipment Sound Rating
notes
Free Field
source
Figure 53
Fields of Measurement
To measure sound pressure correctly, it is important to understand the behavior of sound in various environments, or fields.
In theory, a free field is a homogeneous, isotropic medium that is free from boundaries. In practice, an example of a free field over a reflecting plane would be a large open area void of obstructions, like a parking lot or meadow.
An ideal sound source, that is, one that radiates sound equally in all directions, placed in a free field generates
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