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TRG-TRC007-EN 51
period four
Equipment Sound Rating
notes
The near field is an area adjacent to the source where sound does not behave
as it would in a free field. Most sound sources, including all HVAC equipment,
do not radiate sound in perfectly spherical waves. This is due to the irregular
shape of the equipment and different magnitudes of sounds radiating from the
various surfaces of the equipment. These irregularities cause pressure-wave
interactions that make the behavior of the sound waves unpredictable.
Sound-pressure measurements should not, therefore, be made in the near field.
The size of the near field is dependent on the type of source and dimensions
of the equipment.
Near Field
near
field
near
near
field
field
source
source
Figure 56