McQuay AGZ 030AM, Руководство по эксплуатации продукта

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Product Manual AGZ-2 AGZ 030A through 065A 21
Sound Pressure Levels - Full Load
All sound pressure tables give the overall "A" weighted sound pressure levels which are considered
typical of what may be measured in a free field with a hand held sound meter, in the absence of any
nearby reflective surfaces. The sound pressure levels are measured at 30 feet (10 meters) from the side
of the unit at 100% unit load and ARI conditions. 95°F (35°C) ambient air temperature and 54/44°F
(12/7°C) evaporator water temperatures for air-cooled units.
Sound Power Levels
Acoustical consultants may require sound power octave band data to perform a detailed acoustical
analysis. The tables present sound power levels per ARI Standard 370, “Sound Rating of Large
Outdoor Refrigerating and Air Conditioning Equipment”. These standards were developed to establish
uniform methods of determining the sound power radiated by large outdoor and indoor equipment.
The aforementioned methods are based on providing sound power levels by octave band and the
overall ‘A’ weighted value. Measurements are taken over a prescribed area around the unit and the data
is mathematically calculated to give the sound power, dB.
Sound Reduction due to Distance from the Unit
The distance between a source of sound and the location of the sound measurement plays an important
role in minimizing sound problems. The equation below can be used to calculate the sound pressure
level at any distance if the sound power is known.
Sound pressure can be calculated at any distance from the unit if the sound power is known.
Lp=Lw-(20 log r) + (10 log Q) - .5
Lp = sound pressure
Lw = sound power
r = distance from unit in feet
Q = directionality factor
The directionality factor is a dimensionless number that compensates for the type of sound radiation
from the source. Figure 6 shows the typical Q values of different reflecting surfaces.
For a unit sitting on a flat roof with no other reflective surfaces or attenuation due to grass, snow, etc.,
between source and receiver: Q=2.
With Q=2, the equation simplifies to:
Lp = Lw - (20)(log r) + 2.5
Figure 6, "Q" Values
Uniform Spherical Radiation Uniform Hemispherical Radiation Uniform Radiation over 1/4 of sphere
Q=1 no reflecting surface Q=2 single reflecting surface Q=4 two reflecting surfaces