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INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07) — PAGE 31
ENVIRONMENTAL CONSIDERATIONS — dB(A)
Reducing Noise
Structure-Borne Noise
Structure-borne noise is transmitted or generated as
vibrations in structures. Vibrating structures create sound
pressure waves (noise) in the surrounding air. Connections
to a genset can cause vibrations in the building structure,
creating noise. Typically, these include the skid anchors,
radiator discharge air duct, exhaust piping, coolant piping,
fuel lines, and wiring conduit. Also, the walls of a genset
housing can vibrate and cause noise.
The following will help reduce structure-borne noise:
1. Mounting a genset on spring-type vibration isolators
effectively reduces vibration transmission. See the
Mounting section of this manual for details (page 33).
2. Flexible connections to exhaust pipe, fuel line, air duct,
coolant pipe (remote radiator or heat exchanger
systems), and wiring conduit effectively reduce vibration
transmission. Flexible connections are required when
the genset is mounted on vibration isolators.
3. See Figure 5 on page 32 for typical measures in reducing
noise.
Reducing Noise
Airborne Noise
Airborne noise is usually the most dominant type of noise.
Airborne noise has a directional characteristic, particularly
at the high end of the frequency range. Table 9 below shows
ways of minimizing airborne noise.
The following will help reduce airborne noise:
1. Redirect noise away from receivers. Vertical radiator or
exhaust outlets point the noise away from people at
grade level and keep them out of the path of noise.
2. Line-of-sight barriers are effective in reducing noise. A
sound barrier wall will reduce noise by blocking the sound
path of travel. Making noise travel through a 90 degree
bend in a duct reduces high frequency noise.
3. Cover enclosure walls, ceiling, and air duct with sound
absorbing (acoustic) material.
4. Remote radiators with low speed fans can be used both
to reduce the level of noise at the source and to isolate
it.
5. Critical grade mufflers are recommended whenever noise
control is a concern. The objectionable portion of engine
exhaust noise falls within the range of 125 to 1,000 hertz.
Regardless of the grade of muffler selected, its effective
(peak) attenuation should be within this frequency range.
Typical noise attenuating ratings of mufflers are as
follows:
sgnitaRrelffuMdetaunettAesioN.9elbaT
relffuMlairtsudnI)A(Bd81-21
relffuMlaitnediseR)A(Bd52-81
relffuMlacitirC)A(Bd53-52