By Mark E. Schaffer
A advisor that provides principles for controlling the noise and vibration of HVAC structures.
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Extra info for A Practical Guide to Noise and Vibration Control for HVAC Systems
Figure 2-2 compares the inlet LW values of three commercial 925 mm diameter fans operating at 9400 L/s and 750 Pa total pressure of similar motor kW rating, each of which has a different blade shape. The 125 hertz octave band “spikes” in the BI and AF spectra are due mainly to the strengths of their BPF tones. The FC fan’s LW spectrum does not show a strong BPF tone, but its higher 63 hertz band LW value can be a problem because of the expense required to control noise in that frequency band. Centrifugal fans of all types will produce unexpectedly high noise levels if duct fittings or other airflow obstructions are too close to the fan inlet or discharge.
Inlet side of a directdrive plenum fan. 34 © 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission. A Practical Guide to Noise and Vibration Control for HVAC Systems Figure 2-11 Power roof ventilators (mushroom fans) mounted on intake duct silencers and roof curbs. Since “add-on” noise control products, such as duct silencers or even ductwork, are often not feasible because of the static pressure losses that they create, selection of the quietest propeller fan available is often needed for a noise-sensitive application.
21 © 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission. General Design Guidelines Figure 1-19 Plan view of return air shaft with supply duct takeoffs obstructing return airflow. Construction Figure 1-20 generically compares the sound isolation performance of several shaft, chase, and enclosure constructions.
A Practical Guide to Noise and Vibration Control for HVAC Systems by Mark E. Schaffer