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Excessive noise levels in laboratory work spaces produced by the heating, ventilating, and air conditioning systems.

Tubbs RL
Appl Occup Environ Hyg 2001 May; 16:(5):497-501
Based on the observations and noise measurements of this health hazard evaluation, a noise problem existed at the complex. The noise levels exceed the ANSI evaluation criteria for determining the appropriate activities for laboratory and office space designs. Because most of the RC curves in the laboratories and offices have a hiss component in the sound spectrum, the air-balancing upstream in dampers should be moved the supply ducts at least three equivalent duct lengths back from the supply diffusers. This could be accomplished by moving the dampers and relocating them in the existing rectangular ducts. However, it may be advantageous to change the manner in which the supply air is delivered by copying the flexible duct design used in the administration building. This would eliminate the dampers being too close to the diffusers, and the short, 90+/- bends that create air turbulence that results in noise production. The flexible duct would have a slightly greater resistance to air flow which may allow the dampers to be opened a little more, further reducing the high frequency noise. Finally, a review of material from the manufacturer of the supply diffuser did not find any specifications on the noise characteristics of their product. Perhaps a diffuser with better noise attenuation could be located and installed during these changes. Once the changes have been completed, the HVAC system will need to be rebalanced. The oil-canning effect can be addressed when the system is being balanced by reinforcing the existing duct or replacing it with a stiffer duct material. Initial recommendations from an earlier survey to install isolation devices on the AHUs and pumps should be delayed until the high frequency noise is reduced. These isolators may, however, be necessary once the RC values are reduced by the above changes in the ducts, and the RC curve lowered. The lower frequency noises could be more prominent in the rooms' sound spectra to the point where these additional isolation changes will be necessary.
Noise; Ventilation-systems; Ventilation-equipment; Noise-exposure; Noise-control; Noise-levels
Dr. Tubbs, NIOSH, Hazard Evaluations and Technical Assistance Branch, 4676 Columbia Parkway, MS R-11, Cincinnati, OH 45226
Publication Date
Document Type
Journal Article
Tharr D
Fiscal Year
Issue of Publication
NIOSH Division
Source Name
Applied Occupational and Environmental Hygiene
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division