Evaluation of Low-Frequency Noise, Infrasound, and Health Symptoms at an Administrative Building and Men's Shelter: A Case Study

Abstract

Responses to complaints about low-frequency noise and infrasound at workplaces have not been extensively documented in the literature. The National Institute for Occupational Safety and Health evaluated low-frequency noise, infrasound, and health symptoms among employees of an organization providing services to homeless persons. The organization's campus was evacuated after two loud noise and vibration incidents related to methane flare on an adjacent landfill. Employees were interviewed about health symptoms, perceptions of noise, and how the incidents were handled. Available medical records were reviewed. Sound level and noise frequency measurements taken in vacated campus buildings not during these incidents revealed overall levels across frequencies up to 100 hertz were 64 to 73 dB, well below those associated with adverse health effects. However, an unbalanced frequency spectrum could have contributed to the unusual sounds or vibrations reported before the first incident. Some symptoms predating the incidents are consistent with low-frequency noise exposure but are also common and nonspecific. Most interviewed employees (57%) reported being uncomfortable returning to work on the campus. Multiple factors such as noise characteristics, health effects, and employee perceptions need to be considered when assessing health concerns related to low-frequency noise and infrasound.

Keywords: auditory symptoms; noise; octave band analysis; psychological contract; risk perception; vestibular symptoms.

Figure 1

Schematic of the campus and methane flares. Not drawn to scale. Employees worked in the administrative building or the men's shelter. Circles with A–D refer to parking lot locations where we made noise measurements. The closed landfill extends from the top edge of the fenced area to beyond the top of the diagram.

Figure 2

Photograph of the methane flares at the time of the site visit. (Photo by NIOSH.)

Figure 3

One-third octave band noise levels measured approximately 2.5 to 3 m (8–10 ft) from an operating methane flare and blower.

Figure 4

One-third octave band noise levels across eight rooms in the administrative building when a methane flare was on versus when the flare was off. The square or circle shows the median. The vertical line shows the range of noise levels.

Figure 5

Comparison of median one-third octave band noise levels measured in the administrative building with a flare on versus off to European indoor guidelines for low-frequency noise and infrasound. Maximum noise levels by frequency are shown as horizontal black bars. Guidelines were not established for all frequencies measured. German guidelines ( A ) covered 8–100 Hz. Polish guidelines ( B ) covered 10–250 Hz. Dutch guidelines ( C ) covered 20–100 Hz. British guidelines ( D ) covered 10–160 Hz. The square or circle shows the median. The vertical line shows the range of noise levels.

Figure 6

Number of employees reporting various symptoms related to unusual sounds or vibrations at work.