Noise and Hearing Hazards | Facility Audit

Although noise-induced hearing loss is one of the most common occupational illnesses, it is often ignored because there are no visible effects, it usually develops over a long period of time, and, except in very rare cases, there is no pain. What does occur is a progressive loss of communication, socialization, and responsiveness to the environment. In its early stages (when hearing loss is above 2,000 Hertz (Hz)) it affects the ability to understand or discriminate speech. As it progresses to the lower frequencies, it begins to affect the ability to hear sounds in general.

The three main types of hearing loss are conductive, sensorineural, or a combination of the two.

The effects of noise can be simplified into three general categories:

• Primary effects, which includes noise-induced temporary threshold shift, noise-induced permanent threshold shift, acoustic trauma, and tinnitus.
  
  
• Effects on communication and performance, which may include isolation, annoyance, difficulty concentrating, absenteeism, and accidents.
  
  
• Other effects, which may include stress, muscle tension, ulcers, increased blood pressure, and hypertension.
  
  

Indications of a Problem

There are various factors that may indicate noise is a problem in the workplace. While people react differently to noise, subjective responses should not be ignored because they may provide warnings that noise may be at unacceptable levels.

• Noisy conditions can make normal conversation difficult.
  
  
• When noise levels are above 80 decibels (dB), people have to speak very loudly.
  
  
• When noise levels are between 85 and 90 dB, people have to shout.
  
  
• When noise levels are greater than 95 dB, people have to move close together to hear each other at all.

A walkaround survey should be performed to screen for noise exposures and to determine if additional monitoring is necessary. When screening for noise exposures, sound level meter measurements and estimates of the duration of exposure are sufficient. The resulting spot readings can be used to determine the need for a more complete evaluation.

The following general approach may be followed:

• Tour the facility and develop a detailed understanding of facility operations and potential noise sources. Take the tour with someone who is familiar with plant operations. Speak with knowledgeable personnel about operations and maintenance requirements. Make notes on a diagram of the floor plan if possible. Look for indications that noise may be a problem.
  
  
• Use a sound level meter to take spot readings of operations that are in question. It may be useful to mark the sound levels on a diagram of the floor plan. Make notes regarding what equipment is on or off.
  
  
• Estimate exposures by identifying workers and their locations and estimate the length of time they spend in different areas or how long they operate particular equipment or tools.
  
  
• If the results of the walkaround survey indicate time-weighted average (TWA) exposures of 80 dBA or more, then additional noise monitoring should be performed. Remember to take into account the accuracy of the sound level meter when making this estimation. For example, a Type 2 sound level meter has an accuracy of ±2 dBA.