FAQs about Hearing Conservation

What is the purpose of noise monitoring?

OSHA’s Occupational Noise Exposure Standard (29 CFR 1910.95) requires you to place employees in a hearing conservation program if they are exposed to average noise levels of 85 dB or greater during an 8-hour workday. In order to determine if exposures are at or above this level, it may be necessary to measure or monitor the actual noise levels in the workplace and to estimate the noise exposure or “dose” received by employees during the workday.

When is it necessary to implement a noise monitoring program?

It is not necessary for every employer to measure workplace noise. Noise monitoring or measuring must be conducted only when exposures are at or above 85 dB. Factors that suggest that noise exposures in the workplace may be at this level include:

• Employee complaints about the loudness of noise
• Indications that employees are losing their hearing
• Noisy conditions that make normal conversation difficult

Also consider any information available regarding noise emitted from specific machines. In addition, actual workplace noise measurements can suggest whether or not a monitoring program should be initiated.

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How is noise measured?

Basically, there are two different instruments to measure noise exposures.

A sound-level meter is a device that measures the intensity of sound at a given moment. Since sound-level meters provide a measure of sound intensity at only one point in time, it is generally necessary to take a number of measurements at different times during the day to estimate noise exposure over a workday. If noise levels fluctuate, the amount of time noise remains at each of the various measured levels must be determined.

To estimate employee noise exposures with a sound-level meter, it is also generally necessary to take several measurements at different locations within the workplace. After appropriate sound-level meter readings are obtained, people sometimes draw “maps” of the sound levels within different areas of the workplace. By using a sound-level map and information on employee locations throughout the day, estimates of individual exposure levels can be developed. This measurement method is generally referred to as “area” noise monitoring.

Area monitoring can be used to estimate noise exposure when the noise levels are relatively constant and employees are not mobile. In workplaces where employees move about or where the noise intensity tends to fluctuate over time, noise exposure is generally more accurately estimated by the personal monitoring approach.

A dosimeter is like a sound-level meter except that it stores sound-level measurements and integrates these measurements over time, providing an average noise exposure reading for a given period of time, such as an 8-hour workday. With a dosimeter, a microphone is attached to the employee’s clothing, and the exposure measurement is simply read at the end of the desired time period. A reader may be used to read out the dosimeter’s measurements.

Since the dosimeter is worn by the employee, it measures noise levels in those locations in which the employee travels. A sound-level meter can also be positioned within the immediate vicinity of the exposed worker to obtain an individual exposure estimate. Such procedures are generally referred to as “personal” noise monitoring.

In situations where personal monitoring is appropriate, proper positioning of the microphone is necessary to obtain accurate measurements. With a dosimeter, the microphone is generally located on the shoulder and remains in that position for the entire workday. With a sound-level meter, the microphone is stationed near the employee’s head, and the instrument is usually held by an individual who follows the employee as he or she moves about.

Manufacturer’s instructions, contained in dosimeter and sound-level meter operating manuals, should be followed for calibration and maintenance. To ensure accurate results, it is considered good professional practice to calibrate instruments before and after each use.

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How often is it necessary to monitor noise levels?

When there are significant changes in machinery or production processes that may result in increased noise levels, remonitoring must be conducted to determine whether additional employees need to be included in the hearing conservation program. Many companies choose to remonitor periodically (once every year or two) to ensure that all exposed employees are included in their hearing conservation programs.

Tomorrow, we’ll show you what it takes to have an award-winning hearing conservation program.

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