Occupational Safety & Health Administration

develops standards to protect employees and the public

from the effects of noise exposure. The following informal discussion is a summary of portions of the regulations and reference material related to measuring noise exposure and its effects. For formal discussions, one should reference OSHA’s  most recent and complete version of the 1910.95 regulations for accurate details and information that is up to date.

Appendix 1910.95 App G of the standards is titled

Monitoring noise levels non-mandatory informational appendix – 1910.95

the appendix provides information to help employers comply with the noise monitoring obligations. An informal summary of highlights and portions of the document are presented below, see the original document, Monitoring noise levels non-mandatory informational appendix, for formal details.

The purpose of noise monitoring

is 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. A hearing conservation program is needed if employees are exposed to average noise levels of 85 dB or greater during an 8 hour workday.

noise exposure compactor

Noise Exposure From a Vibrating Compactor

When exposures are at or above 85 dB  it is necessary to have a noise monitoring program.

Factors which 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, or noisy conditions which make normal conversation difficult. The employer should 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.

Noise is generally measured using two different types of  noise testing equipment,

A sound level meter is a device that measures

the intensity of sound at a given moment. Sound levels vary with time and location in a work environment. Thus, a sound meter is used to take measurements throughout a workday and at various locations to map possible areas of concern. “This measurement method is generally referred to as “area” noise monitoring.”

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.” A dosimeter monitors an employee’s noise exposure during his or her’s workday. “Since the dosimeter is worn by the employee, it measures noise levels in those locations in which the employee travels.” This type of monitoring is suited more towards persons who move through a facility and are exposed to various intensities of noise “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.”

Revise area maps and more closely monitor employees noise exposures

“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.”

Noise testing equipment can be rented, purchased, or provided by professionals

If equipment is needed on a periodic basis, renting sound level meters or dosimeters may be a better choice then buying equipment. Since there is a large variety of noise testing equipment available, renting often provides an employer a way to determine the level of sophistication needed to monitor the facility and its employees. Professionals, such as, industrial hygienists, acoustical engineers, and audiologists may be a good route for assistance in getting started or for long term monitoring. “Free, on-site assistance may be obtained from OSHA-supported state and private consultation organizations. These safety and health consultative entities generally give priority to the needs of small businesses.”

Occupational Health and Environmental Control Standard Number: 1910.95 Titled “Occupational noise exposure”

States that protection is required when sound levels exceed

the levels shown and discussed in Table G-16.


Duration per day, hours

Sound level dBA slow response











1 ½ or 1.5




½ or 0.5


Less than or equal to 0.25 hours or 15 minuets


Footnote(1) When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractions: C(1)/T(1) + C(2)/T(2) C(n)/T(n) exceeds unity, then, the mixed exposure should be considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, and Tn indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.

In other words F(e)=(T(1)divided by L(1))+(T(2)divided by L(2))+ … + (T(n) divided by L(n)) where:


F(e) = The equivalent noise exposure factor.

T    = The period of noise exposure at any essentially constant level.

L    = The duration of the permissible noise exposure at the constant level (from the above table).

If the value of F(e) exceeds unity (1) the exposure exceeds permissible levels.

If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous.

Measured levels are generally determined with a sound level meter and/or dosimeter.

Levels are measured on the A scale of a standard sound level meter at slow response or octave band sound pressure levels may be converted to the equivalent A-weighted sound level by plotting values on the graph below and noting the A-weighted sound level corresponding to the point of highest penetration into the sound level contours. This equivalent A-weighted sound level, which may differ from the actual A-weighted sound level of the noise, is used to determine exposure limits from Table 1.G-16.



Octave band sound pressure conversion to A-weighted sound level

Octave band sound pressure levels converted equivalent A-weighted sound level graph











OSHA States

“The employer shall administer a continuing, effective hearing conservation program, as described in paragraphs (c) through (o) of this section, whenever employee noise exposures equal or exceed an 8-hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale (slow response) or, equivalently, a dose of fifty percent. For purposes of the hearing conservation program, employee noise exposures shall be computed in accordance with appendix A and Table G-16a, and without regard to any attenuation provided by the use of personal protective equipment.”


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