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OSHA Occupational Noise Regulations - 1910.95

The OSHA noise exposure standards define two action levels at which worker protection must be provided and used. These actions are based on the 8-hour Time Weighted Average (TWA) of the noise levels that the worker is exposed to throughout the working day:

TWA Dose Action Details
85 dBA + 50% + Hearing Conservation Program Provide hearing protection for workers to wear if they choose to.
Give training on the risks of high noise exposure.
Monitor the levels regularly in case they increase.
Provide audiometric testing.
90 dBA + 100% + Noise Control Program Provide hearing protection, which must be worn.
Provide training on the risks of high levels and the wearing of protection.
Provide audiometric testing.

The measurements for Hearing Conservation (HC) should be made using a noise dosimeter or sound level meter with its threshold set to 80dB. The measurements for Noise Control (NC) or permissible exposure level (PEL) should be made with a threshold of 90dB. Modern dosimeters such as the dBadge can measure both at the same time.

When noise levels are particularly high (say > 95 dBA) you should also check that the hearing protection that you are providing is adequate. A number of methods are available and the most accurate requires the use of a meter with Octave Band Filters.

noise calculators

Time Weighted Average - TWA - Noise Levels

These noise exposure limits are not based on instantaneous sound levels. They are based on the TWA (time weighted average) or Dose %, which indicates the average noise levels that the worker is exposed to throughout a working day.

The two most common ways to find out a workers TWA are:

osha sound level meter

1. Sound Level Meter - Manual Measurements

  • Measure the sound levels at the different times of day and different locations that the worker usually visits.
  • Find out how long the worker spends at each location.
  • Calculate the TWA. See TWA Calculator.

If a worker stays at just one or two locations with constant noise levels then this is a relatively easy task.

dosebadge noise dosimeter

2. Use a Noise Dosimeter

  • Fit the Noise Dosimeter to the worker at the start of the working day.
  • Remove the dosimeter at the end of the day and read off the TWA or Dose % figure.

The dosimeter approach is much easier when a worker moves between different locations or the noise levels are changing all the time.

When to Monitor the Noise Levels

The noise levels in a work place should be carefully monitored using the correct grade of equipment if there is any possibility that a worker will be exposed and an 8 hour time weighted average noise level of 85 dB(A) or above. This monitoring should be repeated periodically (e.g. every year or every two years) or whenever there is change to machinery, production levels or processes that may impact on the noise levels.

Which Sound Level Meter or Noise Dosimeter?

To be sure of getting accurate and repeatable noise measurements that can be used for protecting workers' hearing and protecting your company from legal claims, you should use the correct grade of sound level meter. The OSHA regulations recommend the use of a Type 2 sound level meter (you can also use Type 1 as it is more accurate) with "Slow" time weighting. You should also use a Sound Level Calibrator to check that the meter is operating correctly before making important measurements. Here are some suggestions:

sound level meter

CEL240 Type 2 Sound Level Meter
Ideal for quick measurements, from which you can calculate a worker's TWA.

Recommended: CEL240-K Noise Measurement Kit (includes the meter and a Calibrator) - $895.00

osha data logging sound level meter

CEL620 Integrating Sound Level Meter
Includes all the measurements for an occupational noise survey. Data logging included

Recommended: CEL260A2-K Sound Level Meter and Calibrator : $2033.00

real-time analyzer

CEL632 Advanced Integrating Sound Level Meter
More detailed data logging and removable preamplifier. Options for octave and 1/3 octave band filters.

Recommended: CEL632A2-K (includes meter and a Calibrator) - $2570.00

dosebadge noise dosimeter

dBadge Logging Noise Dosimeter
Mounts on the worker's shoulder and monitors the noise levels throughout the day.

Recommended: CEL350K5 Noise Dosimeter Kit (includes 5 dosimeters, Calibrator and accessories) -


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