Hearing Loss Prevention (Noise)

Chapter 296-817, WAC

Effective Date: 08/01/03

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Noise Measurement and Computation

WAC 296-817-300 

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WAC 296-817-300

Your responsibility:

Conduct noise monitoring or measurement to evaluate employee exposures in your workplace

You must

Make sure that noise-measuring equipment meets recognized standards

Measure employee noise exposure
Use these equations when estimating full-day noise exposure from sound level measurements

 

Rules

WAC 296-817-30005

Make sure that noise-measuring equipment meets recognized standards

You must

  • Make sure that noise dosimetry equipment meets these specifications:
    • – Dosimeters must be equipment class 2AS-90/80-5 of the American National Rule Specification for Personal Noise Dosimeters, ANSI S1.25-1991, such dosimeters are normally marked "Type 2."

    Note

    Note:

    Make sure any dosimeter you use is Type 2 equipment that:

    • - Uses slow integration and A-weighting of sound levels.
    • - Has the criterion level set to 90 dB, so the dosimeter will report a constant 8-hour exposure at 90 dBA as a 100% dose.
    • - Has the threshold level set at 80 dB, so the dosimeter will register all noise above 80 dB.
    • - Uses a 5 dB exchange rate for averaging of noise levels over the sample period.

You must

  • Make sure that sound level meters meet these specifications:
    • – American National Standard Specification for Sound Level Meters, S1.4-1984, Type 2 requirements for sound level meters, such sound level meters are normally marked "Type 2."
        • For continuous noise measurements, the meter must be capable of measuring A-weighted sound levels with slow response
        • For impulse or impact noise measurements, the meter must be capable of indicating maximum C-weighted sound level measurements with fast response.
  • Calibrate dosimeters and sound level meters used to monitor employee noise exposure:
    • - Before and after each day's use
      AND
    • - Following the instrument manufacturer's calibration instructions.

Note

Note:

  • - You may conduct dosimetry using an exchange rate less than 5 dB and compare the results directly to the noise evaluation criteria in Table 1
  • - For measuring impulse and impact noise you may also use a sound level meter set to measure maximum impulse C-weighted sound levels or peak C-weighted sound levels.

WAC 296-817-30010

Measure employee noise exposure

IMPORTANT:

A noise dosimeter is the basis for determining total daily noise exposure for employees. However, where you have constant noise levels, you may estimate employee noise exposure using measurements from a sound level meter. Calculation of the employee noise exposure must be consistent with WAC 296-817-30015.

You must

  • Include all:
      • – Workplace noise from equipment and machinery in use
      • – Other noise from sources necessary to perform the work
      • – Noise outside the control of the exposed employees.
  • Use a noise dosimeter when necessary to measure employee noise dose
  • Use a sound level meter to evaluate continuous and impulse noise levels
  • Identify all employees whose exposures equal or exceed the Noise Evaluation Criteria as follows:
Noise Evaluation Criteria
Criteria
Description
Requirements
85 dBA TWA8 Full-day employee noise exposure dose. If you have one or more employees whose exposure equals or exceeds this level, you must have a hearing loss prevention program – Hearing protection
– Training
– Audiometric testing
90 dBA TWA8 Full-day employee noise exposure dose. If you have one or more employees whose exposure equals or exceeds this level, you must reduce employee noise exposures in the workplace – Noise controls
(in addition to the requirements for 85 dBA TWA8)
115 dBA measured using slow response Extreme noise level (greater than one second in duration) – Hearing protection
– Signs posted in work areas warning of exposure
140 dBC measured using fast response Extreme impulse or impact noise (less than one second in duration) Hearing protection

WAC 296-817-30015

Use these equations when estimating full-day noise exposure from sound level measurements

You must

  • Compute employee's full-day noise exposure by using the appropriate equations from Table 3 "Noise Dose Computation" when using a sound level meter to estimate noise dose.

Table 3
Noise Dose Computation
Description Equation
Compute the noise dose based on
several time periods of constant noise during the shift.
The total noise dose over the work day, as a percentage, is given by the following equation where Cn indicates the total time of exposure at a specific noise level, and Tn indicates the reference duration for that level.

The reference duration is equal to the time of exposure to continuous noise at a specific sound level that will result in a 100% dose. The reference duration, T, for sound level, L, is given in hours by the equation:

Given a noise dose as a percentage, compute the equivalent 8-hour time weighted average noise level The equivalent 8-hour time weighted average, TWA8, is computed from the dose, D, by the equation:

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