This might involve providing training on using sound level meters to perform surveys in work areas to identify areas with high noise levels. Hearing protection devices HPDs are considered the last option for controlling noise exposures. HPDs are generally used during the time it takes to implement engineering or administrative controls, or when such controls are not feasible.
Unless great care is taken in establishing a hearing conservation program, workers will often receive very little benefit from HPDs. The best hearing protector, when fitted correctly, is one that is accepted by the worker and worn properly. If the worker exposure is above 85 dBA 8-hour TWA , hearing protection must be made available, along with the other requirements in the hearing protection program.
Earplugs are designed to occlude the ear canal when worn. All hearing protectors are provided with an NRR. Although earplugs can offer protection against the harmful effects of impulse noise, and some earplugs are designed specifically to reduce this type of noise, the NRR is based on the attenuation of continuous noise and may not be an accurate indicator of the protection attainable against impulse noise.
Earmuffs are another type of hearing protector Figure They come in a variety of sizes, shapes, and materials and are relatively easy to dispense, as they are one-size devices designed to fit nearly all adult users. Earmuffs are designed to cover the external ear and thus reduce the amount of sound reaching the inner ear. Care must be taken to ensure that the seal of the earmuff is not broken by safety glasses, facial hair, respirators, or other equipment, as even a very small leak in the seal can destroy the effectiveness of the earmuff. Earmuffs should be chosen based on the frequency that needs to be reduced.
Refer to the EPA label on the manufacturer's product. Earmuffs are a good choice for intermittent exposure, given how easy they are to put on and take off. Hearing bands are a third type of HPD Figure 11 and are similar to earplugs, but with a stiff band that connects the portions that insert into a worker's ears. The band typically wraps around the back of the wearer's neck, though variations are available.
Hearing bands come in a variety of sizes, shapes, and materials and are popular for their convenience. Hearing bands may not provide the same noise attenuation as properly fitting earplugs, as the portions that fit into the ears are stationary and cannot be twisted into place like earplugs. Earplugs, earmuffs, or hearing bands alone might not provide sufficient protection from significantly high noise levels.
In this case, workers should wear double hearing protection-earmuffs with earplugs. Avoid corded earplugs, as the cord would interfere with the muff seal. Additionally, hearing bands cannot be worn with earplugs or earmuffs, as the connected band would interfere with the muff seal, and there is no room to insert earplugs at the same time. HPDs are rated to indicate the extent to which they reduce worker noise exposure. New technologies are being developed to test the effectiveness of earplugs and could eventually change the way hearing protection is rated.
Several sound-measuring instruments are available to CSHOs. These include sound level meters, noise dosimeters, and octave band analyzers. This section describes general equipment care, followed by the uses and limitations of each kind of instrument.
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Instruments that measure noise contain delicate electronics and require practical care. Store and transport the equipment in its custom case.
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Be aware of the instrument manufacturer's recommendations for proper storage for example, some manufacturers recommend removing all batteries from stored equipment, while others require a primary battery to remain in the instrument. Make sure batteries will last the anticipated sampling period. A battery tester can be useful. CSHOs may need to install fresh batteries or recharge reusable batteries with a battery charger.
Both pre- and post-inspection calibrations are required for any noise instruments used by CSHOs. It is important to understand the difference between these two types of calibrations. Calibrators must also be calibrated on an annual basis. Equipment manufacturers typically recommend periodic calibration on an annual basis.
These rigorous testing protocols ensure that the electronic components are in good working order and detect shifts in performance that indicate gradual deterioration. Periodic calibration results in a calibration certificate documenting the standard of performance. Typically, the instrument will also receive a sticker indicating its last calibration date and when the next periodic calibration is due Figure Do not continue to use it past the calibration date.
CTC also coordinates periodic factory calibration of any OSHA-owned noise-monitoring instruments that it does not service directly. Employers that lease or own Type I or Type II noise-measuring instruments can arrange annual calibration of the equipment through the equipment supplier or manufacturer.
During periodic calibration, the CTC also performs preventive maintenance to ensure that the equipment remains fully functional over its life expectancy. If the calibration team detects a problem, it services the instrument as necessary. When returning equipment to CTC for periodic calibration, be sure to include a note about any problems or concerns with equipment function so they can be evaluated as part of the maintenance process.
If equipment is not functioning well, CTC requests that the instrument be returned for inspection, even if it is not yet due for calibration. Octave band analyzers that are integrated into a sound level meter will be calibrated as part of the sound level meter.
However, detachable octave band analyzers must be returned to CTC for periodic calibration with the meter with which they are intended to be used. Pre- and post-calibration procedures confirm that the instrument is functioning properly on the day that it is used and prove that it is still registering sound levels correctly at the end of the day.
Pre- and post-calibrations also confirm that changes in temperature or humidity have not affected the instrument's accuracy. If practical, spot check the instrument with a calibrator after the stabilization period. Each instrument model is calibrated in a slightly different manner, but the general process follows basic standard steps. Typical daily pre-use calibration involves 1 setting up the instrument for use, 2 turning on both the electronic "calibrator" and the noise-measuring instruments to allow them to "warm up," 3 checking the calibrator and instrument battery charge, 4 testing the instruments with a standard tone of known pitch and intensity produced by the calibrator e.
For the post-use calibration check, the process is repeated, without step 5, after the instrument has been used. Both the pre- and post-use calibration must be documented If it isn't properly documented, it didn't happen. See Figures 13 and 14 for illustrations of this process for dosimeters and sound level meters, respectively. Confirm that you understand the procedures for calibrating each of the instruments you use. If in doubt, review instructions in each instrument's user's manual and consult CTC if questions arise.
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In general, as long as the sound level readout is within 0. If large fluctuations greater than 1 dB in the level occur, then either the calibrator or the instrument may have a problem. Additionally, confirm that you know how to change the battery in both the calibrator and the instruments. If in doubt, review instructions in each instrument's user's manual. A low battery is the number-one cause of equipment failing pre- and post-use calibration.
Changing the battery will often bring the equipment back into an acceptable calibration range immediately, but a little practice is needed to change the battery quickly on some equipment.
Be prepared, so that a low battery doesn't slow you down during an early morning calibration session Figure Noise measurements collected by CSHOs cannot be used as a basis for citations unless they are obtained using equipment that has a current within the past 12 months periodic calibration certificate on file and that has received documented calibration before and after the measurements were made using accepted practices for documentation, as outlined in the OSHA Field Operations Manual. Sound level meters provide instantaneous noise measurements for screening purposes Figure During an initial walkaround, a sound level meter helps identify areas with elevated noise levels where full-shift noise dosimetry should be performed.
Sound level meters are useful for:. The most widely used sound level meter for workplace evaluations, the Type 2 meter , performs with the minimum level of precision required by OSHA for noise measurements. These meters are usually sufficient for general purpose noise surveys. Likewise, the sound level meter can be expected to operate effectively between 10 and 90 relative humidity. The Type 1 meter accuracy, precision, and additional features make it the preferred model for obtaining readings that will be used to help design cost-effective noise controls.
For unusual measurement situations, refer to the manufacturer's instructions and appropriate ANSI standards for guidance in interpreting instrument accuracy. These meters, which are often modestly priced, can be useful pre-screening tools for employers seeking to identify noisy locations and track improvements during noise reduction efforts.
They cannot, however, be used to document compliance with OSHA standards; only properly calibrated Type 2 or Type 1 meters can serve that purpose. For example, sound level meter applications are available for some smartphones. Such an application can give a rough estimate of the noise level in a particular location but may not be used to document compliance with OSHA standards. All sound level meters are affected by temperature and humidity; however, these instruments are intended to provide reliable readings within the normal range of workplace temperatures. During extreme weather, temperatures might be considerably outside that range in untempered storage e.
Avoid carrying cold equipment into a very humid environment, which could permit moisture to condense on the instrument. To prevent this situation, do not keep noise equipment in the trunk of a cold car; instead, carry it in the passenger compartment and store it indoors at the destination. Sound level meters should be calibrated using the steps outlined in Section 1, above, and according to the manufacturer's instructions. Different work environments and different sound level meter microphones might require variations in measurement procedures.
For practical purposes, however, certain basic steps apply in most circumstances. Confirm that the sound level meter is properly calibrated and temperature-stabilized. Then, position the microphone in the monitored worker's hearing zone.
OSHA defines the hearing zone as a 2-foot-wide sphere surrounding the head. Considerations of practicality and safety will dictate the actual microphone placement at each survey location. Note that when noise levels at a worker's two ears are different, the higher level must be sampled for compliance determinations.