Occupational Noise Monitoring Guidelines

Noise can cause permanent and disabling hearing damage. Often, the hearing loss may not become apparent until several years later. Furthermore, long-term exposure to noise in the workplace is associated with hypertension and other chronic conditions. Therefore, effective noise monitoring is essential for preventing occupational hearing loss and ensuring compliance with safety and health standards.

This article provides comprehensive guidelines for occupational noise monitoring, covering standards from OSHA (Occupational Safety and Health Administration) and NIOSH (National Institute for Occupational Safety and Health), measurement methods, hearing protection, and elements of an effective hearing conservation program.

How to Measure Noise Exposure in the Workplace

Understanding Noise Measurement

Noise is measured in decibels (dB), using a logarithmic scale. With NIOSH standards, every three-decibel increase equates to double the amount of sound energy. This doubling of noise energy also equates to a doubling of the risk of hearing damage, making relatively small increases in decibels have a significant effect on employee health.

Key Noise Measurement Terminology:

Decibel (dB): A unit used to measure the intensity of a sound.
A-weighted decibels (dBA): Used to predict hearing risk.
Time-Weighted Average (TWA): The average noise level during a shift, typically 8 hours.

A-weighted noise levels (dBA) are commonly measured in dBA. Exposure limits are commonly measured in dBA.

Permissible Exposure Level (PEL): The OSHA noise exposure standards define two action levels at which worker protection must be provided and used. 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.

At no time shall any excursion exceed 115 dBA(Measured with the slow setting on a sound level meter or 140 dBC(Measured with the fast setting on a sound level meter.

Equivalent sound level contours. Octave band sound pressure levels may be converted to the equivalent A-weighted sound level by plotting them on this graph and noting the A-weighted sound level corresponding to the point of highest penetration into the sound level contours.

Regulatory Framework: OSHA and NIOSH Standards

The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) provide guidelines and regulations for noise exposure in the workplace. Understanding these standards is crucial for ensuring worker safety and regulatory compliance.

OSHA Standards:

According to OSHA 1910.95(d)(1), employers must develop and implement a noise monitoring program whenever information suggests that any employee’s exposure may equal or exceed an 8-hour time-weighted average (TWA) of 85 decibels (dBA). OSHA mandates noise monitoring when employee exposure may approach or exceed the action level of 85 dBA TWA. This requirement ensures that all employees who are at risk are identified and included in the Hearing Conservation Program.

NIOSH Recommendations:

NIOSH recommends an exposure limit of 85 dBA as an 8-hr TWA with a 3-dB exchange rate. For each 3 dBA increase in noise level, NIOSH recommends reducing the exposure duration by half. This is called the exchange rate. Similarly, if the daily exposure is longer than 8 hours, the allowable noise level is lower. NIOSH recommends annual audiometric testing for workers exposed to noise above the REL.

Key Regulatory Requirements:

Action Level: 85 dBA TWA
Permissible Exposure Limit (PEL): 90 dBA TWA
Exchange Rate: 3 dB (NIOSH), 5 dB (OSHA)

When employees are subjected to sound levels exceeding 85 dBA TWA, feasible administrative or engineering controls are to be utilized. If feasible engineering or administrative controls cannot be accomplished, personal hearing protective devices must be provided and used to reduce sound levels in areas above 85 dBA.

Signs are to be posted in areas where noise levels are above 85 dBA stating that hearing protection is required.

When is Noise Monitoring Required?

OSHA mandates noise monitoring when employee exposure may approach or exceed the action level of 85 dBA TWA. This requirement ensures that all employees who are at risk are identified and included in the Hearing Conservation Program.

Initial Monitoring: Employers must conduct initial noise monitoring to determine whether employees’ noise exposures are at or above the action level (OSHA 1910.95(d)(1)). This initial assessment helps identify which employees need to be included in the HCP and what level of hearing protection is required.

Ongoing Monitoring: Noise monitoring must be repeated whenever there are changes in production, processes, equipment, or controls that might increase noise exposures (OSHA 1910.95(d)(3)). This ensures that the program remains effective in protecting employees from new or intensified noise hazards.

Methods for Conducting Noise Monitoring

OSHA allows for two primary methods of noise monitoring: area monitoring and personal sampling. Both methods are used to assess noise levels and determine whether employees are at risk of exposure above the action level.

Area Monitoring: This method involves measuring noise levels in specific work areas to assess the overall environment. It is particularly useful in fixed workstations or areas where noise levels are relatively constant.

Personal Sampling: Personal sampling involves measuring the noise exposure at the employee's ear level, providing a more accurate assessment of individual exposure. This method is essential in environments with high worker mobility, significant variations in noise levels, or the presence of impulsive noise.

Tools for Noise Monitoring

Use personal noise dosimeters to best assess a worker's personal noise exposure. Measure workplace areas with a sound level meter (SLM) and create a noise map of facility areas. If an SLM is not available, sound measurement apps can provide a measure of area noise but may not comply with regulatory requirements.

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.

The world is getting louder. People cannot escape noise pollution in their everyday lives whether from traffic, infrastructure, music or more, but employees can and must be protected from excessive noise in the workplace. Employees that are subjected to loud, instantaneous noise can suffer from immediate noise induced hearing loss that cannot be repaired.

Attach the microphone to the top of the worker's shoulder on the side that is likely to have the highest exposure. If the device does not have a separate microphone this may not be necessary.

Key Instruments for Noise Measurement:

Sound Level Meter (SLM): Used to measure the intensity of sound at a specific point.
Noise Dosimeter: A personal device worn by employees to measure their cumulative noise exposure over a period of time.

Integration and Calibration of Noise Measurements

Accurate noise measurement is critical for effective noise monitoring. OSHA 1910.95(d)(2)(i) requires that all continuous, intermittent, and impulsive sound levels from 80 decibels to 130 decibels be integrated into the noise measurements. Additionally, instruments used for noise monitoring must be properly calibrated to ensure accuracy.

Instruments must be calibrated to ensure they provide accurate noise measurements. According to OSHA 1910.95(d)(2)(ii), this includes checking that the equipment is functioning correctly and that it is free from distortion or other errors that could affect measurement accuracy.

Responding to Noise Monitoring Results

Once noise monitoring is conducted, the results must be reviewed to determine whether additional protective measures are necessary. If noise levels exceed OSHA’s permissible exposure limits, employers must take steps to reduce exposure through engineering controls, administrative controls, or personal protective equipment (PPE).

According to OSHA 1910.95(e), employers must notify each employee exposed at or above the action level of 85 dBA TWA of the results of the noise monitoring. This ensures that employees are aware of their exposure levels and can take appropriate protective measures.

Employees or their representatives must be given the opportunity to observe any noise measurements conducted (OSHA 1910.95(f)). This transparency helps build trust and ensures that all stakeholders are informed about the risks and protective measures in place.

Following noise monitoring:

Calculate the TWA.
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.

Implementing a Hearing Conservation Program

All University employees whose noise exposures equal or exceeds an eight-hour time weighted average (TWA) of 85 decibels are enrolled in a hearing conservation program. 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.

Key elements of a hearing conservation program:

Exposure measurements.
Record retention.
Access to records.
Employee notification.
Observation of monitoring.

Hearing Protection

Hearing protection, like earplugs or earmuffs, can protect you from noise if worn correctly.

The hearing protection used will depend on the operation, employee preference and attenuation required. The safety and health officer is to assist in supplying information on attenuation data and supervise the correct use of hearing protectors. Employees are given the opportunity to select their hearing protectors from a variety of suitable hearing protectors.

The University strongly encourages the use of hearing protection devices while working around noisy equipment. For employees who have experienced a standard threshold shift, hearing protectors must attenuate employee exposure to an 8-hour time-weighted average of 85 decibels or below.

Audiometric Testing

Annual hearing tests help identify hearing loss in your employees. Annual audiometric testing is performed by a licensed or certified audiologist, at UNC School of Medicine’s Speech and Hearing department.

A baseline audiogram is obtained within 6 months of an employee’s first exposure at or above the action level. The baseline audiogram is established to compare against subsequent audiograms.

Audiometric tests are to be pure tone, air conduction, hearing threshold examinations, with test frequencies including as a minimum 500, 1000, 2000, 3000, 4000 and 6000 Hz.

Testing to establish a baseline audiogram shall be preceded by at least 14 hours without exposure to workplace noise.

Each employee's annual audiogram shall be compared to that employee's baseline audiogram to determine if the audiogram is valid and if a standard threshold shift as defined in paragraph (g)(10) of this section has occurred. The audiologist, otolaryngologist, or physician shall review problem audiograms and shall determine whether there is a need for further evaluation.

An audiogram is a graph of hearing thresholds at various frequencies in each ear. Thresholds which are 25 dB HL (hearing level) or better (lower) are considered normal for adults.

Annual audiometry. The evaluation at the programmatic level shall take place annually.

Employee Training

Employees need to be trained on noise and hearing protection. Employers shall make hearing protectors available to all employees exposed to an 8-hour time-weighted average of 85 decibels or greater at no cost to the employees.

The employer shall train each employee who is exposed to noise at or above an 8-hour time weighted average of 85 decibels in accordance with the requirements of this section. The training program shall be repeated annually for each employee included in the hearing conservation program.

An annual training program is provided for each employee included in the hearing conservation program.

You should tell workers they are having their noise exposure monitored and provide them with an explanation of the results. Involve workers in the noise monitoring process. They can provide important information about the work environment, machinery operation, and specific job tasks. Encourage workers to tell you when changes in equipment or production occur.