Table of Contents

8.1 Introduction

8.2 Noise Exposure Limits and Hearing Conservation Program

8.3 Procedure

8.4 Training

8.5 Engineering Controls

8.6 Noise Reduction Ratings

8.1 Introduction #

High noise levels have the potential to result in permanent hearing loss, and it is important to reduce personal exposures to the extent feasible. Employees shall be trained in the selection, use, and care of hearing protection and will be provided with adequate hearing protection for the high-noise environments in which they are expected to occupy. Employees will wear appropriate hearing protection for their work area. This program is intended to be more protective than the governing regulations in an effort to reduce University employee noise exposures and ultimately prevent hearing loss.

High noise exposure can present many different health concerns:

• Hearing loss – Hearing loss is but one of the health concerns associated with high noise exposure.  Hearing loss can be acute/temporary (symptoms from exposure present themselves quickly and are significant, but go away after a short time) or chronic/long term (symptoms develop gradually over a long period to the point where the individual may not be aware of the change). Damage to your hearing is permanent. Once lost, it will not come back.
• Tinnitus – Tinnitus can be caused by prolonged exposure to loud noise and results in a sensation of hearing sound (usually a ringing, buzzing, or hissing sound) when no external sound is present. Tinnitus can be difficult to treat and may never go away. Prevention is the best course of action.

Reference Regulation: Occupational Noise Exposure (MIOSHA General Industry Part 380)

8.2 Noise Exposure Limits and Hearing Conservation Program #

When employees are subjected to sound exceeding those listed in the table below, feasible administrative or engineering controls should be utilized. If such controls fail to reduce sound levels, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.

Table 1. National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limits

Employees will be enrolled in a hearing conservation program whenever employee noise exposures equal or exceed the Michigan Occupational Safety and Health Administration (MIOSHA) 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.

8.3 Procedure #

Supervisors will identify high noise level operations or work areas and follow the procedures below by contacting the EHS representative assigned to their department/unit, or call EHS at 647-1143 to request that EHS measure and evaluate the noise levels using a sound level meter and/or noise dosimeter. When completed, EHS will submit a summary report of the findings and recommendations to the department/unit.

Supervisors will implement EHS recommendations. The feasibility of controlling noise levels at the source will be considered as the first option prior to using personal protective equipment.

Employees whose exposures are greater than the MIOSHA 8 hour time weighted average of 85 dBA will be enrolled in the University Hearing Conservation Program. As part of this program:

• Employees will be informed when monitoring results are at or above the 85 dB Action Level.
• The EHS Medical Surveillance Coordinator (615-2140) will schedule baseline audiometric testing (at no cost) shortly after hire. This will be conducted according to the Medical Surveillance procedures for Audiometric Testing.
• Supervisors will assure employees correctly use hearing protection and are properly fitted as described in the EHS report. Employees shall be given the opportunity to select their hearing protectors from a variety of suitable hearing protectors provided by the employer, at no cost.
• Employees will take hearing conservation training annually.
• Supervisors will make copies of the MIOSHA Occupational Noise Exposure Standard available to affected employees or representatives and shall post a copy in the workplace.

Employees will be scheduled automatically for annual audiometric testing, after the initial baseline test. The results will be compared to the employee’s baseline test by the health care provider to determine if a Standard Threshold Shift (STS) has occurred. A physician shall review the audiogram and repeat the testing within 30 days to confirm the results if deemed necessary. When an STS is confirmed, the employee will be notified in writing within 21 days of the determination. 

The employee’s supervisor will be informed of the notification of an STS and if necessary, arrangements will be made for additional noise monitoring of job tasks in the department. Results of the noise monitoring will be discussed with the affected employees and supervisor. The written noise monitoring report will be retained in the EHS medical surveillance file, and copies will be sent to the employee, supervisor, and Work-Connections (if recordable injury).

Employees not already using hearing protectors shall be fitted with hearing protectors that attenuate the employee exposure at least to a time-weighted average of 85 decibels, trained in their use and care, and required to use them.  

Employees already using hearing protectors shall be refitted and retrained in the use of hearing protectors, and provided with hearing protectors offering greater attenuation, if necessary.

8.4 Training #

Hearing conservation training, for newly hired employees that are to be included in the Hearing Conservation Program, will be conducted as part of safety orientation training. Training for existing employees, or employees hired in the past, that are now included in the Hearing Conservation Program, will be done as part of regularly scheduled annual safety retraining.

All hearing conservation training will be documented as required in the safety training program.

• Effects of Noise on Hearing
• Purpose of Hearing Protectors
• Advantages and Disadvantages of Hearing Protectors
• Selection, Fitting, Use, and Care of Hearing Protectors
• Audiometric Testing

8.5 Engineering Controls #

Engineering controls are the preferred method of addressing high noise levels as they can reduce or even eliminate the need for PPE to reduce noise exposures. Some examples of potential engineering controls are:

• Isolating the noise source from workers in the area.
• Erecting a barrier between the source and areas where workers are likely to be present.
• Altering the machine (with manufacturer approval) to reduce noise output.

8.6 Noise Reduction Ratings #

Hearing protection devices will be rated with a Noise Reduction Rating (NRR). A NRR is a standardized measure, expressed in decibels (dB), that indicates how effectively a hearing protection device reduces noise levels when worn correctly. The higher the Noise Reduction Rating (NRR), the greater the potential noise reduction. When determining the necessary level of protection, the goal is to choose a noise reduction rating that will reduce the exposure to below 85dB. If it is not possible to achieve the necessary reduction, the length of the exposure may need to be limited to avoid an overexposure. 

Figure 1. Example of a Noise Reduction Rating Label

Noise Reduction Ratings are determined in controlled laboratory settings.  NRRs achieved in a laboratory will be nearly impossible to obtain in the real world.  Because of this, hearing protection should be derated for field use. OSHA recommends subtracting 7 decibels from the NRR and then applying  a reduction of 50% to get the real-world value [(NRR-7) x 50%]. 

For example, consider a worker who is exposed to 98 dBA for 8 hours and whose hearing protectors have an NRR of 25 dB. We can estimate the worker’s resultant exposure using the 50% safety factor. The worker’s resultant exposure is 89 dBA in this case. Estimated dBA exposure = 98 dBA – [(25-7) × 50%] = 89 dBA.

Dual hearing protection involves wearing two forms of hearing protection simultaneously (e.g. earplugs and earmuffs). The noise exposure for workers wearing dual protection may be estimated by the following method. Determine the hearing protector with the higher rated NRR (NRRh) and subtract 7 dB. Add 5 dB to this field-adjusted NRR to account for the use of the second hearing protector.

For example, if an employee’s 8-hour TWA=110 dBA and they utilize both a plug with a NRR=29 and a muff  with a NRR=25 dB, the estimated dBA exposure = 110 – [(29 – 7) + 5] = 83 dBA.

Try not to choose more protection than is necessary to reduce your exposure below the recommended level. Too much protection can make it difficult to hear the sounds you need to hear and create a dangerous situation or make it less likely that you will wear your hearing protection.