Hearing conservation program


Hearing conservation programs are programs that should reduce the risk of hearing loss due to hazardous noise exposure, if implemented correctly and with high quality. Hearing conservation programs require knowledge about risk factors such as noise and ototoxicity, hearing, hearing loss, protective measures to prevent hearing loss at home, in school, at work, in the military and, and at social/recreational events, and legislative requirements.
Regarding occupational exposures to noise, a hearing conservation program is required by the Occupational Safety and Health Administration "whenever employee noise exposures equal or exceed an 8-hour time-weighted average sound level of 85 decibels measured on the A scale or, equivalently, a dose of fifty percent." This 8-hour time-weighted average is known as an exposure action value. While the Mine Safety and Health Administration also requires a hearing conservation program, MSHA does not require a written hearing conservation program. MSHA's hearing conservation program requirement can be found in 30 CFR § 62.150, and is very similar to the OSHA hearing conservation program requirements. Therefore, only the OSHA standard 29 CFR 1910.95 will be discussed in detail.
According to Alice Sater, employers are not implementing these programs effectively, personal protective equipment does not protect workers well, and the risk of hearing loss is not reduced.

Program requirements

The OSHA standard contains a series of program requirements.
  • Engineering Controls: 29 CFR 1910.95 requires that "feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels...personal protective equipment shall be provided and used to reduce sound levels..."
  • Noise Monitoring: 29 CFR 1910.95 requires that monitoring be conducted when "any employee's exposure may equal or exceed an 8-hour time-weighted average of 85 decibels.
  • Audiometric Testing: 29 CFR 1910.95 requires an "audiometric testing program" for "all employees whose exposures equal or exceed an 8-hour time-weighted average of 85 decibels".
  • Hearing Protectors: 29 CFR 1910.95 states that "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"
  • Training: 29 CFR 1910.95 mandates an annual "training program" for "all employees who are exposed to noise at or above an 8-hour time-weighted average of 85 decibels..." and mandates certain aspects of the training that must be included. This includes the effects of noise on hearing; purpose, advantages, disadvantages, and attenuation of different types of hearing protectors; purpose audiometric testing.
  • Record Keeping: 29 CFR 1910.95 states that employers "shall maintain an accurate record of all employee exposure measurements..."

    Sound survey

A sound survey is often completed to determine areas of potential high noise exposure. A noise screening is completed initially to determine which areas are higher than 80 dB A. For these areas, an official sound survey will take place. This type of survey is normally completed using a sound level meter. A sound level meter takes a measurement of the sound present in the environment at that moment. There are three types of sound level meters. Type 0 is a precision instrument normally used in laboratories. Type 1 is for precision measurements taken in the field. Type 2 sound level meters are less precise than type 1 and are often used to take all-purpose sound level measurements. There are also noise dosimeters that are worn on the body and measure the amount of noise exposure an individual receives over a given time period. OSHA guidelines state that either a SLM or noise dosimeter may be used for sound monitoring.
Surveys must be repeated when there are significant changes in machinery and/or processes that would affect the noise level.

Engineering and administrative controls

and administrative controls are ranked as the most effective protection from noise in the hierarchy of controls. Engineering controls are measures taken to reduce the intensity of noise at the source or between the source and a person exposed to the noise. This can be done by choosing tools that make less noise, installing a barrier between the worker and the noise, enclosing the machinery all together, or making sure the machinery is maintained properly. Administrative controls are limitations around noise sources that limit length of noise exposure. Some known methods are running loud equipment when less workers are present, controlling the amount of time a worker is allowed around the noise source, constructing areas that allow employees a chance to escape from the noise, or increasing the distance between the worker and the excessive noise source.

Hearing protection devices

If engineering controls fail to maintain an 8-hour time-weighted average below 85 dBA, then a hearing protection device is required. There are two general types of HPDs: earplugs and earmuffs. Each one has its own benefits and drawbacks. The selection of the proper HPD to be worn is commonly done by an industrial hygienist so that the proper amount of noise protection is worn. OSHA requires that HPD be given free of charge.

Earplugs

There are four general classes of earplugs. These include: pre-molded, formable, custom molded and semi-insert.
  • Premolded earplugs do not require the plug to be formed before it is inserted into the ear. This prevents the plugs from becoming soiled before insertion.
  • Formable earplugs are made of a variety of substances; however, all each substance shares the common feature of being able to be shaped by the user prior to insertion. One drawback of this is the obvious need for the user to have clean hands while shaping the earplug. They do have the advantage of forming to the users ear, while many premolded earplugs do not accomplish this very well.
  • Custom molded ear plugs are unique for each person, since they are cast from each user's own ear canals. Therefore, they provide a personalized fit for each individual.
  • Semi-inserts are generally a soft earplug on the end of band. The band aides in maintaining the earplug in position. They are often useful since they can be quickly removed and inserted.

    Earmuffs

s are another type of HPD. The main difference between earmuffs and earplugs, is that earmuffs are not inserted inside the ear canal. Instead the muffs create a seal around the outside of the ear to prevent noise from reaching the inner ear. Earmuffs are easy to wear and often provide a more consistent fit than an earplug. There are earmuffs available that use the principle of active noise control to help reduce noise exposures. However, the protection earmuffs offer may be mitigated by large sideburns or glasses as the seal of the earmuffs may be broken by these objects.

Noise reduction ratings

The United States Environmental Protection Agency requires that all hearing protection devices be labeled with their associated noise reduction rating. The NRR provides the estimated attenuation of the hearing protection device. The NRR obtained in the lab is often higher than the attenuation provided in the field. To determine the amount of noise reduction afforded by a hearing protection device for the A weighted scale, OSHA recommends that 7 dB be subtracted from the NRR. This new NRR should be subtracted from the individuals time weighted average noise exposure. It must then be determined if the attenuation is appropriate for the level of noise the individual is exposed to.
There are several fit testing devices on the market that will measure the attenuation an individual receives when wearing their HPD. These systems typically use one of two methods to verify fit. The individual wears their HPD and a microphone is placed inside the ear canal and another microphone is placed outside of the ear. A sound is played and the difference between the microphones is the attenuation for that individual, known as the personal attenuation rating. In the second method, a series of sounds are played for the individual, and the lowest level that they can detect the sound is recorded. The individual then wears the HPD and the same sounds are played. The amount that the sound has to be increased so that the individual can hear it is the PAR.

Audiometric testing program

is used to determine hearing sensitivity and is part of a hearing conservation program. This testing is part of the hearing conservation program that is used in the identification of significant hearing loss. Audiometric testing can identify those who have permanent hearing loss. This is called noise-induced permanent threshold shift.
Completing baseline audiograms and periodically monitoring threshold levels is one way to track any changes in hearing and identify if there is a need to make improvements to the hearing conservation program. OSHA, which monitors workplaces in the United States to ensure safe and healthful working conditions, specifies that employees should have a baseline audiogram established within 6 months of their first exposure to 85 dBA time-weighted average. If a worker is unable to obtain a baseline audiogram within 6 months of employment, HPD is required to be worn if the worker is exposed to 85 dBA or above TWA. HPD must be worn until a baseline audiogram is obtained. Under the MSHA, which monitors compliance to standards within the mining industry, an existing audiogram that meets specific standards can be used for the employee's baseline. Before establishing baseline, it is important that the employee limit excessive noise exposure that could potentially cause a temporary threshold shift and affect results of testing. OSHA stipulates that an employee be noise-free for at least 14 hours prior to testing.
Periodic audiometric monitoring, typically completed annually as recommended by OSHA, can identify changes in hearing. There are specific criteria that the change must meet in order to require action. The criterion most commonly used is the standard threshold shift, defined by a change of 10 dB or greater averaged at 2000, 3000, and 4000 Hz. Age correction factors can be applied to the change in order to compensate for hearing loss that is age-related rather than work-related. If an STS is found, OSHA requires that the employee be notified of this change within 21 days. Furthermore, any employee that is not currently wearing HPD is now required to wear protection. If the employee is already wearing protection, they should be refit with a new device and retrained on appropriate use.
Another determination that is made includes whether an STS is "recordable" under OSHA standards, meaning the workplace must report the change to OSHA. In order to be recordable the employee's new thresholds at 2000, 3000, and 4000 Hz must exceed an average of 25 dB HL. MSHA standard differs slightly in terms of calculation and terminology. MSHA considers whether an STS is "reportable" by determining if the average amount of change that occurs exceeds 25 dB HL. The various measures that are used in occupational audiometric testing allow consistency in standards within workplaces. Completing baseline and follow-up audiograms allows workplaces to detect hearing loss as early as possible and determine whether changes need to be made to provide a safe working environment for their employees.