Hearing conservation program
Hearing conservation programs are design to prevent noise induced hearing loss.  A written hearing conservation program is required by the Occupational Safety and Health Administration (OSHA) 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.   While the Mine Safety and Health Administration (MSHA) also requires a hearing conservation program, MSHA does not require a written hearing conservation program.  MSHAs hearing conservation program requirement can be found in 30 CFR  62.150, and requires has almost the same exact requirements as the OSHA hearing conservation program requirements.  Therefore, only the OSHA standard 29 CFR 1910.95 will be discussed in detail.

# Program requirements
The OSHA standard contains a series of program requirements.
- Engineering Controls: 29 CFR 1910.95(b)(1) 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...
- Monitoring: 29 CFR 1910.95(d) requires that monitoring be conducted when any employees exposure may equal or exceed an 8-hour time-weighted average of 85 decibels.
- Testing: 29 CFR 1910.95(g) 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(i) 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(k) 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(m) 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.  This type of survey is normally completed using a sound level meter (SLM).  There are three types of sound level meters.  Type 0 is precision instrument normally used in laboratories.  A 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.  Noise monitoring is generally completed using a noise dosimeter that integrates all continuous, intermittent and impulsive sound levels to determine a persons noise exposure level.
Surveys must be repeated when there are significant changes in machinery and/or processes that would affect the noise level.

# Administrative and engineering controls
Administrative and engineering controls are the preferred method to prevent noise exposure.  Normally, administrative and engineering controls do not require personal protective equipment and therefore are normally more protective.  However, it is not always feasible to use administrative and engineering controls as the only ways to prevent noise over-exposure.  The key is to maintain an 8-hour time-weighted average of less than 85 dBA so that personal protective equipment is not required.

# Hearing protection device
If engineering controls fail to maintain an 8-hour time-weighted average below 85 dBA, then a hearing protection device (hpd) is required.  There are two general types of hpds: earplugs and ear muffs.  Each one has its own benefits and drawbacks.  The selection of the proper hpd to be worn is commonly done by an  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: premolded, 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 users 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
Earmuffs 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  to help reduce noise exposures.

# Noise reduction ratings
The United States Environmental Protection Agency (EPA) requires that all hearing protection devices be labeled with their associated noise reduction rating (NRR).  The NRR provides the estimated attenuation of the hearing protection device.  However, it has been found that the labeled manufacturers' noise reduction ratings (NRRs) substantially overestimated the actual field attenuation performance.  To determine the amount of noise reduction afforded by a hearing protection device, OSHA recommends that 7 db be subtracted from the NRR.  The NRR is generally given in a C-weighted format, so to obtain the A-weighted reduction, one must subtract 7 db.  OSHA also recommends a 50% safety factor, therefore the final OSHA recommended reduction would be (NRR-7)/2. 

# Audiometric testing program
Audiometric testing is a very important part of a hearing conservation program.  Audiometric testing allows for the identification of those that have lost significant hearing.  Additionally, the testing allows for the identification of those who are in process of losing their hearing.  Audiometric testing is most important in identifying those who have permanent hearing loss.  This is called noise-induced permanent threshold shift (NIPTS) 

# Employee training and education
Proper training and education of those exposed to noise is the key to preventing noise-induced hearing loss.  If employees are properly trained on how to follow a hearing conservation program, then the risk of noise-induced hearing loss is reduced.  OSHA requires said training to be completed on an annual basis.  Proper training is imperative since even with a very modest amount of instruction attenuation performance can be significantly improved.

# Record keeping
OSHA requires that records of exposure measurements and audiometric tests be maintained.  Records are also required to have the following:
- name and job classification
- date of the audiogram
- examiners name
- calibration date
- employees most recent noise exposure assessment
- background sound pressure levels in audiometric test booths.
Noise exposure measurement records must be maintained for at least 2 years.  Audiometric test records must be retained for the duration of the affected employees employment.  Additionally, employees, former employees, representatives designated by the individual employee and the Assistant Secretary all must have access to these records.

# Program evaluation
Proper program evaluation is important in maintaining the health of hearing conservation program.  The National Institute for Occupational Safety and Health (NIOSH) has created a checklist to help evaluate the effectiveness of a hearing conservation program.  It can be found on their website.  NIOSH recommends that fewer than 5% of exposed employees should have a 15 dB Significant Threshold Shift in the same ear and same frequency.