Requirements have been established to provide guidelines for compliance with 29 CFR 1910.95, the Occupational Safety and Health Administration (OSHA) rules for noise exposure for general industry.  A permissible exposure limit (PEL) became effective April 28, 1971.  Rules for hearing protection programs (HCP) became effective March 1, 1984.

These  requirements address State employee activities that are regulated under the OSHA general industry noise standard.  The OSHA noise standard for construction, 29 CFR 1926.52, requires that employers identify construction workers who routinely receive 100% or more of the PEL and comply with these three standards:

· 29 CFR 1926.21(b)(2): Training on recognition and protection against noise
· 29 CFR 1926.52:    Use of  or administrative controls to reduce noise if feasible
· 29 CFR 1926.101:   Use of hearing protection when controls are not feasible

Hearing conservation programs are not mandatory in construction and agricultural operations.
However, all State agencies, departments, and universities, even a department such as the Department of Transportation which engages primarily in construction activities, have elected to comply with the general industry standards, including HCPs.  For that reason, these requirements are limited to a discussion of general industry rules.

The PEL or criterion level enforced by OSHA is a function of time and loudness and is equivalent to an 8-hour time weighted average exposure (TWA) of 90 dBA.  (The dBA is the A-weighted sound level in decibels.)  The PEL is the dose most workers can receive 8 hours a day, 40 hours a week, over a 40-year working life without significant hearing loss.  Attachment 1, taken from the OSHA noise regulation, shows relationship between time and noise level.  For every increase of 5 dBA, the permissible time of exposure is cut in half.  Therefore, while the PEL at 95 dBA is reached in 4 hours it takes only 2 hours at 100 dBA to reach the PEL.

The OSHA noise regulation states that 140 decibels should not be exceeded but OSHA does not enforce this limit.  The limit is based on the assumption that there is a “critical level”, a level above which there is high risk, no matter how short the duration might be.

OSHA set the permissible daily dose to guard against material hearing impairment even if the worker is exposed for a 40-year working lifetime.  It is generally agreed that the capacity to hear and understand speech is the most critical function of human hearing.  OSHA used field data to predict excess hearing loss (see Attachment 2) resulting from steady exposure to broad band noise every day, eight hours a day, over periods of up to 40 years to establish a permissible daily dose.  There is no comparable data for intermittent noise exposure of short duration such as is typical of construction work.

Chronic noise-induced hearing loss is a permanent sensorineural condition that cannot be treated medically.  It is initially characterized by a declining sensitivity to high-frequency sounds, usually at frequencies above 2000 Hertz (Hz).  (A hertz is the number of times per second a sound wave repeats itself.)

Exposure of a person with normal hearing to workplace noise at levels equal to or exceeding the PEL may in time cause a shift in the worker’s hearing threshold.  Such a shift is called a standard (or significant) threshold shift and is defined as a change in hearing thresholds that averages 10 dB or more at 2000, 3000, and 4000 Hz in either ear.  Workers experiencing significant threshold shifts are required by OSHA to be fitted with hearing protectors and to be trained in their use.

In addition to effects on hearing, noise may:

· Interfere with speech
· Cause a stress reaction
· Interfere with sleep
· Lower morale
· Reduce efficiency
· Cause annoyance
· Interfere with concentration
· Cause fatigue

While no specific disease is associated with noise exposure except hearing loss, not all hearing loss is caused by over-exposure to noise.  Loss of hearing may result from disease or infection, an accident, smoking, medicines and drugs, heredity, loud music, hobbies such as woodworking, or simply from age.  Dramatic events like explosions and blows to the head can rupture ear drums, damage bones, and destroy hair cells.  Sportsmen and gun buffs can damage their hearing by firing rifles without using hearing protection.

Hearing loss due to noise damage, as opposed to age for example, can usually be identified because the loss, at least in the early stages, is most severe in the high frequencies.  The 4000-hertz “dip” shown in an audiogram is typical of noise damage.  When hearing degenerates with age, sounds overall become quieter and less clear and background noise becomes an interference.  People don’t usually become materially impaired by aging alone, however, unless they live to be very old, in their eighties.  Hearing loss due to noise and loss due to aging are both permanent.

Two noises having identical sound levels but comprised of different frequencies usually are not equally dangerous.  Most dangerous are the frequencies between 1500 and 4000 Hz.  While high pitched noise is more damaging than low pitched noise, there has been no authenticated case of hearing loss due to exposure to noise of ultrasonic frequency.  High frequency noise is, however,  more annoying than noise at lower frequencies.  The most annoying noise is high-pitched, loud, and irregular or on-and off.  Intermittent noise is, however, less damaging than steady-state noise.

As shown in Attachment 2, a person exposed to 100% of the permissible daily dose (90 dBA as an 8-hour TWA), 40 hours a week over a 40 years can be predicted to  have an average loss of 12 decibels in the speech frequency range (500, 1000, and 2000 Hz).  This is not considered material hearing impairment.  Material hearing impairment is defined as an average loss that exceeds 25 decibels in the frequencies 1000, 2000, and 3000 Hz in either ear.  People who have material hearing impairment have difficulty understanding speech as it is spoken in ordinary social situations.  Levels of material hearing loss are described in Attachment 3.

Noise-induced hearing loss can be temporary or permanent.  Temporary hearing loss, also called temporary threshold shift, results from short-term exposures to noise, with normal hearing returning after a period of rest.  Generally, prolonged exposure to high noise levels over a period of time causes a permanent threshold shift.  A standard threshold shift (STS) is an average permanent change in either ear of 10 decibels at 2000, 3000, and 4000 Hz or more relative to the baseline audiogram.  Employees who have experienced an STS need to reduce their noise dose to no more than 50% of the permissible daily dose.

A hearing aid can make speech louder, but cannot make it clearer, and is rarely a satisfactory remedy for nerve damage produced by noise induced hearing loss.  Employees should be required to remove hearing aids and insert earplugs in noisy areas.

According to the ACGIH,. exposure to certain chemicals may result in hearing loss.  In settings in which there may be exposure to noise as well as to toluene, lead, manganese, or n-butyl alcohol,  the ACGIH recommends periodic audiograms.  Other substances under investigation for ototoxic effects include trichloroethylene, carbon disulfide, styrene, mercury, and arsenic. Ototoxic drugs primarily affect the hair cells.

Researchers at the University of Wisconsin Medical School reported in JAMA, June 3, 1998  that smoking may harm your ability to hear.  The study revealed that smokers were nearly 1.7 times more likely to suffer hearing loss than were nonsmokers.  In addition, a smoker’s chances of hearing loss increased in relation to the amount he or she smoked.

TTS may be caused by use of aspirin or other drugs.

OSHA requires that when workplace exposures routinely exceed 100% of the PEL, feasible engineering or administrative controls must be used.  OSHA considers engineering and administrative controls feasible if they are feasible technically and the costs are less than the cost of a HCP.  An alternative approach is to manage worker’s time on the job so that noisy work periods is offset by enough quiet time so the PEL is not be exceeded.

Reductions in the order of 50 decibels are possible with enclosures.  The amount of reduction depends on the transmission loss of noise through the enclosure and the amount of noise absorbed by the enclosure lining.  For example, if a 30#/sq ft concrete enclosure is lined with material that is a good absorber, say 1 inch of sprayed-on mineral fiber, the noise reduction will be in the order of 45 decibels.  The transmission loss can be increased by about 6 decibels for each doubling of the mass.

Noise absorbent materials on room surfaces can reduce the noise level in the hearing zone of an employee working near a noise source in the  room by roughly 3 to 6 decibels.  If the noise source near the employee is the only source of noise contributing to his dose, the maximum reduction would be 3 decibels.  If, however, part of his noise dose is due to other noisy sources in the room, reducing the  reflected sound could result in more than a 3 decibel reduction at his workplace, perhaps a reduction in the order of 6 dBA.  The sound level could be reduced by 10 to 20 decibels in areas of the room some distance from all noise sources, however.  This illustrates why employees need to put as much distance as possible between themselves and noise sources.  Noise levels decrease 6 decibels for every doubling of distance.

Since dose depends on duration and intensity of exposure, administrative controls can be used to reduce the daily dose by limiting exposure time.  Administrative controls work if employees can be rotated.

Some facilities post signs in areas or by equipment warning that noise levels can exceed 85 dBA.  In the past, signs have been used as a means of training employees about noise hazards.  OSHA, however, decided that warning signs sometimes confuse rather than serve a useful education purpose and that training is a better way to inform workers of the hazards of noise to their hearing than signs.  In the case of infrequently visited high noise areas, however, use of warning signs stating that hearing protection is required may be the best solution.

Until 1983, when the 1983 Hearing Conservation Amendment was passed, OSHA enforced engineering and administrative controls to modify the source creating the noise or alter the worker’s environment to reduce the exposure.  Since 1983, OSHA has shown a tendency to enforce the Hearing Conservation Amendment instead of other parts of the noise regulation.  The amendment requires employers (except agriculture and transportation) to administer a continuing, effective hearing conservation program for employees whose noise exposures equal or exceed an 8-hour TWA of 85 dBA or, equivalently, for employees whose noise dose  is equal to 50% of the PEL.  This program must include all employees whose work brings them, either routinely or intermittently, into areas in which the sound levels exceed those permitted in Table G-16a of the standard.  Employees who work less than four months (<120 days) are not covered by the amendment.

The five elements of an OSHA hearing conservation program are:
· Monitoring, employee notification, and observation of monitoring
· Audiometric testing programs and test requirements
· Hearing protectors and hearing protector attenuation
· Training program and access to information and training materials
· Recordkeeping

Attachment 6 is a generic hearing conservation program.

Monitoring is required if there are indications that 50% of the PEL is exceeded.  When screening for noise exposures, sound level meter measurements and estimates of exposure duration are sufficient.  The resulting spot readings can be used to determine the need for a more complete evaluation.  If the results of the screening indicate that the noise standard may be exceeded, the noise exposures of representative employees from each job classification potentially overexposed need to be monitored using a dosimeter with a threshold of 90 dBA to determine compliance with 29 CFR 1910.95(a) and (b) as well as one with a threshold of 80 dBA to determine compliance with 29 CFR 1910.95(c).  The OSHA noise standard requires that impulsive, as well as continuous and intermittent sound levels be included to determine inclusion in the HCP.  Only instruments using a 5-dB exchange rate set on slow response may be used for OSHA compliance measurements.

The hearing conservation amendment has an entirely different criterion for noise measurement than the portion dealing with engineering and administrative controls.  The HCA requires the measurement and integration into the TWA of all noise between 80 dBA and 130 dBA.  This includes steady state, intermittent, and impulsive noise.   Therefore, two criteria must be considered when designing or retrofitting workplaces to comply with OSHA:

1. An administrative and engineering control requirement to meet 90 dBA TWA when measurements start at 90 dBA.
2. A HCP when exposures equal or exceed 85 dBA TWA with measurements starting at 80 dBA.

The 80-dBA threshold reading measures the noise dose of employees whose exposure may exceed the levels specified in Table G-16a of the standard that trigger enrollment in a hearing conservation program.  The 90-dBA threshold reading measures the noise dose of employees whose exposure may exceed the PELs in Table G-16 of the general industry standard (1910.95) or Table D-2 of the construction standard (1926.52).

Monitoring results are reported in dBA.  The decibel (dB) is a unit of intensity of sound and is a measure of the sound pressure level.  It is perceived as loudness.  Doubling the sound pressure corresponds to an increase of 6 decibels.  The A-weighted response on the sound level meter or dosimeter is designed to approximate the responses of the human ear.  The ear is most responsive to frequencies between 500 and 2000 hertz; e.g., forty decibels at 1000 hertz sounds is just as loud as fifty decibels at 100 hertz.  Accordingly, the A-weighted decibel reading (dBA) is weighted in favor of frequencies between 500 and 2000 hertz and discriminates against frequencies less than 500 hertz.

Some dosimeters indicate when a 115 dBA sound level has been exceeded.  This indication is not used for compliance purposes.

Employees who receive a daily dose equal to or greater than an 8-hour TWA of 85 dBA need to be notified of the results of monitoring.  Employees must also be given the opportunity to observe monitoring.

Use an impact-noise meter with peak hold capability to measure impact noise.  The inertia of the indicating meters of general-purpose sound level meters prevents accurate, direct measurements of single-impulse noises that change level significantly in less than 0.2 second.  A low inertia device such as an oscilloscope must be used to measure these impulse-type noises if detailed information is required.

The impulsive noise exposure limit of 140 dB peak  of the 1972 OSHA regulation does not specify a limit for the number of impulses that a person can be exposed to in an 8-hour working day, but it can be expected that a limit such as 100 impulses for 8 hours may be set sometime.  Perhaps different peak level limits will be specified for a greater number of impulses.

Audiometric testing includes baseline audiograms, annual audiograms, training, and follow-up procedures.  It is not adequate or safe to believe a HCP is satisfactory merely because a van and technician visit a plant annually and perform audiometric tests that are simply filed into the employee’s record.  This system actually instills a false sense of security since it does not prevent hearing loss; it merely provides computerized data that are often of little use and perhaps not even understood by personnel in some agencies.  Such a program chiefly documents the liability of the agency or university.

Hearing tests are useful because they can detect mild hearing loss before damage is obvious or disabling.  Audiograms show the results of hearing tests.  They show how intense or loud a sound must be before an employee hears it  With annual hearing tests it is possible to trace and document hearing loss, and by so doing to prevent further loss from occurring.  Test results can also be used to indicate whether or the HCP is preventing hearing loss.  Test results must be kept for the duration of the employee’s employment.

While exposure to the permissible daily dose 8 hours a day, 40 hours a week, without benefit of hearing protectors for 10, 20, 30, or even 40 years does not result in material hearing impairment, it is predicted that 10% of employees so exposed will experience a STS of 10% within 10 years.  (See Attachment 2)  If hearing tests show an STS has occurred, the employee must be informed within 21 days and counseled about further evaluation.  The employee must also be given additional training about use of hearing protectors. In determining whether a STS occurred, allowance may be made for aging (presbycusis).

As a rule, revision of a baseline audiogram is not permitted for rehired employees.  North Carolina OSHA states, however, that the employer may line out an entry on the OSHA log if the employee’s period of non-employment is greater than one year and a termination audiogram exists.  The rationale for lining the employee out is that he was not exposed to 85 dBA as an 8-hour time-weighted average for that employer in the previous year.  The rationale for having a termination audiogram is to make sure the change did not occur between the first test and termination.

Employers need to enforce use of hearing protectors if employees:

· Receive a dose equal to or greater than the permissible daily dose.
· Receive a dose  at or above 50% of the permissible daily dose if they have to wait longer than 6 months to receive their baseline audiograms.
· Have incurred work related standard threshold shifts.

Employer also need to make hearing protectors available at no cost to employees routinely exposed to 50% or more of the permissible daily dose.

Basic styles of HPDs in common use include earplugs that are inserted into the ear canal, ear canal caps that seal the canal at or near its rim, and earmuffs that encircle the outer ear.  The basic HPDs produce attenuation of noise strictly by passive means without the use of electronic circuitry and include use of materials with high sound-transmission loss properties, liner materials that absorb and dissipate sound, trapped air volumes that provide acoustical impedance, and compliant materials that establish an acoustical seal against the skin.  When properly selected for the situation and correctly worn, they provide adequate protection in most environments.  However, due to the very nature of the attenuation they provide, they often have an effect on hearing quality and perception.

Special HPDs provide both acceptable attenuation and augmented auditory perception.  Technologies which incorporate electronics to achieve such features as noise cancellation, signal transmission, or DC-powered communications capabilities are typically termed “active,” while those that rely strictly on mechanical means to provide various qualities such as amplitude-sensitive or uniform attenuation are termed “passive.  Active noise reduction relies on the principle of destructive interference of equal amplitude but exactly out-of-phase sound waves at a given point in space.  In the case of HPDs the cancellation is established at the ear.  There are 2 types:  Those designed solely for hearing protection and those designed for 1- or 2-way communication having the associated boom-or throat-mounted microphone and earphone components, commonly referred to as headsets.

The active and passive designs can provide valuable performance advantages to potentially ameliorate situations such as employees needing less attenuation to hear well, overcoming the spectral distortion typical of conventional HPDs, or providing attenuation that dynamically changes with sound level.  When considering specialized HPDs, account must also be made of their increased costs and potential reduced reliability compared with the conventional HPD alternatives.

The only certain means for evaluating the effectiveness of personal protectors is to measure periodically the hearing thresholds of the user.  If no hearing losses are observed--other than those due to the aging process--the program my be considered to be successful.  However, a hearing monitoring program may take years to become meaningful because noise-induced hearing loss usually develops slowly.  Protective noise reduction characteristics, or attenuation values, must be used as a short-term guide in the selection of the personal hearing protection equipment for particular noise exposure patterns.

An employee’s deliberate failure to wear hearing protection is not the agency’s responsibility and the agency will not be cited for the employee’s misconduct providing the requirements of the HCP are complied with and that compliance is documented.

The adequacy of ear protection depends upon the tightness of the fit and its use by employees.  Foam plugs come in one-size that fits everyone and they offer as much protection as rigid plugs.  Employees do, however, need training on how to insert them properly.  The correct size of molded or rigid earplugs is vital. Cotton or various swimmer’s ear plugs provide relatively little protection against dangerous noise.  Hearing protectors do not always provide as much attenuation in practice as the manufacturer indicates.  OSHA states (46 FR 4078, January 16, 1981) that ear plugs tested in industrial settings will provide a mean attenuation of about 10 decibels.  Given the present state of the art, hearing protectors which offer the greatest attenuation may not reliably reduce exposures to safe levels when an average dose borders on 100 dBA as an 8-hour TWA; i.e., when exposure is more than four times the OSHA permissible daily dose.  (Reference:  OSHA INSTRUCTION CPL 2-2.35A)  The combination of plugs and muffs increases attenuation approximately 5 decibels for a total of 15 dBA.

Ear protectors do not  make it more difficult to carry on a conversation and hear warnings when noise is above 80 decibels.  When noise ranges from 85 to 105 decibels, hearing is actually improved when plugs or muffs are used.  This improvement occurs because the levels of both the speech and noise are reduced to where the hearing mechanism is not overloaded and it is relatively free from distortion caused by high levels of sound.  When noise is below 80 decibels, earplugs may reduce the intelligibility of face-to-face communication because the speech level may fall below the hearing threshold.  There is some change in sound quality when plugs or muffs are used but employees can be expected to quickly adjust to this change.

Employees who are exposed to intermittent noise may not always know when ear protectors are needed.  As a rule of thumb, if employees have to raise their voice to be heard by someone less than 2 feet away, they need to use ear protectors.  By directing sound into the ear, headphones can produce levels loud enough to damage hearing.  Headphone users need to hold their head sets an arm’s length away.  If they can hear the sound, the volume is probably too high.

OSHA requires the employer to:

· Schedule employees who receive 50% or more of the permissible daily noise dose in a training program at the  time of initial assignment and annually thereafter.
· Make sure that training contains, as a minimum, these elements:  (1) the effects of noise on hearing; (2) the purpose of hearing protectors, the advantages, disadvantages, and attenuation of various types, (3) instructions on selection, fitting, use and care; and (4) the purpose of audiometric testing and an explanation of the test procedures.  Training videos can be used but an instructor needs to be immediately available to trainees so that they have the opportunity to obtain interactive answers to their questions.
· Schedule additional training when new exposures are created.
· Make a copy of 29 CFR 1910.95 available to employees (e.g., post a copy in the workplace).
· Provide a copy of 29 CFR 1910.95 to employees exposed to 50% or more of the permissible daily dose should they ask for it.
· Provide copies of training materials to OSHA on request.

Ultrasound is high frequency sound that is inaudible to the human ear.  The frequency audibility limit of the human ear is about 20 kilohertz (kHz).  The frequency limit normally declines with age.  Most of the audible noise associated with ultrasonic sources, such as ultrasonic welders or ultrasonic cleaners, consists of subharmonics of the machine’s fundamental ultrasonic frequencies.  For example, many ultrasonic welders have a fundamental operating frequency of 20 kHz.  However, a good deal of noise is also present at 10 kHz, the first subharmonic frequency of the 20 kHz operating frequency, and is therefore audible to most persons.  Research indicates that ultrasonic noise has little effect on general health unless there is direct body contact with a radiating ultrasonic source.  Reported cases of headache and nausea associated with airborne ultrasonic exposures appear to have been caused by high levels of audible noise from source subharmonics.

Individual risk factors and other exposures explain the large variation in the development of noise-induced hearing loss (NIHL).  Such factors include heredity, cholesterol, blood pressure, vibration induced white finger symptom, painkillers, smoking, and exposure to organic solvents.  Hearing loss may occur without noise exposure.  While age has a lower significance than previously thought, the large variation in NIHL is mostly explained by individual vulnerability factors which are age dependent.

Encouraging employees to take their earplugs home and use them during noisy recreational or other activities will reduce the likelihood of compensation claims by reducing employee hearing loss.   Noisy off-the-job activities include home power tool use, lawn and garden care, commercial air travel, nightclub and sporting events attendance, visits to state fairs, theme parks, etc.

Employees may want to test their hearing to see if their off-the-job exposures are causing hearing loss.  There are  two tests that concerned employees can perform.  The first one developed by the American Academy of Otolaryngology is shown in Attachment 4.  Another quick test is offered by the Occupational Hearing Services.  An employee can dial 1-800-222-EARS weekdays between 9:00 am and 6:00 pm to hear a two-minute recorded telephone test  The record plays a series of quiet tones.  If the employee can’t hear all eight of them, he will be advised to get a more complete hearing exam.  Before calling, the employee needs to make sure that he is using a good quality telephone and is in a quiet room with the TV and air conditioner off.

OSHA requires employers to:

· Keep training records for two years that include training dates, contents of training, name and qualifications of the trainer, and names and job classifications of the trainees.
· Keep audiometric test records for the duration of the employee’s employment that include the employee’s name and job classification, date of the audiogram, the examiner’s name, date of the last acoustic or exhaustive calibration of the audiometer, and the employee’s most recent noise exposure assessment.
· Keep records of the background sound pressure levels in audiometric test rooms for the duration of the employee’s employment.
· Provide training and test records to employees on request.
· Log standard threshold shifts as illnesses on the OSHA 200 form.  According to North Carolina OSHA, if hearing loss is work related (i.e., the employee’s daily noise dose is equal to or greater than the OSHA permissible daily dose) and there is a 10 decibel or greater standard threshold shift in either ear, the hearing loss is a recordable illness.  Federal OSHA proposed on February 2, 1996, that any work-related case resulting in an average shift of 15 decibels or more at 2000, 3000, or 4000 Hertz in one or both ears as measured from the employee’s original baseline be logged.  In the OSHA proposal, the hearing test may be adjusted for aging and the recorded case may be removed if a retest performed within 30 days does not confirm the original shift.  OSHA states a presumption of work-relatedness is used for hearing loss occurring to employees who are exposed to noise levels above 85 dBA as an 8-hour time-weighted average and proposes that a shift of 10 dB be used as the action level.

Eligibility for workers’ compensation is described in G.S. 97-52 (see Attachment 5).  Employees can collect workers’ compensation only when their hearing loss is work related.  As described above, there are many causes for hearing loss besides prolonged exposure to loud noise at work. Exposure monitoring serves to verify whether or not noise in the workplace is the basic cause of hearing loss.  Claims are denied when the employee’s routine daily dose is documented as being below the OSHA permissible daily dose.  Contributory negligence bars a worker’s recovery of compensation; e.g. in one case although the employer should have known noise levels were potentially harmful, the employee’s hunting without using hearing protection for over 20 years barred recovery for hearing loss.

In its Occupational Noise exposure Revised Criteria  for 1998, NIOSH has moved away from the current OSHA position of dual action and criterion levels, going instead with a single recommended exposure limit of 85 dBA.  The rationale is to offer greater protection to noise-exposed workers, citing research that indicates an 8% excess risk of hearing loss at the 85 dBA TWA limit as opposed to 25% at 90.

· Use of the 3 dB exchange rate.
· Providing for exposure up to 140 dBA, with allowable exposure times falling to less than 1 second.  This could be interpreted as raising the default exposure ceiling limit to 140 dB.  By publishing exposure tables that provide no allowable time at any exposure above 115 dBA, OSHA effectively adopted that value as a ceiling limit.
· Exposure monitoring every 2 years.
· A “dose” approach for hearing protection with hearing protection devices (HPD) to be selected on the basis of 8-hour TWA rather than sound level.  The protection design goal for HPD has been dropped to 85 dB for all exposed workers from OSHA’s current dual criteria of 90 dB for most workers and 85 dB for those with STS.
· Assessing HPD effectiveness, or “derating”, using a variable scheme based on the type of protector.  Earmuffs are expected to provide 75% of the EPA NRR in field use, resulting in a 25% derating.  Formable plugs are assumed to offer half the NRR, with a 50% derating, and all other plugs are assumed to offer 30% of their NRR rating.
· Changing the definition of a STS by eliminating frequency averaging in calculation of that hearing loss requiring follow-up.  The new definition is “15 dB twice,” or a shift for the worse of 15 dB at any test frequency confirmed to be persistent by a follow-up test.
· Eliminating presbycusis “correction” under the premise that adjusting hearing test results for age “masks” hearing loss until it’s too late for intervention and prevention
· Two hearing tests per year for works exposed to 100 dBA or greater.
· Use of administrative controls shall not result in exposing more workers to noise.
· An annual review of hearing-test data as the definitive measure of hearing-loss prevention program effectiveness.  The test of effectiveness is to compare the incidence of hearing loss in the exposed workforce to a control population.  If hearing loss is occurring in the exposed group at a rate equal to or less than the control, the program is deemed effective, and vice versa.   Barring the availability of “more appropriate data” such as hearing tests on a local, non-noise exposed population, NIOSH suggests using Annex C of ANSI S3.44-1996 as the control.

John Franks, NIOSH noise expert, has defined “regular” exposure to 85 dBA as one day or more a month unless a worker is exposed to over 110 dBA for any length of time in which case the dose doesn’t matter anymore.  According to Mr. Franks, workers such as firefighters, medical emergency responders, policemen who fire weapons, etc., need to be enrolled in a hearing conservation program because, based on anecdotal data, these workers can experience abrupt changes in hearing.  They can go along for years without a change and then all of a sudden experience abrupt loss.

The ACGIH states:

The ACGIH  threshold limit values (TLVs) refer to sound pressure levels and durations of exposure that represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect on their ability to hear and understand normal speech.  Due to individual susceptibility the TLVs should be used as guides and not regarded as fine lines between safe and dangerous levels.  The  TLVs should protect the median of the population against a noise-induced hearing loss exceeding 2 dB after 40 years of occupational exposure .  A hearing conservation program with all its elements including audiometric testing is necessary when workers are exposed to noise at or above the TLV levels.  For impulses above a C-weighted peak of 140 dB, hearing protection should be worn.  The MIL-STD-1474C provides guidance for those situations in which single protection (plugs or muffs) or double protection (both muffs and plugs) should be worn.

The TLVs for noise are tabulated in Attachment 7.

DOT enforces Vehicle Interior Noise Standards as part of the DOT Motor Carrier Safety Regulations. (DOT-FHWA:  Vehicle Interior Noise Levels, 38 FR 30880, 1973, 49 CFR 393.94).  They specify the maximum sound pressure level of 90 dBA at the operator’s ear position determined under stationary test with the transmission in neutral and the engine operating at its maximum speed.  Major noise sources are the exhaust, intake, and engine.  Tire noise is generally insignificant.

A noise level of up to 45-dBA background is generally acceptable in small offices.

Employers who permit use of personal entertainment devices (PEDs) with headphones in the workplace cannot be certain that exposure on the job is less than 90 dBA TWA.  Depending on the program content, music (as opposed to talk radio), and personal preference, users will set the volume on PEDs between 3 and 15 dB over the ambient sound level.  Since the employer is responsible for noise exposure on the job, if he permits workers to use PEDs at unknown and uncontrolled levels, he is basically giving the responsibility for noise exposure control to the worker and the employer would probably be held liable for hearing loss for failure to effectively carry out feasible noise control measures. This is one of the reasons many employers prohibit the use of these devices while at work.

The US Postal Service, however, has developed special ear muffs equipped with volume-limited music for use in monotonous high noise jobs to protect employee hearing but at the same time allowing them to enjoy background music.  Such devices are in compliance with OSHA regulations if they meet the attenuation requirements relative to the workplace noise levels and their average music output is less than 90 dBA.  In another case, at a Volvo plant where the noise is between 95 and 100 dBA, “musical muffs” are issued .  The level of the music is maximized at 82 dBA.  The sound waves of the music are conducted to the muffs by magnetic fields in the ceiling.  They work well as ear protectors.