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By David S. Cmar & John C. Dolehanty

Winter 2006

When most people think of Hearing Conservation Programs there are two aspects that come to mind, ear plugs and hearing tests.  Audiometric test results, when properly reviewed, are an extremely important part of a Hearing Conservation program.  The test is primarily a trailing indicator, and does not in and of itself prevent hearing loss.  However, the test is a critical metric by which the results of the proactive parts of a program (Engineering and Hearing Protection) are judged.  When the information used to obtain test results is both accurate and reliable, it can help to validate the effectiveness of a program, or identify if additional efforts are necessary to protect employees hearing. 


When is Audiometric Testing Necessary? Who gets Tested?

Many jurisdictions in North America require audiometric tests to be preformed by employers.  The criteria for determining who gets tested and at what point in time varies depending on governing body.  In the US, the requirements are federally mandated (either by OSHA, MSHA or the US Military) and are quite specific.  Employees identified as being exposed to levels above 85 dBA TWA8HR are required to have an initial baseline audiogram and then repeat testing on an annual basis.  In Canada, legal requirements vary from province to province.  In general, audiometric testing is required in the provincial health and safety regulations, but may also be required through worker’s compensation insurance regulation.  The following table outlines the requirements across North America and provides links for further information. 








90 dBA

85 dBA

29 CFR - Occupational noise exposure. - 1910.95(g)



90 dBA

85 dBA

30 CFR PART 62—Occupational Noise Exposure


US Military

90 dBA

85 dBA

DODI 6055.12 DOD Hearing Conservation Program


US Navy

84 dBA

84 dBA

Navy Environmental Health Center Technical Manual NEHC – TM 6260.51.99-2 (September 2004)


US Army

85 dBA

85 dBA

DA PAM 40-501 Hearing Conservation (1998)


US Air Force

85 dBA

85 dBA

AFOSH Standard 161-20 Hearing Conservation Program (OCT 91)



Federal Employees

87 dBA


Canada Occupational Health & Safety Regulations (SOR 2002-208) Part VII Levels of Sound



85 dBA

85 dBA

Alberta Occupational Health & Safety Code Section 223(1)


British Columbia

85 dBA

85 dBA

B.C. Reg. 382/2004, effective January 1, 2005 (OHSR Part 7)



85 dBA

80 dBA

Manitoba Regulation 227/94, The Hearing Conservation and Noise Control Regulation


New  Brunswick

85 dBA


General Regulation (N. B reg. 91- 191 as amended) Part V, Section 29



85 dBA (AGCIH)


Occupational Health and Safety Regulations under theOccupational Health and Safety Act (O.C. 96-478)


Nova Scotia

85 dBA


Nova Scotia Occupation Health & Safety Regulations





Province of Ontario R.R.O. 1990, Reg. 851 s.139


Prince Edward Island

85 dBA

85 dBA TWA8HR (Also criteria for impact noise above 120 dBA)

Occupational Health & Safety Act, Part 8 Noise



90 dBA





85 dBA

85 dBA Lex or Levels above 90 dBA on a regular basis

Occupation Health & Safety Regulations, 1996 Part VIII Noise Control and Hearing Conservation


Yukon Territory

85 dBA

80 dBA Lex or 135 dB Lpk



Northwest Territory

85 dBA




Nunavut Territory

85 dBA





What is an Audiometric Test and How is Noise Induced Hearing Loss (NIHL) Defined?

Although there are several ways that people may suffer hearing loss, the most common type in industry is a cumulative loss due to long-term exposure to noise levels consistently in excess of 85 dBA in the workplace.  This repeated exposure to noise causes a temporary hearing loss and eventually leads to a permanent noise induced hearing loss (NIHL).

In order understand audiometric results and the associated liabilities there are several terms associated with hearing loss that are important to defined:

Temporary Threshold Shift (TTS)
Temporary hearing loss occurs when hair cells in the inner ear have been damaged by excessive sound.  This is typically noticeable by a ‘ringing in the ears’ (tinnitus).  This typically occurs during short term exposures to high noise levels, for example at a loud concert.  If a person’s hearing was assessed immediately after this exposure, the test would show a decrease in hearing ability.  If the hearing ability returns to normal (baseline levels) after a short period of time, the shift in hearing ability is considered to be temporary, thus a Temporary Threshold Shift (STS). 

Even though the temporary loss may go away, permanent damage may have occurred in the ear and continued exposure to high noise levels may result in a permanent hearing loss.

Standard (or Significant) Threshold Shift (STS)

Standard Threshold Shift is a term defined by OSHA (US) [1910.95(g)(10)(i)] to describe a change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more at 2000, 3000 and 4000 Hz in either ear from baseline levels.  Under OSHA regulations, additional audiometric testing and follow-up is required when an employee is found to have an STS.  NIOSH also uses this term to describe a change of 15 dB or more at any frequency, 500 through 6000 Hz, from baseline levels in the same ear and at the same frequency.

Permanent (or Persistent) Threshold Shift (PTS)
A Permanent Threshold Shift (PTS) refers to the damage to the ear as a result of continued or repeated exposure to excessive noise over a period of time.  When Temporary of Standard Threshold Shifts are shown to be persistent and no recovery of hearing ability occurs, a person is said to have suffered a permanent hearing loss.

Hearing is tested by checking a person’s response to pure tone sounds in frequencies that span the major range of human hearing (250 – 8000 Hz).  The first test given to an employee is considered a ‘baseline’.  This is what future hearing ability is compared to for the purposes of quantifying hearing loss.  The majority of jurisdictions in North America focus the definition of hearing loss in 500, 1000, 2000, 3000 and 4000 Hz frequencies.  The most common criteria used in most jurisdictions is the formula recommended by the American Academy of Otolaryngology (AAO), the “AAO-79” which is also endorsed by the American Medical Association AMA which defined Hearing Impairment as an average loss greater than 25 db in 500, 1000, 2000 and 3000 Hz frequencies and the older AAO method AAOO-59 which defines Hearing Impairment as an average loss greater than 25 dB in the 500, 1000 and 2000 Hz frequencies.  Other jurisdictions use criteria similar to these, or have no specific criteria and use the concept of ‘Medical Evidence’ which relies on the discretion of the consulting physician to determine the extent of the hearing impairment. 

The following table provides a reference for methods of calculating hearing impairment in various jurisdictions.




Medical Evidence

Impairment determined by consulting physician

AL, AK, AR, DE, FL, HI, ID, IL, IN, IO,KY, LA, MA, MI, MN, MS, NH, OH, SC, TN, VT, WY, New Brunswick, Quebec, Prince Edward Island


Average loss of 25 dB or more at 500, 1000, 2000 Hz



Average loss of 25 dB or more at 500, 1000, 2000, 3000, Hz




Average loss of 28 dB or more at 500, 1000, 2000, 3000, Hz



Average loss of 30 dB or more at 500, 1000, 2000, 3000, Hz



Average loss of 35 dB or more at 500, 1000, 2000, 3000, Hz


ANSI S3.44-1996

Average loss of 30 dB or more at 1000, 2000, 3000, Hz



Average loss of 25 dB or more at 500, 1000, 2000, 3000, 4000, 6000 Hz



Implications of NIHL on Business

Aside from the obvious detrimental effects on employee’s health and abilities to communicate on the job, how does NIHL impact a business?  The direct cost can be measured in terms of dollars spent on hearing loss claims through workers compensation insurance claims or direct litigation against companies.  Because hearing loss compensation is dealt with differently in various jurisdictions in North America, complete comprehensive statistics on the cost of hearing loss claims are not readily available.  There is however some data available to indicate the magnitude of existing claims and the potential for increases in the future.

In September 2005, the Institute of Medicine (IOM) of the National Academies released Noise and Military Service: Implications for Hearing Loss and Tinnitus. Hearing loss and tinnitus are among the most common forms of disability among military veterans. The Department of Veterans Affairs (VA) reported that at the end of fiscal year 2003, disabilities of the auditory system, including tinnitus and hearing loss, were the third most common type of disability among compensated veterans. At the end of 2004, the monthly compensation payments to veterans with hearing loss as their major form of disability represented an annualized cost of some $660 million. The corresponding compensation payments to veterans with tinnitus as their major disability were close to $190 million on an annualized basis.

Washington State, workers’ compensation disability settlements for hearing-related conditions cost $4.8 million in 1991. This figure does not include medical costs or personal costs which can include approximately $1500 for a hearing aid and around $300 per year for batteries. Moreover, workers’ compensation data are an underestimate of the true frequency of occupational illness, representing only the tip of the iceberg.--  NIOSH Website

In British Columbia, in the five-year period from 1994 to 1998, the workers’ compensation board paid $18 million in permanent disability awards to 3,207 workers suffering hearing loss. An additional $36 million was paid out for hearing aids. .--  NIOSH Website

Workers’ compensation claims for hearing loss typically range from $10,000 to $25,000 per employee, but some claims have been awarded compensation as high as $150,000.  Workers in industries and jurisdictions not covered by workers’ compensation systems may bring legal action directly against the employer.

Companies that do not invest in collecting and documenting reliable data for employee exposure, hearing condition and other important decision making data run the risk of having to pay considerable costs to lawyers and noise experts when forced to challenge questionable hearing loss claims.


What Testing Options Are Available for Businesses?

Is all audiometric testing the same?  No, there are a several options that exist for business that must conduct audiometric testing for their employees.  Each business must weigh the benefits of cost, convenience, reliability and technical expertise to arrive at the best option for the business.  The most common solutions for business include:

A)   Mobile Test Vans

B)    Off-site Audiometric Testing Centers

C)    On-site Mobile Test Booth

D)   In-house Testing

From an accuracy, reliability and service standpoint, having hearing tests conducted by a qualified audiologist in an on off-site specialized clinic is the preferred option.  Unfortunately, the logistics and costs associated with transporting employees off-site make this practical for only very small firms with a handful of employees to test.  Realistically, most clinics are not set up for testing large scale firms.

Many large firms have testing facilities and personnel on-site to processes employee hearing tests.  While obviously efficient from a logistics standpoint, there may be other factors to consider.  In order to fully evaluate the cost of in house testing, there are several items to consider including the salaries of qualified testing personnel, testing equipment, upkeep, calibration and program documentation costs.

Another aspect of in-house testing that is frequently debated is impartiality “I have to wonder about the objectivity.” states Dr. Michael Stewart, Ph.D., owner of Better Hearing, Inc., an audiometric consulting firm located in Lansing, MI.  “Because the party generating the noise is also charged with monitoring the effect on employees.  It may be viewed as a conflict of interest.”  

Mobile vans are the most common testing method for most small and mid sized business.  According to Stewart “This tends to be the most economical and efficient method for testing employees in business with 200 to 500+ employees.  Usually everything can be done in one day.” 

One of the challenges for mobile test vans is addressing variability in background sound.  Because site conditions may vary from location-to-location and even year-to-year, careful attention should be given to selecting a testing site that minimizes the interference from background noise outside the test van.  Lower frequency (125 – 500 Hz) background noise is most likely to impact levels inside the van.  The test van’s construction can also account for poor audiometric test conditions due to background sound entering the booth from sources inside and outside inside the van.  


What are the Keys to Getting the Most from your Audiometric Testing Program?

1.     Qualified Personal

Having properly trained audiometric technicians, audiologist and physicians integrally involved in the process is likely the most critical factor in a quality audiometric testing program.  Some Canadian provinces require providers of audiometric tests to meet provincial qualification requirements such as British Columbia and Alberta.  In the US, OSHA does not specifically require certification (MSHA and the DOD do), although it is highly recommended that audiometric technicians be certified by the Council for Accreditation in Occupational Hearing Conservation (CAOHC).  “The worst case scenario occurs when the employee pushes the button when he or she hears the tone, but is not informed of the test results even if the results are abnormal.” says, Stewart.

Having an audiologist present during the testing, whether it is off-site, at a clinic, or on-site in mobile test vans, is critical in being able to provide immediate feedback to employees regarding their hearing.  “An audiologist can provide immediate follow-up to employees on-site and is able to identify standard threshold shifts, as well as problem audiograms”, states Stewart.  “Problems such as impacted wax and ear pathologies can be identified by audiological follow up procedures; these would not typically be addressed by technicians, as they do not fit patterns of noise-related hearing loss. An audiologist can provide consultation for employees to bring attention to these matters and also save companies money by minimizing additional follow-ups with clinics and physicians.”

2.     Quality Control for Reliable Data

A company may assume a significant liability for employee hearing loss that occurs while on the job.  Therefore, it is critical that the data driving the decision making is reliable.  It is incumbent upon the person administrating the testing for the employer to consider the reputation, the testing methodology, the analysis provided, and the quality control measures when selecting a testing firm.  This is especially critical for firms that analyze the results off-site.  Improper on-site testing could lead to wrong conclusions.  It is critical that the on-site testing people get it right. 

Many firms are focused on the efficiency (speed ) at which they can process employees through the testing.  Obviously, this has a direct impact on the costs of audiograms, but this can also can have a negative effect on the quality of the testing results.

3.     Baselines, Retests and Follow-up

Many companies are unaware of their obligation to provide hearing testing as part of a hearing conservation program.  This causes them to miss opportunities to document employee hearing ability at the beginning of their employment and therefore opening the employer to liabilities for hearing loss that may have occurred prior to employment.  On the opposite end, many companies fail to address the issue of re-tests and follow-up consultations to confirm or counter shifts found in the annual audiogram.  Much of this can be managed by ensuring that a written audiometric testing policy is developed and adhered to.

4.     Know the Applicable Regulations and Compensation Implications

Companies with sites spread over multiple jurisdictions should pay careful attention in setting audiometric testing policies, and comparing results.  The differences in determining hearing impairment and compensation can have significant financial impact on a business.  This variability may be a factor in choosing between providers capable of providing uniform service on a national/international basis or those that are more familiar with specific state/provincial regulations.

When choosing a test provider, consider the overall cost of your audiometric testing program. This may include hidden costs retests, training, and follow-up consultations not included in the hearing test.  If your provider only gives you test results, you may not be getting full value for the money you are spending. 

Mr. Cmar is President/CEO of Phase To of Canada, Inc. and also in charge of Business Development for Phase To, Inc.  Mr. Cmar has over 15 years of experience in acoustics, noise control and hearing conservation consulting.  He can be reached at (519) 734-7001 or email davecmar@phasteo.com


Mr. Dolehanty is the President of Phase To, Inc., and has over 18 years of experience in hearing conservation and noise control.  Mr. Dolehanty can be reached at (517) 886-9379 and at johndolehanty@phaseto.com.  

Dr. Michael Steward Ph.D. , is the owner of Better Hearing, Inc. and audiometric testing firm located in Lansing, Michigan.  Mr. Stewart can be reached at (517) 337-2411 or visit their website www.betterhearinghcp.com.


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