Audiometry - PTA

Pure-tone audiometry is a behavioral test used to measure hearing sensitivity. This measure involves the peripheral and central auditory systems. Pure-tone thresholds (PTTs)

indicate the softest sound audible to an individual at least 50% of the time. Hearing sensitivity is plotted on an audiogram, which is a graph displaying intensity as a function of frequency.

 A baseline audiogram is obtained before the worker is exposed to potentially

hazardous noise, periodically during the exposure times.

It is good practice to obtain an audiogram for those workers leaving a place or position with exposure to hazardous noise, whether because of transfer, cessation of employment, or retirement.

The audiogram will provide the best estimate of the worker’s hearing at the termination of exposure to workplace noise for this employment situation.

The exit audiogram has more value for the employer than the employee, because it specifies

the amount of hearing loss incurred while employed in this situation.(NIOSH 1995)

PTA is used to assess the Auditory fitness for duty (AFFD). AFFD refers to the possession of hearing abilities sufficient for safe and effective job performance. In jobs such as law enforcement and piloting, where the ability to hear is critical to job performance and safety, hearing loss can decrease performance, even to the point of being hazardous to self and others. Tests of AFFD should provide an employer with a valid assessment of an employee’s ability to perform the job safely, without discriminating against the employee purely on the basis of hearing loss.

(Tufts J, 2009)

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for hearing loss in asymptomatic adults aged 50 years or older. (USPSTF 2014 )

·         International standards:

1. The hearing threshold shall be determined by pure tone audiometry (PTA).in relation to a zero value on the dB scale, without adjustment in relation to the normal hearing threshold for age or use of a hearing aid.Guidelines - health requirements for persons working on installations offshore. (Norwegian Directorate of Health 2012)
2.  
3. The hearing loss shall be calculated as an absolute value

1. Offshore medical, Audio metry is required, The hearing threshold shall be determined by pure tone audiometry (PTA). (Norwegian Directorate of Health 2012)

-      Offshore medical, Audiometry is a routine test required for fitness assessment.

 (UK Offshore Oil and Gas 2008)

-      Offshore medical, Audiometry is required (meeting OSHA guidelines).

(GoM BP 2012)

1. Fire fighters; Baseline audiometry isperformed in accordance with 29 CFR 1910.95, All audiograms should be done with no exposure to industrial noise for 14 hours.
2. (NFPA 2012)

-      Divers audiometry is a routine test.

(HSE UK, MA1, 2011)

1. Hazardous occupations; Workers whose daily personal noise exposure is 85 dB(A) or above.
2. Pre-employment (within 4 months before commencing employment), once ever 24 months for daily personal noise exposure between 85 and 89 dB(A) and once every 12 months for daily personal noise exposure of 90 dB(A) and above(Hong Kong 2004).

-      The employer must administer a continuing, effective hearing conservation program whenever employee noise exposures are at or above an eight hour time-weighted average (TWA) of 85 dBA or, equivalently, a dose of 50 percent. The employer must retain all employee audiometric test records.

(OSHA, 2009).

-      Commercial drivers; drivers of commercial vehicles are required to meet a hearing standard. Compliance with the standard should be clinically assessed initially. If there is doubt about the person’s hearing, audiometry should be arranged (Austroads 2012).

·         Suggested indications: PTA is required for employees in operation area expected to expose to workplace noise, offshore, divers fire fighters and safety critical positions.

References

1.       NIOSH, Hearing Measurement, Franks, J R. 1995,

2.       From:http://www.who.int/occupational_health/publications/noise8.pdf

3.       Tufts J, (2009) Auditory Fitness for Duty: A Review (DOI: 10.3766/jaaa.20.9.3) from: http://www.audiology.org/sites/default/files/journal/JAAA_20_09_02.pdf

1. Kronick, R. (2014). The Guide to Clinical Preventive Services. USPSTF. Retrieved from http://www.ahrq.gov/professionals/clinicians-providers/guidelines-recommendations/guide/cpsguide.pdf
2. Guidelines - health requirements for persons working on installations offshore. Norwegian Directorate of Health 2012.
3. Medical Aspects of Fitness for Work Offshore ( 2008 The United Kingdom Offshore Oil and Gas)
4. GoM Medical Aspects of Fitness for Offshore Work Safety Work Practice (BP 2012)
5. NFPA 1582, Chapter 6 Medical Evaluations of Candidates - 2012
6. HSE UK, The medical examination and assessment of divers (MA1) 2011, http://www.hse.gov.uk/Diving/ma1.pdf
7. Doctors’ Guide to Medical Examinations for Workers engaged in Hazardous Occupations in Industrial Undertakings - Occupational Safety and Health – 2004, Hong Kong.
8. OSHA, Screening and Surveillance: A Guide to OSHA Standards, 2009 https://www.osha.gov/Publications/osha3162.pdf
9. Austroads (2012) ASSESSING FITNESS TO DRIVE, for commercial and private vehicle drivers, ISBN: 978-1-921991-86-8