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Noise at Work
by Dr. Roy Mangubat

Noise as a Physical Hazard and The Hearing Conservation Program

Noise at Work: Noise as a Physical Hazard and The Hearing Conservation Program

By Roy Mangubat, MD, DPCOM

My Dad had work in a Sugar Mill runned by a multinational company for more than 35 years. He hears better when there is an ambient noise in the background. His work as a power plant operator exposed him to this type of hazard, being exposed to loud noisy machines led him to have some degree of NIHL or noise induce hearing loss in both ears.

Noise is a very common nuisance and now considered as a serious industrial hazard in the workplace. Not only that it can cause Noise Induced Hearing Loss (NIHL), it also ca can cause peripheral circulatory problems and cardiac diseases. Industrial Noise also adds up to a workers' STRESSOR, and stress as we all do know can cause a myriad of health problems.

Noise is measured by dosimetry and sound level meter. It is important to get the Total Weighted Average (TWA) during the entire workshift, to get the average noise exposure of the worker. Impulse noise should also be taken to ensure that the worker is not exposed to these high pressure sounds.

 Permissible Noise Exposure Limits (Taken from Book 7, Industrial Hygiene PD 856)

Threshold Limit Value for Impulse/impact Noise

*Decibels peak sound pressure level 20u Pa

Simple ways to determine the intensity of the Noise Level in the Factory

• If it is necessary to shout in order to be heard by a person within 3 feet, it is assumed that the Noise level is more than 85dB 

Environmental Control of Noise

Engineering Control

• Substitution with quitter moving parts for the machine
• Proper maintenance
• Enclosure of the noisy machinery
• Anti vibration mounting
• Use of sound absorbing materials
• Construction of soundproof control rooms

Administrative Control

• Decreasing the time of exposure by job rotations

PPE's

• Ear Muff
• Ear Plug

In establishing a hearing conservation program, it is suggested to do first an ambient noise measure (in dB at TWA) to get a glimpse of the severity of the noise/hazard. After which elements of Control must be in place to reduce the exposure to noise (engineering, administrative controls and lastly by the use of PPE's –earmuffs and earplugs). A baseline audiogram are suggested to those who are exposed, and after 6 months to a year – a repeat audiometric studies is advise, this is to determine the effectiveness of the program/intervention. Repeat Audiometric studies can also detect-  whether there is Standard Threshold Shift (STS). STS is an average of excess of 10dB for 2000, 3000 and 4000 Hz in either ear in relation to the baseline audiogram. Please be advised that there is a correction factor as for Age of an individual, this values can be seen in the AMA Guides to Permanent Impairment Evaluation.

Criteria for ENT referral (Taken from the recommendation of the American Academy of Otolaryngology (AAO)

1. Baseline Audiogram
• If there is an average loss of >25dB Hearing Threshold Level (HTL) at 500, 1000, 2000 and 3000 Hz
• If >30dB HTL at 3000, 4000 and 6000 Hz
• A difference of >15 dB HTL for 500, 1000 and 2000 Hz on both ears
2. Annual Audiogram
• >15dB change from the baseline audiogram for 500, 1000 and 2000 Hz
• >20 dB for 3000, 4000 and 6000 Hz

Typical of Noise Induced Hearing Loss

• Affects higher frequencies (3000 – 6000 Hz)
• Bilateral HL
• Symmetrical

The Effectiveness of the PPE's (earmuff and earplugs) is dependent to the worker that uses it. As also, the worth of the Audiologic studies is also dependent to OccMed Practitioner that would interpret it, since this will be the basis for interventions. I see a lot of companies that request Audiologic studies for their workers, but most of their retained physicians do not have the training to interpret audiometric readings.

Lets keep on protecting the health and safety of the Filipino Workforce!

The author is a diplomate of the Philippine College of Occupational Medicine (PCOM). PCOM is an accredited Occupational Health and Safety Organization of the Bureau of Working Conditions of the Department of Labor and Employment (DOLE), a subspecialty society under the Philippine Medical Association (PMA). PCOM is also affiliated with the International Commission on Occupational Health (ICOH) and the Asian Association of Occupational Health (AAOH).

7/22/10
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