Hearing Loss in Production EnvironmentIntroduction

When hearing loss occurs caused by noisy work environment, a person might just be ended up with a hearing aid with compensation. However, is this the real cost that incurred? It is highlight here to suggest strategies that are applicable in today’s competitive environment that will resolve the problem, whether immediate or in the near foreseen future.

Noise Regulation

Factories and Machinery Act 1967, Noise Exposure Regulation 1989 states that the allowable noise limit is 85dB(A) for 16 hours duration and not exceeding 115dB(A) at any time. This law is applicable to protect hearing among personnel working near the equipment. The impact on human ears caused by machinery emission is severe as it is of a non-recovery pattern when damaged. This legal enforceable Act in Malaysia is strictly obeyed as it is mandatory to measure the baseline reading.

The Derivation of the Decibel (dB) Unit

It is important to know the constituents that make up the decibel dB unit. It is merely represented by the formula below.

Sound Pressure Level, SPL = 20 log10 (p/po) [dB]

Where p is the pressure caused by the machinery

Po is the reference sound pressure

It is referred to as dBA or dB(A), due to the A-weighting filter. applies to the instrument measuring the sound level.

Impact on Human Ears

The constant noise level of unwanted sound weakens our hearing ability. This causes the

ears to have difficulty in listening to normal noise level than before after continuous exposure. Among the group, some might be susceptible to the noise level. However the shift in threshold from the baseline measurement is evidence of the damage.

Noise Emission from Production Machine

Propagation of pressure wave excites the air creating loud audible noise within measurable frequency. The noise level measured by noise meters and are mapped to shows the distance of decibel dB level from the machine. Thus this alert the inhabitants of the limiting distance.

Susceptibility of Individual to Noise Exposure

This is unavoidable as it depends on individual. Thus the mechanism to detect this is a threshold shift from baseline measurement or a consultant advice on the person’s situation. Noise exposure measurement using dosimeter is available to check individual exposure level.

Strategies Preventing Hearing Loss Among Personnel

There are three strategic methods to limit the noise level to acceptable level

(1) limit the sound energy from entering the ears of personnel – personnel are located in the control room and monitor the plant performance in there. Noise will not enter into this area. Ear muffles also help to reduce the noise level entering the ears.

(2) enclose the noise to prevent the noise from escaping to the surrounding – by enclosing the noise source, the propagation of sound wave will not escape.

(3) eliminate the noise source – engineering measure to specific equipment in order meet the allowable level by law, e.g. control valve with anti-cavitation trim to avoid formation of cavities downstream of the pipeline eliminating noise totally

Administrative Control

Signboards to warn personnel that the designated high noise area are restricted. Should personnel has to enter these areas, they shall be equipped with proper ear muffle.

Conclusion

The impact on ear due to production noise is of a non-return pattern. Hearing loss due to production noise is common if the law is not practised. Select the appropriate strategy to resolve the problem(s).