Noise is an audible sound. Noise is normally described as loud, sudden sound causing discomfort. Exposure to high noise level can harm the human ear and can even lead to permanent loss of hearing. This is why noise is a major hazard in many industries and effort is put in place to enhance industrial noise control.
Noise can cause ear damage either temporary or permanently. The different types of damages are shown below:
1. Temporary Threshold Shift – This occurs when the sensory cells in the cochlea are exposed to a short excessive noise level. This causes slight deafness, lowering sensitivity and also affecting speech. Although this is reversed when the noise is taken away.
2.  Tinnitus – This is a ringing in the ear which is caused by strong and prolonged high noise level. This ringing sensation can stay up to 24hrs after the noise has stopped.
3.  Acute acoustic trauma - This is caused by very high noise such as from an explosion. This effect can be reversible or it can permanently damage the eardrum causing permanent deafness.

Prolonged exposure to noise is highly dangerous to the health of the workers and can lead to chronic hearing effect.
This is responsible for Presbycusis- which is a hearing loss in older people which is caused by workplace noise level during their early life.

NOISE MEASUREMENT AND LIMIT
Noise is measured in the unit of decibel (dB) using a sound level meter.
There are two types of noise meter, which are:
1. The Integrated meter – These measures the average noise value for over a given period of time, which is usually 8 hours. This type of meter although more expensive are suitable for areas where the noise levels are largely unstable.
2. The direct reading meter – This type of meter gives a onetime measurement and it is okay for places where the noise level is continuous and almost at a constant value.
Noise levels are categorized into two limits which are:
3.  Exposure action value – This is the level of noise if when it is recorded then certain actions must be taken. This is usually a daily or weekly noise exposure of 80dB
4. Exposure limit value – This is the noise level above which the workers should not be exposed to. This is usually a daily or weekly noise exposure of 87dB.

NOISE CONTROL TECHNIQUES
Apart from reducing the duration of exposure to noise other techniques can be employed in industrial noise control.
These techniques are:
( a)Reduction of the noise at source
(b)Attenuation ( Reducing of the noise level received by the workers)
(c) Use of Personal Protective Equipment (PPE)

Reduction Of Noise At Source.
Noise can be reduced from source by these methods:
(a) Use another process or equipment, this may involve replacing the solid tires with rubber ones.
(b) The speed of the machine could be changed to reduce the noise level
(c) Improve the maintenance and servicing of equipment. Unlubricated parts, worn-out parts, and loose nut can increase the noise level.
(d) Relocate the work activity to a confined area where shelter can be made available
(e) Spend less time in the noisy environment.

Attenuation Of Noise Level                                                                                                                                                                                                          The noise level reaching workers can be reduced using these methods
1. Use of enclosures with sound insulating material to surround the equipment
2. Damping – This is the use of insulating floors to hamper the transmission of sound and vibration.
3.  Lagging – This is the covering of pipes and fluid containing materials to prevent heat transmission.
4.  Silencers – This is the use of absorbent or baffles on engines exhaust systems to reduce the noise.
5.  Use of a soundproof workroom to isolate workers from the noise from the operation. An example is the control room.
6. Locating the noisy equipment far away from the workforce
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