Noise control

Noise range	Noise levels in the environment	Effects on health
< 30 dB(A)	Rustling of leaves Whispering	None
30 - 65 dB(A)	Normal conversation Background noise in the house or office Radio and television at low volume	Negative impact on the nervous system Poor concentration Poor communication
65 - 85 dB(A)	Telephone ringing Loud speaking, loud machines Equipment, cars and lorries in city traffic	Increased blood pressure Increased risk of cardiovascular diseases Hearing damage after long exposure
85 - 120 dB(A)	Jackhammer, Motorcycle without exhaust silencer, Disco music, loud walkman music, Close to loudspeakers at pop concerts	Pain threshold Potential hearing damage even after short exposure, After longer exposure to high noise levels permanent damage to the sensory hairs in the inner ear
> 120 db(A)	Jet planes taking off Explosions	Damage to the sensory hairs in the inner ear Damage to the nerve cells in the brain Paralysis or even death

Action against the many types of noises which causes concern in buildings can be grouped into 3 main areas:

a. Source: Source of sound may be outside or within the building such as noise from

occupants.

b. Path: The sound path may be through the air from the source to the building or the path

within the building.

c. Receiver: The receiver of the sound may be the building itself or the person hearing the noise.

The following noise control can be carried out to reduce noise of the environment:

a. Design and elimination

• Noise control is most effective when it is considered at the design stage.

• Using alternative in construction methods can eliminate potentially noisy equipment and techniques.

b. Choice of equipment

• There are options at the planning stage to use quieter machinery and tools

• Example include:

1. Using a later model with improved noise insulation.

2. Using electric motors instead of petrol/diesel motors.

3. Fitting anti-vibration mountings between engines and other structures.

4. Using hydraulic system instead of pneumatic systems.

3. Work Planning

• Quieter working methods can be incorporated at the design and work planning stage.

• Example include:

1. Hydraulic piling rather than hammer piling

2. Avoiding oversized elements and therefore minimizing cutting, scrabbling and similar noise operations.

4. Work practices

• The actions of people carrying out operations have an important effect on noise control.

• Example include:

1. Correctly using equipment such as wearing their own hearing protectors.

2. Engage a skilled operator for shorter periods when using equipment of producing high noise.

5. Distance and location

• Positioning the source of noise in an isolated position for better noise control.

6. Acoustic screens and barriers

• Devices to deflect and absorb sound waves can be effective if they are placed close to the source of sound.

7. Personal protection

• If other methods fail to reduce the noise energy reaching the ear then individual hearing needs to be protected by wearing ear plugs or ear muffs (cover the entire ear).

8. Active Noise Reduction

• Using equipment that analyses a sound and speaker to produce appropriate ‘anti-noise’ which lowers the sound level.

SOUND ABSORPTION AND SOUND INSULATION

It is important to avoid confusion between sound absorption and sound insulation.