Sound is created when something vibrates, and moves as waves of
vibrating air molecules.
The number of vibrations per second is called frequency and is
measured in Hertz or kiloHertz.
Sound is capable of travelling tens of miles through air, at a
speed of 760 mph or 340 metres per second.
The human ear can detect sounds in the frequency range 20 Hz to
20 kHz.
Exposure to too much noise for a prolonged period of time can
cause deafness.
Noise and Deafness
Deafness can be caused instantaneously by exposure to a very high impulse.
Deafness can be caused temporarily by exposure for a period of time to high
levels of noise, typically 80 dB or above.
Continual exposure causes permanent and irreparable damage.
Noise induced hearing loss can NEVER be repaired.
Quantifying Noise
The Decibel Scale gives us a manageable way of measuring noise.
A rise in noise level of 3 dB represents doubling the noise energy.
A rise of 10 dB represents a 10 fold increase in noise energy.
Noise measurements are weighted to eliminate low and high frequency
sounds and emphasise the more damaging mid-range frequencies. This is called
`A-weighting' and is expressed as dB(A).
Sound Pressure Level (SPL) measurements fluctuate during a survey. The Leq is the
average of those measurements over a period of time.
The Leq a person receives varies during an 8 hour working day.
Lep,d is the daily noise exposure, i.e. the Leq measured over 8 hours.
Remember it is not only the level of noise which is important, but also the length of
time you are exposed to it.
Noise consists of a number of frequencies. To assess the damage potential of different
frequencies we need to analyse them.
Frequency analysis is based on internationally agreed bands of measurement.
We measure frequency in Hertz (Hz) or kiloHertz (kHz).
Mid-range frequencies are the most damaging.
The Regulations
Employers' Obligations
If you suspect that noise has reached 85 dB(A), the first action
level, an assessment should be carried out by a competent person.
If average noise is at or above 90 dB(A), or noise peaks at 140 dB,
action must be taken to reduce the noise or its effects.
You must provide ear protection to all employees exposed to between
the first and second action levels who request it. You must also
provide information about the protectors and how to obtain them.
You must provide ear protection to all workers likely to be exposed
at or above the second or peak action levels, and ensure they are used.
Areas where employees are likely to be exposed at or above the
second or peak action levels must be identified as ear protection zones.
Employees' Obligations
Wear ear protection at all times in ear protection zones.
If noise reduction methods are installed, use them properly.
Ear protection is available on request. Always wear it in accordance with the
instructions provided.
You and your employer must work together to reduce noise levels as far as is
reasonably practicable.
Ear protection
Wear suitable and effective ear protection at ALL times
when exposed to a noise hazard.
Fit your protectors BEFORE you start work.
Fit your protectors BEFORE you enter an Ear Protection Zone.
Keep protectors clean and safe when not in use.
Do not wear ear protectors that are in poor condition.