NOISE AT WORK

The only way you “adjust” or “get used” to noise is by losing your hearing.

WHAT IS NOISE? Unwanted Loud Unpleasant A matter of interpretation? sound

WHAT IS SOUND? Changes of air pressure Travels between the source and the hearer Frequency = pitch Amount of energy = amplitude

How We Interpret Sound Sound waves are collected by the outer ear Pass along auditory canal (outer ear) Ear drum oscillates in proportion with sound intensity Transmits sound waves across the bony middle ear To the oval window and cochlea (organ of hearing in the inner ear)

THE COCHLEA Spirally wound tube Filled with fluid that vibrates in sympathy with the ossicles Fluid causes stimulation of hair-like structures (cilia) Transmits electrical impulses along the auditory nerve The brain then interprets these impulses as sound

Physical Effects of Noise Excessive noise energy entering the system invokes a protection reflex, causing the flow of nerve impulses to be damped and thus causing a desensitisation to noise levels This is known as a threshold shift

THRESHOLD SHIFT Single or short duration exposure - temporary threshold shift can affect hearing ability for some hours. Repeated exposure can result in irreversible permanent threshold shift.

ACUTE EFFECTS Acute acoustic trauma - gunfire, explosions. Usually reversible, affects eardrums and ossicles Temporary threshold shift (TTS) - follows acute exposure, affects the cochlea and is reversible Tinnitus - (Ringing in the ears) results from intense auditory stimulation, usually wears off within 24 hrs

CHRONIC EFFECTS Permanent threshold shift (PTS) - prolonged exposure, affects the cochlea and is irreversible Noise induced hearing loss (NIHL) - prolonged exposure, affects ability to hear human speech, irreversible. Tinnitus - the acute form may become chronic (and constant) without warning.

HOW DO YOU KNOW THAT HEARING LOSS IS NOISE INDUCED?

AUDIOMETRY

MEASUREMENT OF NOISE Range of human hearing - from quietest detectable sound to pain threshold. A linear scale of more than 100,000,000,000 units Sound is therefore measured in a logarithmic scale - decibels

THE DECIBEL SCALE Runs from decibel(dB) Zero decibel measurement does not mean zero noise A consequence of using a logarithmic scale is that an increase of 3dB represents a doubling of the noise level.

LEGISLATION General obligations under the Health and Safety At Work Act (HSW)1974 and Management of Health and Safety at Work Regs 1992 Specific obligations under the Noise at work Regs 1989

DAILY PERSONAL NOISE EXPOSURE Generally regarded as the total exposure to noise during the day, taking into account average noise levels in working areas but not taking into account the attenuation provided by ear defenders.

ACTION LEVELS ACTION LEVELS (as defined in Reg 2) First Action Level - a daily personal noise exposure (LEPd) of 85dB(A) Second Action Level - LEPd of 90 dB(A) Third Action Level - a peak sound pressure of 200 pascals (140 dB(A)

NOISE MEASUREMENT Take into account :- Frequency (pitch) = Hz Intensity (loudness) = dB Duration (how long) = hours/mins

FIRST ACTION LEVEL (REG 8) If an individual is likely to be exposed to the first action level or above (but under the second action level) the employee must be provided, at his request - suitable and efficient personal ear defenders.

SECOND ACTION LEVEL. REG 8(2) Requires the employer to provide personal ear defenders to all workers likely to be exposed above the second or peak action level including workers with variable exposure to noise.

EAR PROTECTION ZONES (EPZ) Each ear protection zone must be demarcated and identified. No employee should enter such a zone unless they are wearing suitable ear protection

DUTIES OF EMPLOYEES DUTIES OF EMPLOYEES ( REGULATION 10.2) There is a duty on employees to co-operate with and use the measures provided by the employer under the Noise at Work Regs. It is mandatory to use ear defenders in areas that exceed the Second or Peak action levels It is mandatory to use ear defenders in EPZs

EAR DEFENDERS Ear plugs Ear muffs All have an assumed attenuation (protection) Are not all suitable for all noise levels Must be issued in accordance with the findings of a noise survey