Transcript Noise at Work

Noise at Work
Definitions
• Leq: Fluctuating instantaneous noise level is
averaged over a period of time. Similar to TWA.
• Lepd: Daily personal noise exposure.8 hour
equivalent continuous sound level.
• Loudness: The ears subjective judgement of
sound intensity level. Frequency is an important
factor.
• Octave Band Analysis: Used to measure the
composition of noise pressure levels and
frequencies.
dB
• Given in logarithmic form
• +3dB = doubling sound intensity so
93dB(A) for 4 hours is in fact equivalent to
90dB(A) Lepd
• Our response to sound intensity differs with
frequency, so the “A” weighted scale on
sound level meters accounts for this, hence
“dB(A)”
Problems Associated with Noise
Exposure
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Tinnitus
Noise Induced Hearing Loss
Acoustic Shock
Temporary or permanent threshold shift
Interfere with communication
Stress
Noise Measurement
• Simple sound level meters can be used
when noise level is fairly constant.
• Noise dosimeters measure Lepd where
workers are exposed to complex and
variable noise fields
Preventive Measures
• Damping (stiffening rods, double skinning
etc.)
• Absorption (absorbent materials)
• Isolation (acoustic havens)
• Enclosure (remember maintenance access)
• Reduced time exposure
• Ear protection
Types of Ear Protection
• Disposable earplugs
– Useful for temporary use e.g. visitors,
maintenance work, supervisors etc.
– Useful where employee turnover is high, whilst
ear muffs are being obtained
• Re-usable earplugs
• Earmuffs (Ear Defenders)
Earplugs Advantages
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Universal fit
Cheap
Low maintenance
Easily worn by spectacle wearers
Good user acceptance
Earplugs Disadvantages
• Low attenuation at speech frequencies
• Difficult to observe whether being worn
• Cannot be used where process involves
possibility of contamination e.g. food
• Does not reduce sound intensity transmitted
through bone structure around the ear
Earmuffs Advantages
• Provide the best attenuation across the aural
frequency spectrum
• Reduce transmission of sound intensity via
auditory canal and bones around ear
• Use is easily supervised
• Can be used where possibility of process
contamination exists e.g. food manufacure
Earmuffs Disadvantages
• Expensive
• Cumbersome – poor user acceptability
• Have to adapt to use with head protection or
RPE
• Don’t go well with long hair or glasses
• Require planning & resources to maintain
• Communication can be impaired
Control Strategy