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 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 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