Noise

OCCUPATIONAL NOISE

About 70% of all workers compensation claims relate to hearing loss at work, and the cost to employees and employers is high.

In NSW the legislation requiring employers to prevent employee exposure to excessive noise is the Occupational Health and Safety Regulation 2001 (sec 49), under the Occupational Health and Safety Act 2000. The Act requires every employer to ensure the workplace is safe. The Regulation defines a workplace as unsafe if any person is exposed to noise levels that exceed an 8 hour noise equivalent of 85dB(A) or that peak at more than 140dB(C).

The Regulation is concerned only with noise levels which may result in hearing loss. Noise levels well within the limits set by the Regulation can cause discomfort, annoyance and loss of productivity especially in an office environment.

Noise is measured on a logarithmic scale of decibels. The noise scale across various frequencies is linear, however the human ear does not hear all frequencies, hence measurements are usually made on an A weighted scale (dB(A)).

Australian Standard AS/NZS 1269.0-3:1998 provides an overview of noise measurement, management and hearing protection. The hearing protection program now applies to various classes of Hearing Protectors such as ear plugs and ear muffs, however many manufacturers still use the old SLC rating.

New Environment can measure noise exposure levels and assess the risk. We can advise on selection of hearing protection, noise management policies and preparation of noise control plans and strategies.

ENVIRONMENT AND CONSTRUCTION NOISE

While Occupational Noise is concerned with preventing hearing damage, Environmental Noise is concerned with preventing discomfort and nuisance noise outside the site.

The characteristics of a sound which affect human response include:

• How loud it is. The ear responds to a range of sound intensities and it responds differently at various levels of intensity.
• The frequency or tone. The ear is more sensitive to higher frequencies in the hearing range (except at very high sound levels where tones of all frequencies seem to have a similar loudness).
• Background noise.
• Characteristics such as pulse.
• The time and place, stress and social factors, and information content.

Sound is measured as the Sound Power Level (Lp) which is ten times the log to the base 10 of the power relative to a reference power level. The scale for Sound Power is decibels dB. To adjust for the ear's frequency response an A weighted scale is used, dB(A).

The accumulated exposure over a given period T is written as Leq,T or LAeq,T. As a rough rule, for every extra 10dB(A) the sound seems twice as loud.

For Environmental Noise the figures L10 and L90 are often used. These are the A weighted levels exceeded for 10% and 90% of the measurement period. L90 usually constitutes the background level if measured before construction begins.

The allowable exceedance over background depends on a number of factors. Lower exceedances over background apply if the noise is pulsed or of a narrow frequency band. Working hours restrictions also apply.

New Environment can assist in Noise measurement, advice and consultancy.