Hearing loss due to industrial noise is one of the most widespread yet preventable work place injuries. Continual exposure to noise from machinery, tools, traffic and general workplace activity can cause significant, irreversible hearing loss.
Hearing loss has a dramatic impact on quality of life and may contribute to other safety problems, such as lack of awareness and reduced concentration. Correctly designed and fitted ear protection will keep industrial noise below harmful levels.The choice of the appropriate protection device for each job is also vitally important.
When does noise become harmful to your hearing?
Exposure to sounds greater than 85 dB may cause hearing loss. General estimates of some work-related noises are listed in the chart below.
This table is a general guide only and is not an absolute basis for noise levels selection as some equipment may operate at different noise levels. Every worksite should be tested by OH&S.
How do I choose my hearing protection?
The choice of hearing protection depends on a number of factors including level of noise, comfort, and the suitability of the hearing protection for both the worker and the environment. Most importantly, the hearing protection should provide the desired noise reduction.
It is best where protection must be used, to provide a choice of a number of different types of hearing protection. Each hearing protection device is given a class rating from 1 to 5 to show the level of noise reduction achieved.
If the noise exposure is intermittent, ear muffs are more desirable, since it may be inconvenient to remove and reinsert earplugs.
How is hearing protection tested in Australia and New Zealand and what standards apply?
The Sound Level Conversion (SLC80) rating as applied to hearing protection devices (HPD) is a simple number and class rating derived from a test procedure outlined in the Australian/New Zealand Standard, AS/NZS 1270: 2002. It provides a simple number guide to the level of noise attenuation (reduction) that can be expected from a particular HPD.
Because humans are different, the level of protection achieved for each person could also be different and so a scientific formula is used to allow for differences. The SLC value includes a correction to ensure that the stated degree of noise reduction is obtained on 80% of occasions. Hence the SLC80 rating. The SLC rating is the difference between the sound leve1 0 of the environment in which the HPD is worn and the sound level reaching the wearer's ears. The testing procedure can be separated into two different areas:
1) Mechanical Testing:
Where the device is subjected to physical forces, stretching, heating and concussion - to simulate real wearing conditions over a period of time.
2) Audiometric Testing:
This is a subjective test. A minimum number of human test subjects are selected at random and given a hearing test to establish if they fall into the category of "normal hearing", as outlined in the standard. The attenuation of the HPD is determined by measuring each subject's hearing threshold with and without the HPD fitted. The difference between these two thresholds is the so called real ear attenuation of the HPD to a variety of frequencies.
In simplistic terms, from this data the mean real ear attenuation and standard deviation (variation) at each frequency is calculated. The mean minus standard deviation, when subtracted from the band level gives the attenuation. HPD are also given a class rating, as outlined below, once the SLC80 rating is known, and refers to the level of noise attenuation achieved by each device. The higher the rating, the greater the efficiency of the hearing protection device.
The SLC80 is a rating only, by which in conjunction with the information contained in the Australian/New Zealand Standard AS/NZS 1269.3:2005 Occupational Noise Management - Hearing Protector, the problems of hearing loss due to noise exposure for a given environment are addressed.
Source: ProChoice Hearing Protection Standards found on Page 118 of our Pro-Pac Packaging Product Catalogue 2018/19.