The word ‘noise’ is one with many subjective connotations. A sound considered to be ‘noisy’ by one person may not be considered ‘noisy’ by another. Noise is essentially unwanted sound that is typically loud and disturbing in nature.
In physics, sound is simply energy that vibrates through the air in the form of a wave. The primary organ of hearing, the cochlea of the inner ear is very sensitive to these sound waves and it is the role of the cochlea to convert this acoustic information into electrochemical information so that this sound may travel to the brain for interpretation. The cochlea is lined with thousands of delicate hair cells, and when exposed to excessive noise, these delicate hair cells are damaged irreparably. Damage to these hair cells causes hearing loss.
South African health and safety guidelines stipulate that the maximum intensity (loudness) to which an individual can be exposed safely for 8 hours per day is 85dBS PL. Thereafter, with an increase of only 3dBS PL, the time is halved. In other words, a person should not be exposed to a sound of 88dBS PL for more than 4 hours, and exposure to a sound of 91dBS PL is considered safe for only 2 hours or less. To put these sound levels in perspective; the rustling of leaves creates a sound of about 20dBH L, while general conversation occurs at a loudness of approximately 60dBH L. A vacuum-cleaner or lawn-mower generate noise of 70 to 80dBH L and live rock music is typically played at approximately 110dBH L!
Hearing protection devices (HPDs) are very effective in reducing the amount of sound entering the ear and thus reaching and potentially damaging the delicate cochlea. HPDs are available in different shapes and sizes and the efficacy of these devices is quite varied. The most readily available HPDs are foam ear plugs which can be bought from most pharmacies. Foam ear plugs are not as effective as silicone/ acrylic custom-made ear plugs; which are made to fit your ear canals specifically for improved comfort and noise protection. For maximum protection (e.g.: when using a firearm), ear muffs (which are placed over the ears), paired with custom-made ear plugs are recommended.
An audiologist takes an impression (measures the shape) of your ear so that custom made ear plugs can be made.