Pressure fluctuations sensed by the ear are known as ‘sound’. The pressure fluctuations are small changes in air pressure measured in Pascals. It is unwanted sound that is termed ‘noise’.
How do we hear and how can this be damaged by noise?
Put simply, sound (fluctuating pressure waves) enters the outer ear and into the auditory canal which creates movement of the ear drum. On the other side of the ear drum there is a mechanical amplification mechanism known as the middle ear. This system is constructed of three small bones which amplify and transmit the movements of the ear drum to the fluid filled inner ear. The movement of the fluid in the inner ear moves thousands of hair cells (which are different lengths to respond to differing frequencies of movement). The movement of the hair cells sends an electrical nerve signal to the part of the brain that decodes the information and enables us to hear.
Sustained exposure to loud noise can, over time, damage the hair cells and reduce the transmission of electrical impulses to the brain (noise induced hearing loss). It is also possible for very high pressure noise (an explosion, loud bang etc) to damage the mechanical parts of the ear e.g. the ear drum and the middle ear.
What are the signs to look out for?
Generally hearing loss is gradual. By the time it is noticed, it is probably too late. However, the following are some signs to look out for:
Conversation becomes difficult or impossible
Your family complains about the television being too loud
You have trouble using the telephone
You find it difficult to catch sounds like 't', 'd' and 's', so you confuse similar words
Permanent tinnitus (ringing, whistling, buzzing or humming in the ears) can also be caused
The aim is to prevent hearing loss before it happens.
The Control of Noise at Work Regulations 2005 came into force on 6 July 2006 and replaced the Control of Noise at Work Regulations 1989.
New exposure action values and exposure limit values have been set. The exposure action values are the levels of exposure to noise at which certain actions are required to be taken (regulations 5,6,7,9 and 10). The exposure limit values are the levels of noise above which an employee may not be exposed.
The lower exposure action values are:
a daily or weekly personal noise exposure of 80 dB(A)
a peak sound pressure of 135 dB(C)
The upper exposure action values are:
a daily or weekly personal noise exposure of 85 dB(A)
a peak sound pressure of 137 dB(C)
The exposure limit values are:
a daily or weekly personal noise exposure of 87 dB(A)
a peak sound pressure of 140 dB(C)
The use of a weekly personal noise exposure value may be used where exposure to noise varies markedly from day to day.
What does this mean to the University?
This legislation affects staff who work in noisy environments or with noisy equipment. The duties require that schools / service directorates carry out noise assessments (specialist equipment required – refer to Safety, Environment and Continuity Ext 7079) and, where exposure to noise is more than the fist action level of 80 dB(A) schools / service directorates must look at ways to:
provide information and training for employees
issue personal hearing protection
As a guide, normal conversation measures around 50 – 60 dB(A), a loud radio 65 – 75 dB(A), a chain saw 115 – 120 B(A). Note that a 10 dB(A) change in sound pressure level corresponds to an approximate halving or doubling in loudness.
Schools / service directorates where noise risk assessments already exist should review their risk assessments. Other areas, in particular where staff work in busy bar and kitchen areas, may well now come within the remit of this legislation.