The suppression of noise does not seem to be high on the agenda of modern industrial machinery designers. Unfortunately, worker victims of the noise find it all too easy to suffer easily-perceptible permanent hearing loss as a consequence. That is, irreversible damage can occur without the victim being aware of it. Dangerous noise can be sudden or prolonged. We have all found ourselves temporarily deafened by noise. Human hearing can deal with many such instances, if they are infrequent. Admittedly, some noises are so extreme that a single instance will cause permanent damage. While this is not the typical cause of hearing loss claims *, due to the way the ear functions, sudden or intermittent noises can be more harmful than continuous noise.
The functional range of human hearing is very wide, ranging from frequencies of 20Hz to 18,000 Hz. The human ear is most suited to hearing in the range of 500 Hz to 4,000 Hz. Human speech occurs in the range 500Hz to 2,000 Hz.
The measurement scale of “decibels” is a measure of pressure induced on the ear by sounds. The usual scale referred to is the “A” weighted scale expressed as dB(A). This scale measures the pressure exerted on the human ear by sound. It is, in effect, measuring the energy applied to the ear by sound.
It is a logarithm scale; each level is 10 times more intense than the previous level. Put another way, the difference between 40 dB(A) and 43 dB(A) is a doubling of the sound level, not an increase of 3 increments.
That sound is energy is more easily understood in the context of “intrasound”, sound below the level of human hearing – felt as vibration.
The U.K. Code of Practice for Reducing the Exposure of Persons to Noise (1976) set out the following maxima for duration of exposure.
dB(A) Max. duration
90dB(A) 8 Hours
93dB(A) 4 Hours
96dB(A) 1 Hour
99dB(A) 30 Minutes
102dB(A) 15 Minutes
105dB(A) 7 Minutes
108dB(A) 4 Minutes
111dB(A) 2 Minutes
114dB(A) 1 Minute
120dB(A) 30 Seconds
For the current position in the UK see HERE.
See HERE for the Employer’s duties.
The effect of “loud” noises on the ear is lower at low frequencies than at the higher frequencies. Noise induced damage takes place initially above the range of normal human speech. Difficulty in hearing speech means that very considerable hearing loss has already taken place. This damage first manifests itself as reduced ability to hear frequencies about 2,000 Hz, the upper range of human speech. As a rough guide to dangerous noise, if a worker needs to shout to be heard properly at a distance of 3 feet, the noise in the environment is too loud. Needless to say, this is not an acceptable method of measuring noise and measurement should be done with the proper equipment. This equipment comes in a range of measuring devices including sound level meters and personal “dosimeters”.
Hearing loss is not the sole result of noise. It can cause accidents due to misunderstandings: it can produce variations in heart-rate, blood pressure, respiration, dilation of pupils and changes in the blood. It can lead to peptic ulcers due to gastrointestinal disturbance.
In addition, if hearing loss is suffered, the victim is required to make a constant effort to compensate and this leads to stress, either in maintaining the effort, or through personal clashes when the effort cannot be sustained and family feelings are hurt. Stress can also be suffered through a permanent buzzing or whistling in the ears in the case of hearing damage. Hearing loss claims * can only provide monetary compensation. They cannot put the injured person back in the state before injury. This is why prevention of injury is by far the most preferable path.
The solution to dangerous noise is to eliminate the noise or reduce it. This may be done by designing machinery to work quietly; buying a machine of different design; enclosing the machine in noise insulation material; providing the worker with effective ear protection.
Many ear protectors are not comfortable and are not really fit for their purpose. Proper thought must be given to the provision of such protectors. They are a last resort and can be justified only if all other methods of dealing with the problem have been considered and are impracticable.
Sound Levels of Some Noises
- Carrier deck Jet 140
- Oxygen torch 126
- Pneumatic chipper 122
- Pavement Breaker 115
- Textile Loom 112
- Jet overflying at 300m 110
- Excavator 110
- Grinding of metal 108
- Cut-off saw 106
- Farm tractor 103
- Petrol Lawn mower 103
- Chain saw 102
- Newspaper Press 101
- Excavation rock drill at 15 m 100
- Petrol lawn mower 96
- Motorcycle at 8m 96
- Lathe 95
- Heavy truck at 15m 93
- Food Blender 90
- Milling Machine 90
- Train Whistle at 150 m 90
- Alarm clock 85
- Clothes washer 82
- Domestic food blender 81
- Car at 100 km/h at 15 m 76
- Inside average house 50
- Quiet conversation 40
- Ticking watch 30
The following is a list of occupations or workplaces showing the typical noise levels found in them:
INDUSTRY PERMITTED EXPOSURE
130 dB or more
Jet engine testing { DO NOT ENTER AREA
Riveting a large steel structure { DO NOT ENTER AREA
120-129 dB
Chipping a large steel casting {Hearing Protection
Riveting a small steel structure {Hearing Protection
Working a chain saw {Hearing Protection
110-119 dB
Steel mills {Hearing Protection
Metalworking {Hearing Protection
Engine testing {Hearing Protection
100-109 dB
Mining { 7 Min to 1 Hour Max Exp
Drilling { 7 Min to 1 Hour Max Exp
Sawing metal or bone { 7 Min to 1 Hour Max Exp
Machine Woodworking { 7 Min to 1 Hour Max Exp
Heavy excavation { 7 Min to 1 Hour Max Exp
Grinding { 7 Min to 1 Hour Max Exp
Paper Manufacturing { 7 Min to 1 Hour Max Exp
Newspaper and Book Printing { 7 Min to 1 Hour Max Exp
Boiler rooms { 7 Min to 1 Hour Max Exp
Plastic moulding { 7 Min to 1 Hour Max Exp
Food Mixing { 7 Min to 1 Hour Max Exp
Crushing stone { 7 Min to 1 Hour Max Exp
90-99 dB
Canning {1 Hour to 8 Hr. Max Exp
Textiles {1 Hour to 8 Hr. Max Exp
Small scale Printing {1 Hour to 8 Hr. Max Exp
Leatherworking {1 Hour to 8 Hr. Max Exp
Welding {1 Hour to 8 Hr. Max Exp
Working farm machinery {1 Hour to 8 Hr. Max Exp
Assembling machinery on a line{1 Hour to 8 Hr. Max Exp
80-89 dB
Clothing manufacturing { Deemed unsafe in Holland
Warehousing { Deemed unsafe in Holland
In every industry shown above the employer is obliged by law to provide personal hearing protectors for the workers,, assuming that the daily exposure is in excess of 85 dB(A).
It can be seen that substantial areas of industry represent a danger to the hearing of the persons employed in them. There is serious disagreement on the proposition that exposure to 90 dB (A) for an 8 hour day is a “safe level of exposure”. This can be seen in the view in Holland that 8 hours of exposure to noise of 80 dB(A) or more is unsafe. If precautions in the form of noise shielding or personal protection are not taken, it is inevitable that hearing loss in the working population in industry will be considerable by the time they retire. It has been estimated that the future liability of British Coal for claims for deafness will reach £415,000,000.
The remedies for excessive noise are (in order of descending preference);
a) design quiet machinery;
b) buy quiet machinery (make the supplier state the noise levels produced by the machine especially at the operator’s position);
c) enclose noisy machinery;
d) put noisy machinery in a separate room;
e) fit silencers on exhausts;
f) ensure workers wear ear protectors;
g) reduce noise exposure of workers by rest and rotation;
The “recommended dose” of 90 dB(A) for an eight hour day without ear protectors is an approximation. It does not take into account individual sensitivity. It does not mean that hearing damage cannot occur from such exposure. The dose is achieved by averaging exposure over an eight hour day. Needless to say, this presupposes that the noise levels in the workplace and variations between one part and another are accurately known.
As can be seen from the detailed nature of the above, hearing loss claims * arising from exposure to loud noise in a work environment will benefit from expert advice. If you want to contact a solicitor about assessing your situation, you can reach us us via our Online Contact Form or by calling 01-6351580. It is difficult to assess compensation levels in hearing loss claims * as the PIAB Injuries Board Book of Quantum does not give estimates of ranges of awards, as it does for other forms of injury.