Svantek SV 104BIS, Руководство пользователя

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SV 104BIS User Manual
1.1 S
OUND PRESSURE
The human ear responds to audible sound pressure levels in the
range from 20 μPa (hearing threshold) t
o
20 Pa (pain threshold), resulting in the enormous scale 1:1,000,000. Since using such a large arithmetic scale
is not practical, a logarithmic scale in decibels (dB) was introduced which is also in agreement with
physiological and psychological hearing sensations. Therefore, it is common that sound pressure is measured
in decibels. Below there is sample information about expected sound levels for different sources.
Sound source Sound level [dB]
Jet aircraft, 50 m away,
or gunshot at close range
140
Threshold of pain 130
Threshold of discomfort 120
Chainsaw, 1 m distance 110
Disco, 1 m from speaker
100
Vacuum cleaner, distance 1 m 70
Conversational speech, 1 m 60
Quiet library 40
Rustling leaves 10
Hearing threshold 0
Table 1-1 Example sound source levels
1.2 D
OSIMETRY
Noise is definitely a serious hazard in many workplaces. In case exposure to noise from machinery processes
and equipment is not correctly eliminated or controlled, it may cause permanent hearing loss in workers. The,
so called, inner ear is very fragile part of our hearing sense, which with current knowledge in medicine, cannot
be truly repaired. Therefore, it is of great importance to protect our senses from excessive noise. Exposure to
high levels of noise may also create physical and psychological stress, reduce productivity and interfere with
normal communications. This may lead to accidents and injuries by making it difficult to hear moving
equipment, other workers, and warning signals. Undoubtedly hearing loss has a very significant impact on the
quality of life for many workers and their families.
Therefore, measuring noise exposure in the workplace is fundamental part of all good hearing conservation
and noise reduction programs. The aim of taking a measurement with a noise dosimeter is to evaluate the
average exposure of employees to noise during a normal shift. Wherever the worker goes the noise dosimeter
goes too so that it captures all of the harmful noise during the typical day.
The dosimeter may be worn for the complete shift if the work pattern is so variable that it is difficult to predict
exactly what will occur or it may be worn for a shorter but representative period and then the full day’s dose
extrapolated from that sample.
1.3 S
TANDARDS
The effects of high sound exposure on hearing have been studied for many years. As far back in 1954 AIHA
(American Industrial Hygiene Association)
–
Rosenwinkel & Stewart
– described a “
new device which
integrates sound energy over finite time periods.
”
In 1956
–
von Witternand & von Gierke obtained a patent for
a
noise exposure meter for “
indicating the total time that noise exceeded a certain predetermined level
”
. Since