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9. It is most important to observe that the workers themselves do not receive
the main impact of the noise as the sound and percussion waves intensify as they
impinge on any high stone buildings surrounding.
10. In his enquiries he found that the men greatly preferred the mechanical
drills to the hand pick and hammer. In one. instance a body of men threatened
to strike because they were asked to go back to the methods of using human energy.
Several firms reported that with manual excavation their casualty rate increased
noticeably; chipped hands, fragments lodging in the eyes and other injuries were
not uncommon. That was the main reason for the men's preference for the mechanical
drills.
11. The use of silencers diminishes the intensity of vibration but also lessens
the efficiency of the instrument. Therefore, in order to complete certain work
within a given time it would require additional partially silenced drills for every
single unsilenced one. More men would be required and the net result would prove
of no advantage because those extra drills would cause quite as much noise as a single
unsilenced drill.
12. Dr. Crowden has studied the methods of ear stopping used among gun crews
in the Navy, and in shipyards and other industries, and showed various types with
which he had experimented. One of the most efficient and certainly the cheapest
is shown to the Committee. They ought to be distributed among those who are
about to be subjected to the noise of road drilling in their close vicinity.
13. In December, 1929, the Medical Officer of Health reported on the prevention
of noise in connection with a presentment from the Metropolitan Standing Joint
Committee. Although the matter under present consideration is limited to " rock
drills," yet it may be interesting to recall that no fewer than seven different sources
of noise were enumerated on that occasion as being causes of complaint to the
Public Health Department. He commented on the fact that the By-laws made by
the City Council from time to time to control different types of noise nuisance had
been of great public benefit; and the London County Council had also made
By-laws for other sources of noise which had also been effective.
14. Since those days other and no less obnoxious noises have arisen and some
local authorities, notably Edinburgh, have sought powers to prohibit certain noires.
There is no doubt that sooner or later public opinion will demand some measure of
relief from this growing nuisance.
Summary.
The noise caused by the use of rock drills :—
(1) Interferes with the work, occupations, or other activities of those in close
proximity to the scene of their operations.
(2) Is definitely harmful to the sick and may even jeopardise the lives of those
suffering from acute or dangerous illness.
(3) Disturbs the rest and sleep of those living nearby and is in conscquence
prejudicial to, and in some cases, injurious to health.
(4) Under existing conditions, and so far as can be ascertained at present, is
not prejudicial to the health of those operating these instruments.
(5) Usually lasts in any given locality but for a limited period say one or two
weeks and this is an important point in mitigation.