Pile Design and Construction Practice, Fifth edition

98 Piling equipment and methods
Noise level dB(A)
120
110
100
90
80
70
Hush piling
60
5 10 15 20 25 30
Distance from source (m)
Figure 3.18 Typical noise levels for various pile-driving techniques.
Diesel hammer
Double-acting air
hammer (unsilenced)
Sound insulated
hydraulic hammer
Semi-hush piling
Under the BS Code of Practice 5228 recommendations on noise exposure levels, no person
(employee or the general public) should be exposed to a noise level of more than 85 dBA for
eight hours a day in a five-day week (now superseded by the 2005 Regulations). It is
recognized that the noise from many pile-driving methods will exceed 85 dBA but as the
operations are not continuous through the working day, the observed noise level (or ‘basic
sound power level’ as given in the Code) can be converted to an ‘equivalent continuous sound
pressure level’ that takes into account the duration of the noise emission, distance from the
source, screening and reflection. (3.6) Methods for predicting the impact of noise and the procedures
for obtaining consent from the local authority under section 61 of the Control of
Pollution Act for proposed noise control measures are detailed in BS 5228. EC3-5 does not
now include recommendations on noise and vibration levels from piling.
Local authorities are empowered under the EPA and Control of Pollution Act to set their
own standards of judging noise nuisance, and maximum day-time and night-time noise levels
of 70 and 60 dBA respectively are frequently stipulated for urban areas (and as low as
40 dBA in sensitive areas). The higher of these values can be compared with field observations
of pile-driving noise obtained from a number of sources and shown in Figure 3.18.
Tables in Part 1 of BS 5228 also provide sound level data on various piling methods. Other
information has shown that the attenuation of pile-driving impact noise to the 70 dBA level
from the noisiest of the hammers requires a distance of more than 1000 m from the sound.
Thus if a maximum sound level of 70 dBA is stipulated by a local authority, it is necessary
to adopt some means of controlling noise emission in order to protect the general public
whose dwellings or place of work are closer to the construction operations (3.7) . One method
of doing this is to enclose the hammer and pile with a sound absorbent box. The Hoesch
noise-abatement tower is formed of sandwiched steel plate/plastics construction and