Pile Design and Construction Practice, Fifth edition

Figure 3.19 Noise-abatement tower used for ‘Hush piling’ system.
Piling equipment and methods 99
consists of an outer 2 mm steel plate, a plastics layer 0.4 mm thick, and an inner 1.5 mm
steel plate. The plates making up the box are jointed by a rubber insertion material, and the
lid incorporates a sound-proofed air exhaust. A hinged door allows the pile and hammer to
be pitched into the tower. The Hoesch tower reduced the noise from a Delmag D12 diesel
hammer driving a sheet pile from 118 to 119 dBA at 7 m to 87 to 90 dBA at the same
distance.
A tower of similar construction is shown in Figure 3.19. Shelbourne (3.8) described the use
of the tower for driving 24 m steel H-piles by means of a 3-tonne drop hammer. Sound level
measurements of 60 to 70 dBA were recorded 15 m from the tower, compared with values
of 100 dBA before the noise-abatement system was adopted.
Surrounding only the lower part of the hammer by a shroud is not particularly effective.
A reduction of only 3 to 4 dBA was obtained by shrouding a Delmag D22 hammer in this
way. As noted in Section 3.1.4, the hydraulic hammer is a suitable type for enclosing in a
sound-proof shroud.
Crane-mounted augers using kelly bars for bored piles (see Section 3.3.4) and large CFA
rigs can produce sound power levels as high as 110 dBA, and are usually operated between
85% and 100% of the shift. This results in equivalent continuous sound pressure levels in
excess of 80 dBA at 10 m. Acoustic enclosures are essential for the engines and power
packs. The use of vibratory hammers for steel bearing piles has increased, but basic sound
levels can still be around 120 dBA and even with conversions to equivalent sound, noiseabatement
measures are necessary.