Measurements of underwater conductor hammering noise: compliance with the German UBA limit and relevance to the harbour porpoise (Phocoena phocoena)
Invited paper
Southampton Solent University
Tuesday 2 june, 2015, 13:40 - 14:00
0.8 Rome (118)
Abstract:
Cetaceans (whales, dolphins and porpoises) rely heavily on sound for
communication, foraging, predator avoidance, orientation, and navigation.
Noise
generated by offshore construction work, such as piling during wind-farm
construction and conductor hammering during exploration-drilling operations,
has
the potential to cause behavioural changes, masking of communication signals
or,
in extreme cases, a temporary loss of hearing in marine mammals. Numerous
countries have issued individual standards for offshore noise monitoring
before,
during and after construction, but few standards specify actual noise
thresholds, due to the complexity of underwater environments. Underwater
noise
measurements were taken from an offshore support vessel, stationed at
distances
of 750 m, 1 km, and 2 km away from a drilling-rig conductor hammering site
in
the North Sea. Results were then compared with the only official threshold
value, which was issued by the German Federal Environment Agency (UBA).
Sound
Pressure Level (SPL) at various measurement locations, and beyond was
predicted.
The Sound Exposure Level for conductor hammering noise was monitored in real
time, and did not reach 160 dB re 1 µPa at a distance of 750 m, in
accordance
with the UBA. Given the known behaviour of porpoises around offshore
installations, it is unlikely that animals were exposed to levels of sound
that
might be potentially detrimental in the single and brief 2 h period that
conductor hammering occurred.