Underwater sounds near a fuel receiving facility in western Hong Kong: relevance to dolphins

TitleUnderwater sounds near a fuel receiving facility in western Hong Kong: relevance to dolphins
Publication TypeJournal Article
Year of Publication2002
AuthorsWürsig, B., and
JournalMarine Environmental Research
EndNote Rec Number2860
KeywordsNoise effects on Marine Mammals

Western Hong Kong is home to two species of marine mammals: Indo-Pacific humpbacked
dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides). Both are threatened
in many parts of their range in southeast Asia [for example, International Biological
Research Institute Reports 9 (1997), 41; Asian Marine Biology 14 (1997) 111]. In 1998, when
the new Hong Kong International Airport opened in western Hong Kong, small tankers
(about 100 m long, cargo capacity about 6300 metric tons) began delivering fuel to the Aviation
Fuel Receiving Facility (AFRF) just off Sha Chau Island, north of the airport. Calibrated
sound recordings were taken over a 4-day period from a quiet, anchored boat at distances 80–
2000 m from aviation fuel delivery activities at the AFRF. From the recordings, 143 sections
were selected for analysis. Narrowband spectral densities on the sound pressures were computed,
and one-third octave band levels were derived for center frequencies from 10 to 16,000
Hz. Broadband levels, viz. 10–20,000 Hz, were also computed. The results showed that the
Sha Chau area is normally noisy underwater, with the lowest broadband levels measured
corresponding to those expected during a storm at sea (sea state 6). This background noise is
believed to come largely from heavy vessel traffic in the Urmston Road to the north and east
of Sha Chau and from vessels in the Pearl River Estuary to the West. The sound levels from
the AFRF tankers are comparable to the levels measured from similar- and smaller-sized
supply vessels supporting offshore oil exploration. The strongest sounds recorded were from a
tanker leaving the AFRF at distance 100 m from the hydrophone, for which the one-third
octave band level at 100 Hz was 141 dB re 1 mPa (spectrum level 127 dB re 1 mPa2/Hz) and the
10–20,000 Hz broadband level was 146 dB. At distances of 100 m or more and frequencies
above 300 Hz, the one-third octave band levels were less than 130 dB (spectrum level 111 dB.