关键词: 长江江豚, 船舶噪声, 掩盖

Abstract: The ever-growing number of larger commercial vessels (with length and width over 15m and 5m, respectively) in the Yangtze River is becoming increasingly concerning for the conservation of the local Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis). As such, quantification of the noise emissions of these vessels is greatly in need to better understand the potential impact on the Yangtze finless porpoise. By using a broadband sound recording system, we recorded the noise emissions of a variety of large vessels at Zhenjiang region of the Yangtze River and analyzed their acoustic properties, such as peak-to-peak sound pressure level (SPLp-p) and power spectral density (PSD). The results showed that the vessel noise was featured by broadband (>100kHz) and majority of energy was concentrated in frequencies below 10kHz. The root-mean-square (RMS) sound pressure levels (SPLrms) of all frequency components were higher than 30 dB re 1μPa and raised the ambient noise levels between 3.7 and 66.5 dB across frequency bands ranging from 20Hz to 144kHz. The recorded one-third octave band sound pressure levels (TOL) for all investigated vessels were higher than 70 dB across all frequencies. The RMS levels of vessel noise were higher than the hearing thresholds of the Yangtze finless porpoise at the frequency range from 8kHz to 140kHz. These results indicate that the noise emissions from larger vessels may have negative impacts on the communication and hearing of the Yangtze finless porpoise, such as auditory masking.

Key words: Yangtze finless porpoise, Vessel noise, Masking