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

摘要： 长江航运业的快速发展导致长江中船舶数量激增，相应的水体噪声污染可能对同水域的长江江豚（Neophocaena asiaeorientalis asiaeorientalis）产生一定的负面影响，本研究采用宽频录音设备对长江和畅洲北汊非正式通航江段的各类常见大型船舶（长>15m且宽>5m）的航行噪声进行了记录，并分析其峰值-峰值声压级强度（SPLp-p）和功率谱密度（PSD）等。结果表明，大型船舶的航行噪声能量分布频率范围较广（>100kHz），但主要集中于中低频（<10kHz）部分，各频率（20Hz~144kHz）处的均方根声压级（SPLrms）对环境背景噪声在该频率处的噪声增量范围为3.7~66.5dB。接收到的1/3倍频程声压级（TOL）在各频率处都大于70dB，在8~140kHz频段内都高于长江江豚的听觉阈值。说明大型船舶的航行噪声可能会对长江江豚个体间的声通讯及听觉带来不利影响，如听觉掩盖。

关键词: 长江江豚, 船舶噪声, 掩盖