Studies of the whistles of Irrawaddy dolphins (Orcaella brevirostris) have traditionally been restricted to analyses of the human audio range (below 20 kHz). In this study, broadband acoustic recordings of Irrawaddy dolphins in Brunei Bay were obtained using a sampling frequency of 512 kHz. Among the 984 whistles collected, eight (0.81%) high‐frequency whistles were detected with fundamentals above 18.4 kHz, which is the reported maximum frequency. Four (50%) of these whistles had the entire fundamentals in the ultrasonic frequency range (above 20 kHz), where 52.3 kHz was the maximum frequency. This is the first description of the ultrasonic components of Irrawaddy dolphin whistles. Our findings demonstrate that the whistles of Irrawaddy dolphins span a wider frequency range than previously published.

中文翻译：

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文莱湾记录的伊洛瓦底海豚（Orcaella brevirostris）的高频哨声

传统上，对伊洛瓦底海豚（Orcaella brevirostris）的哨声的研究仅限于分析人类音频范围（低于20 kHz）。在这项研究中，使用512 kHz的采样频率获得了文莱湾伊洛瓦底江海豚的宽带声记录。在收集的984个口哨中，检测到8个（0.81％）高频口哨，其基波高于18.4 kHz，这是报告的最大频率。这些哨子中有四个（50％）在超声波频率范围（高于20 kHz）中具有整个基本原理，其中最大频率为52.3 kHz。这是对伊洛瓦底海豚哨声的超声波成分的首次描述。我们的发现表明，伊洛瓦底江豚的口哨声比以前公布的频率范围更广。