###### Abstract
researched the acoustic signals of the _White porpoise_ (_Delphinapterus leucas_) by a hydrophone working at 0.5 kHz-10 kHz in 1949 [21]. Since then, many researchers have used hydrophones to study the characteristics of the acoustic signals of _Cetaceans_. In 1993, [PERSON] summarized the results of acoustic research on a variety of _Cetaceans_ and compiled a book entitled The Sonar of Dolphins [3]. After determining the characteristics of _Cetacanus_' acoustic signals, researchers began to study the relationship between _Cetacanus_' acoustic signals, environment, and behaviors based on these characteristics. Therefore, the detection and analysis of acoustics became increasingly important. _Tursiops truncatus_ are known to avoid obstacles in their paths while swimming and to locate fishes for food by sound reflection or by echolocation [4; 22]. [PERSON] et al. found that the upper limit of hearing of _Tursiops truncatus_ can reach 120-140 kHz. [PERSON] et al. studied the high-frequency echolocation signals of _Sousa chinensis_ in Sanniang Bay, Guangxi Province, China, and found that the mean peak frequency was 109 kHz [18]. [PERSON] et al. researched the echolocation signals of captive and free-ranging _Neophocaena asineorientalis_ and found that the main center frequency of clicks from individuals in the Baiji aquarium was 133 kHz, while that of individuals at the Shishou Tian-e-zhou Reserve was 128 kHz, and that of individuals at Tianxingzhou was 129 kHz [23]. In most studies, the researchers released the hydrophone into the water to collect acoustic signals. Some pressed the hydrophone against the skin of dolphins, as in [PERSON] et al. 's research [24]. _Cetacean_ acoustic signals can be separated into whistle, burst-pulse, and click signals based on their time-frequency characteristics. The click signal is a broadband signal with an upper limit of frequency up to 150 kHz, with some reaching even more than 200 kHz. It is still difficult to identify the click signals of _Odontocet_ in large quantities for research purposes. On the one hand, marine environment noise leads to some interference with the sound signals. On the other hand, knocks and sounds of non-target marine animals may be misidentified [25]. [PERSON] et al. designed an FChOA-MLPNN for the automatic detection of marine mammal sounds [26]. However, the manual labeling of the dataset consumed a great deal of labor and could lead to the mislabeling of knock signals as click signals. [PERSON] et al. transformed hydrophone data from the time domain into the time-frequency domain using a short-time Fourier transform (STFT). The acoustic signals of dolphins can be marked according to their duration, short energy, and spectral centroid. Due to the uncertainty principle, the time-frequency spectrum calculated using STFT cannot maintain a high temporal resolution and high-frequency resolution at the same time. [PERSON]'s method can mark whistle and burst pulses accurately, but there are some mismarks of clicks [27]. Since the development of the digital signal processing (DSP) method, a new signal analysis method has been produced, i.e., the wavelet transform (WT), where the resolution can be dynamically changed in accordance with the frequency. Although WT still cannot ensure both a high temporal resolution and high-frequency resolution in a window at the same time based on the uncertainty principle, the dynamic resolution captures greater details of wide-frequency band signals [28]. Thus far, WT has been applied to seismic signal recognition, part flaw detection, image processing, and other fields [29; 30; 31]. In this research, we studied the usage of WT for _Cetacean_ acoustic signal detection; recognized whistle, burst-pulse, and click signals with WT; and compared these data with the results obtained using traditional STFT and manual methods. This research lays the groundwork for the detection of many _Cetaceans_' acoustic signals and can support species protection efforts and the study of _Cetaceans_' habits.