###### Abstract  
_Cetacanus_ are an important part of the ocean ecosystem and are widely distributed in seas across the world. _Cetacanus_ are heavily reliant on acoustic signals for communication. Some _Odontocet_ can perceive their environments using their sonar system, including the detection, localization, discrimination, and recognition of objects. Acoustic signals are one of the most commonly used types of data for _Cetacam_ research, and it is necessary to develop _Cetacam_ acoustic signal detection methods. This study compared the performance of a manual method, short-time Fourier transform (STFT), and wavelet transform (WT) in _Cetacam_ acoustic signal detection. The results showed that WT performs better in click detection. According to this research, we propose using STFT for whistle and burst-pulse marking and WT for click marking in dataset building. This research will be helpful in facilitating research on the habits and behaviors of groups and individuals, thus providing information to develop methods for protecting species and developing biological resources. W acronyms: _Cetacam_: 2023, 13, 4521. [[https://doi.org/10.3390/app13074521](https://doi.org/10.3390/app13074521)]([https://doi.org/10.3390/app13074521](https://doi.org/10.3390/app13074521))  
**Citation:** [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]. Application of Wavelet Transform for the Detection of Cetacean Acoustic Signals. _Appl. Sci._**2023**, _13_, 4521. [[https://doi.org/10.3390/app13074521](https://doi.org/10.3390/app13074521)]([https://doi.org/10.3390/app13074521](https://doi.org/10.3390/app13074521))  
Received: 21 January 2023  
Received: 22 March 2023  
Accepted: 28 March 2023  
Published: 2 April 2023  
**1. Introduction**_Cetacanus_ belong to _Whippomorpha_, including _Mysticeti_ and _Odontocet_. Acoustic signals are the most important way in which _Cetacanus_ perceive their environment and communicate, especially active acoustic signals generated by _Cetacanus_[1, 2]. _Odontocet_ can use their sonar systems for echolocation through wide-frequency band signals [3, 4]. Since the 20 th century, due to excessive whaling, these animals' habitats have been reduced in size, and some species are now endangered [5, 6, 7, 8]. To protect _Cetacanus_, the International Whaling Commission (IWC) devised the International Convention for the Regulation of Whaling [9]. In recent years, studies have shown that in addition to human hunting, the noise generated by human activities also has a greatly negative impact on _Cetacanus_[1, 10, 11, 12, 13, 14, 15]. _Odontocet_, especially _Delphinidae_ and _Phocaeridae_, are highly dependent on their sonar systems for environmental perception and predation [16, 17, 1, 3, 2]. Human activities are frequent in rivers, estuaries, and coastal areas, and the noise produced results in serious interference with, and even damage to the auditory systems of _Odontocet_[10, 11, 12, 13, 15]. Taking _Sousa chinensis_ as an example, we can observe that their click signal is a broadband signal with a short duration [18], which is easily masked by impact or knocking noises [13]. Young individuals can distinguish artificial knocking sounds and click signals from their own. However, the hearing capacity of elder individuals gradually becomes worse with increased age [19; 20], resulting in the confusion of knocking sounds and clicking signals and causing them to enter rivers by mistake. Some aged _Sousa chinensis_ have been killed due to grounding or fungal infection based on these mistakes. The study of _Cetaceans_' acoustic signals is important for species protection measures and biological resource development. Hydrophone data are the most widely used type of information in _Cetacean_ research because sound travels much further than light in water and is more easily recorded. The acoustic research on hydrophone data of _Cetaceans_ began in the 1940s, given that hydrophone technology was developed in World War II. [PERSON] et al.