## 1 Introduction  
Wireless Sensor Networks (WSNs) are composed of a set of sensors with the capability to collect and transmit data in a determinate area to sense a specific phenomenon. WSNs can be applied to a great number of fields, to name a few: e-health, e-logistics, e-agriculture, etc. [1]. These networks are crucial for tracking environmental parameters, enabling early detection of changes and efficient resource management. Given this, the use of WSNs stands out as a critical technical development, providing real-time remote data collection and analysis to improve our comprehension of dynamic ecological systems and assist preventative conservation measures [2, 3, 4]. The primary goal of this study is to develop a covert communication system for signaling alerts about environmental threats to protected ecosystems, such as illegal logging and species extraction. This system transmits acoustic signals from various nodes within the network to a central base station, which decodes the messages and relays them to the designated environmental protector. It ensures regular monitoring while providing immediate alerts during unauthorized activities. Most WSNs communicate via electromagnetic signals, such as radio frequency (RF) or infrared [5], using commercial protocols like Bluetooth and IEEE802. However, attackers can disrupt RF communications to avoid detection. Therefore, using alternative communication methods, such as sound, provides an additional security layer, making the system more robust against attacks. There is a need to explore and analyze new alternatives to electromagnetic-based communication to ensure covert communications. Covert communication aims to hide the communication channel to prevent eavesdropping and jamming attacks [6, 7]. Covert communication plays a critical role in ensuring the security and reliability of sensitive data transmission. The primary significance of covert communications lies in their ability to conceal the existence of the communication itself, thereby preventing detection by unauthorized parties. This is particularly crucial in scenarios involving protecting critical infrastructure, military operations, and environmental monitoring, where the interception of communications can lead to severe consequences. One of the main challenges in covert communications is maintaining a balance between data hiding and communication efficiency. The communication system must ensure that the hidden messages are not detectable by adversaries while also guaranteeing timely and reliable data transmission. This involves sophisticated techniques to embed data within carrier signals in an imperceptible yet robust manner against various types of attacks. Another significant challenge is the potential for increased complexity and energy consumption. Covert communication systems often require additional processing to encode and decode hidden messages, which can strain the resources of sensor nodes in WSNs. Therefore, designing energy-efficient methods that minimize the impact on node performance while maintaining effective covert communication is essential. This study focuses on implementing an undetected communication system to prevent attackers from disrupting critical environmental alerts. By maintaining the element of secrecy, the system aims to provide an uninterrupted line of defense against activities that could harm the ecosystem, allowing timely responses from guardians. In this work, we focus on bird sounds as the main communication element because they have an omnipresent quality in natural environmental conditions during daylight time, and in the majority of cases, the size of the birds and their ability to fly lets them hide in their surroundings.