## 4 Network Description  
The system comprises \(N\) nodes distributed in the region of interest to detect certain events. These nodes transmit data packets regarding the environmental conditions (movement, presence of people, etc.) to a sink node in a single hop using the Slotted ALOHA  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Audio Name** & **Duration of Audio** & **Coefficients Modified** & **\% Modified** & **bps** \\ \hline XC3989 Cuitlacoche & 10 s & 644 & 1 & 2060 \\ XC196554 Cuitlacoche & 13 s & 1617 & 2 & 3980 \\ XC5127 Scolitario & 36 s & 2190 & 1 & 1946 \\ XC5145 Solitario & 28 s & 856 & 0.5 & 978 \\ XC11493 Cuarcarchero & 27 s & 1666 & 1 & 1974 \\ XC220232 Cucarachero & 55 s & 99 & 0.03 & 57 \\ XC158418 Cardenal & 10 s & 627 & 1 & 2006 \\ XC32571 Zorzal & 15 s & 438 & 1 & 934 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Report of Modifications.  
Figure 4: Signal reconstructed of the XC3951 Solitario audio recording is shown before modification (**top part** of the figure) and after modification (**bottom part** of the figure), separated by channel.  
Figure 3: Signal reconstruction after modifying the Detail coefficient at a fourth transformation. The spread of the modification is signalized with the degradation of the modification.  
protocol and sound as the communication channel instead of the usually used RF signals. Building on this, nodes have preregistered bird sounds (preferably birds from that same region where the WSN is installed to avoid potential suspicions). In those sounds, the nodes will insert their data using the abovementioned procedure to avoid any perceptible signal distortion. Additionally, nodes will emit the bird's sounds (and, thus, send the packet data) and remain silent according to the statistical characteristics of these active/inactive periods, effectively implementing an _On/Off_ scheme.  
As such, we have \(N_{On}\) active nodes and \(N_{Off}=N-N_{On}\) inactive nodes at any instant of the system operation, where \(0\leq N_{On}\), \(N_{Off}\leq N\). These nodes perform their state change (_On/Off_) that follows poisson process behavior represented by \(\lambda_{On}\) to activate the node, and \(\lambda_{Off}\) to deactivate it. This variables are calculated from analyzing the expected value (\(E[x]\)), variance (\(\sigma_{x}^{2}(x)\)) and the variation coefficient (_CoV_).  
The transmission of data packets is measured using the following teletraffic metrics: throughput (\(\xi\)), the probability of having a free slot (\(F\)S), and the probability of packet collisions (\(P_{collided}\)). These metrics depend on the probability \(\tau\), which represents the likelihood of a transmission occurring in the current slot, the probability that only one node transmits during the current slot (\(P_{S}\)), and the probability of an idle slot (\(P_{F}\)).  
To calculate the system's lifespan, we determine the total energy available to the system (\(Total\_Energy\)), the energy consumption of transmitting nodes (\(Energy\_tx\) and \(tx\) respectively), the energy consumption of nodes that are turned on but not transmitting (\(Energy\_On\)), and the energy consumption of nodes in an idle state (\(Energy\_Off\)).  
Finally, we assess the system's capability to transmit bits per second (\(bps\)) by considering the bps capacity that each audio file can hide and the system's throughput.