Description

2. Background Review

2.1 History

Target acoustic monitoring has been involved in human development for centuries. There are tens if not hundreds of methods for acoustic localisation. These range from acoustic emission monitoring [12] all the way to heart sounds localisation [13]. Its involvement denoted significant progress regarding environmental, stress-related, and wildlife monitoring. And every single one of these domains would benefit from the implementation of WASNs. Environmentally, implementing a WASN could aid with noise monitoring in urban areas while also cutting the cost of noise mapping in half [4,6,15]. Concerning the wildlife, the range and accuracy enhancement of a WASN brings major benefits compared to simple microphone arrays [16]. Regarding humans, hearing aids can adopt WASNs for the ear microphones to becomes smaller and more effective in noise cancelling, with real-tie implementation [17].

The localisation of a target through acoustic means can be achieved with an abundance of methods, though it mostly refers to determining the distance and direction of that specific target. The categorisation can firstly be separated by active and passive. The active acoustic localisation involves creating a sound of which echoes identify and analyse potential sources. The passive one implies a similar methodology, just that the source produces its sound, which is in its order detected by the localiser. For this project, the focus is on the passive method. This approach is then expanded upon and separated into:

⦁ TOA Estimation

⦁ TDOA Estimation

⦁ SPP using VAD

⦁ Triangulation

2.1.1 TOA Estimation

Time-of-arrival (TOA) techniques are generally used for 5G access and localisation systems to gather parameters such as distance to target, distance from target to microphones, and general outside noise [18]. The estimation itself aids in acoustic synchronisation. The process starts with a signal sent from a sound source to the transmitters. This is then further transmitter to the receiver and compared with a set parameter and is deemed to be either the actual source location or background noise. The negative side of such a transmission comes from the loss of accuracy in signal detection when it comes to nonlinearities in the transmission chain, since perfect waveforms cannot be achieved [18]. Thus, Figure 2 has the following parameters:

Parameter Description

Dx Distance between target and node

Sx Nodes S, where x = {1,2,3}. Centre of Ri

Rx Circle intersected with the target, radius of Sx

Table 1: TOA Signal Capturing Parameters

Instruction Files