Passive acoustic localization based on time of arrival trilateration

Abstract

In Biology is very common the field researcher need to locate or to count subjects of determined specie. Sometimes, the animal cannot be seen but it can be listening, like is the case of the frogs and some birds. Localization and counting of individuals demand a lot of training, people, time and money. An automated device capable to count and locate sound sources, without seen them, is a very useful thing for biologists, police officers, tragedies attendants, military people, and engineers. Different of echo localization, like radar or sonar, in acoustic localization it is not possible to know the distance from the sound soured, a priori, because there is no synchronization. In the world wars there were some purely mechanical military devices using the sound emitted by the source, emulating big ears, trying to locate bombers at great distances. It was not found any work using multilateration of a real sonic source applied to biology. The passive acoustic localization based on time of arrival try to locate a sound emitter by processing the times that the sound takes to arrive from the source to the sensors, generally in number of three. Normal methods use heavy math to deal this. Here is presented a simple method using simple math to solve the problem of localization of a sound emitter. The results demonstrate successfully the concept, showing the problems, the errors and how to minimize them. The device will be used in field by biologists to counting an locating frogs and birds.