From the video description
In search and rescue missions, Micro Air Vehicles (MAV's) can assist rescuers to faster locate victims inside a large search area and to coordinate their efforts. Acoustic signals play an important role in outdoor rescue operations. Emergency whistles, as found on most aircraft life vests, are commonly carried by people engaging in outdoor activities, and are also used by rescue teams, as they allow to signal reliably over long distances and far beyond visibility. For a MAV involved in such missions, the ability to locate the source of a distress sound signal, such as an emergency whistle blown by a person in need of help, is therefore significantly important and would allow the localization of victims and rescuers during night time, through foliage and in adverse conditions such as dust, fog and smoke.
In this work we present a sound source localization system for a MAV to locate narrow-band sound sources on the ground, such as the sound of a whistle or personal alarm.
Basiri, M., Schill, F., Lima, P. U., & Floreano, D. (2012, October). Robust acoustic source localization of emergency signals from Micro Air Vehicles. In Intelligent Robots and Systems (IROS), 2012 IEEE/RSJ International Conference on (pp. 4737-4742). IEEE.
(Via Robots Dreams)