The Acoustic Approach: Renegade Soundwaves
Some specialist types of radar can detect drones by using the aircraft’s spinning rotor blades or by specifically detecting airborne targets with a small RCS (Radar Cross Section), but filtering out erroneous targets like birds. One drone detection technique which does not depend on radar is the acoustic approach.
Anyone who has seen a drone will be aware of the characteristic high-pitched sound of the aircraft’s motors and rotor blades. An acoustic drone detection system will use several microphones positioned on a mast. These microphones will receive ambient sound which will be fed into the system’s acoustic processor. The processor will be equipped with specialist software which will filter out extraneous sounds.
This approach is not unlike that employed by the dedicated drone detection radar which filters targets not behaving like drones either by their flight characteristics or lack of spinning blades. With extraneous sound filtered out, the processing software then ascertains the distance of the drone from the microphones and the drone’s location.
Location can be determined by triangulating the source of the sounds using the microphones. Two or more microphones can be used to determine the drone’s position by determining the relative strength of the sound waves coming from the drone’s engine and spinning blades. The more microphones the acoustic drone detection uses, the more detailed the determination of the drone’s position. Moreover, the microphones can help determine the direction in which the drone is flying.