TOKYO -- Sohgo Security Services, commonly known as Alsok, will roll out a service this month that can serve as a sentry by listening for drones around government buildings and other important sites.
Tiny unmanned aerial vehicles fly under the radar. When they operate autonomously, there is not even a radio signal from a remote controller to detect. But the Tokyo company's new service is based on detecting sounds -- the spinning propellers serve as an audio fingerprint identifying every make of drone.
