The radar microphone: A new way of monitoring honey bee sounds

This paper describes a radar microphone for studying incidental and deliberate insect sounds. It was specifically designed to record the sounds coming from honey bees inside a beehive. The sensor is based on a Doppler radar measuring the vibrations of a high dielectric object, such as a bee. It is shown that if the vibrational amplitude is much less that the radar wavelength, the frequency of the mechanical vibration and the frequency of the phase modulation in the reflected radar signal are the same. The instrument was implemented safely and inexpensively with readily available 5.8 GHz wireless components. The output of the radar microphone is a signal no different from the signal that might be recorded with an acoustic microphone. As such the same data collection and processing techniques can be applied. Examples are given of vibrations and airborne sounds from bees inside an observation hive.