http://phys.org/news/2015-11-vibrating-bees-state-hive.html
Researchers from Nottingham Trent University, in the United Kingdom, have now developed and tested a new prototype device that can remotely monitor hive activity without disturbing the bees. The device picks up and analyzes vibrations from special types of bee vocalizations, such as the common one called a “begging signal.” It has successfully tracked changes in bee activity from day to night, and seasonally, by monitoring the occurrences of this specific signal.