You might expect to hear an angry buzzing when honeybees have been disturbed. But some apiarists reckon they can also deduce the condition of their bees from the sounds they make. A steady hum could be the sign of a contented hive; a change in tone might indicate that the bees are about to swarm. That intuition is about to be put to the test. Soon, beekeepers will be able to try to find out what is troubling a colony by listening to the buzz using a smartphone app.