The gentle sound of bees buzzing among the flowers: a favourite sound of Summer. But why do bees buzz, and how do they make that buzzing sound? Bees buzz for two reasons. First, the rapid wingbeats of many species create wind vibrations that people hear as buzzes. The larger the bee, the slower the wingbeat and the lower the pitch of the resulting buzz. This is a phenomenon of the wingbeats and not specifically of bees–some flies, beetles, and wasps also have buzzy flight caused by their wingbeats.
Buzzing isn’t just for show, however — it also serves an important purpose. When certain species of “buzz-pollinating” bees, such as bumblebees, visit a flower, the buzzing and vibrations of their wings and bodies cause pollen to shake off the flower. The pollen then attaches to the bee’s body and is deposited on the next flower the bee stops to visit. This transfer of pollen from flower to flower is called “pollination.”
One particular type of high-pitched buzzing sound made by honey bees is called ‘piping’. Piping occurs directly prior to swarming, but can also occur during the disturbance of a hive. There are differing views about which bees in the honey bee colony initiate the piping prior to swarming. Some sources state that the queen starts first.
Whatever the truth of this, it seems that the buzzing sound made by bumblebees is at least greatly amplified by the vibration of the wing membranes.
Source: wonderopolis.org, www.buzzaboutbees.net, www.scientificamerican.com