With a weekend off from playing at weddings I made an escape out to Tarbert on the west coast to visit my grandparents. My grandpa is a beekeeper and so I took my microphones to take some bee sound recordings.
Honey bees flap their wings at a rate of approximately 190-250 times a second and sure enough a spectral analysis of my recording reveals a dark band within this frequency range. The lowest dark band represents this fundamental (1st partial) tone that the bees produce and the larger dark band above represents the 2nd partial harmonic which occurs at double the frequency of (or an octave above) the fundamental tone. Above the 1st and 2nd partials the harmonics of the swarm become weaker and less distinguishable from the background ambience. When a bee flies close to the microphone however a clearer spectral signature can be seen (an example is highlighted why the red box below). Now that the bee is closer more of the constituent harmonics of it's 'buzz' are visible.
Research has suggested that the frequency of a honey bee's buzz can vary depending on the age of the bee, it's role within the hive and the overall health of the hive. Interestingly, it was long thought that honey bees are deaf, however, more recent research claims that they can hear sounds of up to 500Hz. This is within the range of the buzzing sound that they make with their wings (see the above spectrogram) and it is thought that the bees may use this sound to communicate during their famous waggle dances.
There are countless interesting routes for further study of the sound of bees. How does the pitch of a hive vary through the year? How does the size of a bee and it's social status or role within the hive affect it's sound? Can the mood of a bee be determined by analysing it's buzz? Hopefully I will find the time to return to the hives at Tarbert and answer some of these questions in the not to distant future!