The Sounds of the Bees (putting a microphone inside the hive)

Once the swarms had begun to establish themselves, I became increasingly curious about the hidden world inside the beehive. I knew it was not sensible to disturb the colony without good reason, so resisted the urge to open-up and prod-about. Instead, I watched at the entrance – learning to spot the difference between worker and drone, and, as spring turned to summer, to identify the colours of the pollen carried back from the allotments. But I still couldn’t shake the feeling that I should be ‘doing’ something – something more than the occasional inspection. My hands were restless.

I became intrigued by different ways of observing the bees, especially listening to the sounds they made. At the entrance of the hive, I found I could sense some of the activity with my eyes closed. A bee on a foraging flight makes a distinctly different buzz from the guard-bee investigating a visitor. And the zippy fighter-jet-sounds of scavenging wasps contrasted with the deep, slow bombers of the bees.

with a stethoscope, we could hear the bees more clearly

The sounds from inside the hive fascinated me most. Pressing my ear to the lid, I could identify how far the colony had built its comb. I borrowed a stethoscope from a bee-loving student-nurse, pressed that to the side of the hive, and got a louder and clearer insight into the bees’ communications. The sound seemed to change with the mood and the weather – at night it seemed softer; on warm days, more frantic.

I wanted to hear more from inside the hive, so I built an in-hive microphone. I modified a spare top-bar to hold an electret microphone-element, and built the circuit to power it. The whole assembly attached to a miniature guitar-amp, so with the flick of a switch, the hum of the bees could be made as loud as a human voice. Full instructions for building it are included below.

the circuit board for the microphone

If I got home late from London, I would hurry to the back garden to hear the midnight whisperings of the colony. Once, as I crouched by the hive with headphones and circuit-board in hand, a guard bee on night-watch flew out to investigate my presence. I was in awe of her bravery – launching herself out into the near-total darkness to warn me away from the hive.

Later, I extended the speaker-wire across the garden, and up through a vent in the kitchen window. Instead of turning on the radio while we do the washing-up, my housemates and I can stand in the kitchen and “switch on the bees”. We are serenaded by their low buzz, occasionally punctuated by the frantic whirr of an individual bee passing over the microphone. I was originally concerned that the bees might take a dislike to the metal and encase it in propolis, but after five-months inside the hive it is still working.

There are ways to take a more scientific approach. I could record the sound and analyse the frequencies, to discover how the hum changes with the hours and the seasons. I could try to translate the clicks and squeaks of their language. But for now I will get home late from work, switch on the kettle and the bees, and eavesdrop on the music of their murmured conversations.

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Building a beehive-microphone

parts required for building a beehive microphone

To build a beehive microphone, you will need…

• A bar/frame of the appropriate type for your hive
• An electret microphone element*
• A 0.1μF capacitor*
• A 2.2 kΩ resistor* (marked with three red lines)
• A small strip of wood for the microphone housing (an old spacer-bar is ideal)
• Nails (around 1-inch long)
• 9v battery
• 9v battery connector* (not essential, but helpful)
• Speaker wires – long enough to stretch from your hive to the amplifier)
• Short wires (lengths of any wire work perfectly, but crocodile-clips on the ends make everything easier.)
• A cable with a minijack connector on one end (this can be made by chopping the earpieces off an old pair of headphones)
• A ‘breadboard’ – a chunk of scrap wood on which you will build the circuit-board. A flat offcut about the size of your outstretched hand is ideal.
• Amplifier/speakers – I used a Fender mini-amplifier, which would cost about £30 new. You can wire the board up to your home hi-fi system if the wires are long enough.

(* I have spares of the asterisked components. If any local beekeepers want to make this, I’m happy to send you some – reply to this post and we’ll sort something out).

There are two parts to building the system. The first is the modified frame, which will sit inside the hive — you might need to adapt this for your hive-type. The second is the circuitry which powers the microphone, and sends the signal to the amplifier.

The part inside the hive…

microphone on a top-bar, showing the ‘inverted Stonehenge’ arrangement

An electret microphone is about the size of three shirt-buttons stacked together. The challenge is to put the microphone somewhere near the middle of the hive, without disrupting the bee-space. For a top-bar hive, I cut a spacer-bar into three pieces, and built an ‘inverted stonehenge’ arrangement on the underside of a spare bar – making sure it was as wide as a honeycomb. A hole drilled through the bar provides space for the wires, and the microphone hangs freely in the centre.

One leg of the microphone is soldered to the body of the microphone. This is the grounded leg (and will connect to the negative terminal on the circuit board).

I originally put some plastic mesh to enclose the microphone-space. The bees chewed through the mesh, but even with access to the electronics they’ve not done any damage. I don’t think the mesh is necessary, but you can pin some on if you’d like to.

The part outside the hive

diagram showing the setup of the wiring

For a quick overview of what we’re doing, this video is an excellent starting point. The circuit we’re building is shown in the diagram.

First, take the breadboard, and hammer in some nails (black dots on the diagram).
Then, attach the capacitor and resistor to the nails. If the nails are the right distance apart, it should be possible to wrap the ‘legs’ around them.
Add the battery, and connect to nails.
Then, attach the minijack cable. If it has two small internal-wires, connect it one way round, and reverse it if it doesn’t work when you test it. If it has three wires, two of them (+) should connect to the capacitor, and one (-) will go to the negative battery terminal. In mine, the blue wire was the negative one and red-and-white were positive – yours may differ.
Attach the other wires to connect everything together. If you’ve got crocodile-clips this is easy – if not, twist the ends of the wire around the nails.

Bringing the parts together

The next stage is to test it – it’s probably best to do this before going anywhere near the bees. First, plug the minijack cable into the amplifier (you might need some sort of adapter, depending on the inputs on the amplifier).

Then attach the wires from the microphone to the circuit board. The leg which is soldered to the metal casing of the microphone should be connected to the negative terminal.
Switch on the amplifier, and blow gently on the microphone to test the circuit (it’s easier to hear than testing it by speaking).

If it’s not working, try reversing the coloured wires from the minijack-cable. A multi-meter might help with finding any loose connections.

comb built around the microphone-enclosure

Disconnect the microphone, and put the bar (or frame) inside the hive. Reconnect all the the wires, and listen to the bees.

Please note – even if amplifier is switched off, the microphone is still ‘on’. Disconnect the battery when not in use to prevent using up power (and potentially annoying the bees with constant electrical-current running inside the hive).

 

🐝 🐝 🐝

Jack Pritchard, Oxford/Southwark, October 2016