Capturing the Ultrasonic Sounds of Insects

It all started with recording a bee with a Sanken CO-100K. This microphone is a real sound microscope ! Playing back the recording at 1/4 speed, I could hear the bee’s wings flapping, which my Neumann KMR81 did not catch at all.

I experimented with other insects near my home and I discovered that their stridulations contain a lot of sound in the ultrasonic domain, sometimes more than in our hearing range. It was a new world available to my ears and a new material to create new sounds from. Insects, and in particular orthoptera (crickets and grasshoppers), emit rich and varied sounds from one species to another. My orthoptera guide book even says: each species capable of singing has its own unique song.

I thought: why not create a sound library with insects like we’ve never heard them before?

I thought: why not create a sound library with insects like we’ve never heard before? Very close-miked, perfectly isolated from background noise and containing all possible frequencies up to 100,000 Hz? Like a solo musician in a studio? With such a library, we could do many things: 

• Multiply insects with softwares like Sound Particles to make swarms or unusual soundscapes.
• Pitch sounds down to explore ultrasonic frequencies.
• Use sounds, pitched or not, as a base to create monsters, animals, engine, UI or computer sounds.
• Use tonal songs to create virtual instruments or synths.

That’s how the idea for the Ultrasonic Insects library was born.

I started recording insects near my home. I am lucky to live in the South of France, a region that has the greatest diversity of singing insects in the country: hundreds of species of orthoptera and a dozen species of cicadas.

The black cicada – Cicadatra Atra – always sings head down

When recording insects in the wild, I encounter several challenges. 

First I had to find one specimen in the quietest environment possible, because the CO-100K is an omnidirectional microphone and it picks up any audible or ultrasonic sound in almost all directions. This includes of course other insects, which means a field with hundreds of grasshoppers is not the best place to record an isolated specimen. 

The next step is to approach the insect. It’s usually at this moment that it stops singing, because insects have very good eyes and can see me from a distance

The next step is to approach the insect. It’s usually at this moment that it stops singing, because insects have very good eyes and can see me from a distance. So I wait and stand still (sometimes for a long time) until it starts singing again. Step by step, I come closer, until I can bring my microphone a few centimeters away from the insect. (the closer the better, there is no proximity effect on an omnidirectional microphone).  This can take a while, and it’s often disheartening when the grasshopper I spotted for 20 minutes flies away. After many trials, I perfected my approach technique with very slow movements and a lot of concentration. I guess it’s a bit like hunting, without killing your target!

The nearby insect recording exercise is more or less difficult depending on the species. The southern wart-biter, for example, detects you more than ten meters away, and stops singing for minutes. On top of that, it hides in very thick bushes. It took me several hours to get a good recording. In contrast, the Saddle-Backed Bush Cricket is not fearful, willingly sings and can even be taken in the hand without running away.

Ephippiger

Besides, I had a surprise when recording this same Saddle-Backed Bush Cricket. Its song is quite audible, but doesn’t sound louder than those of other locusts. When I moved my Sanken towards it, the input of my recorder immediately clipped. I had to lower the gain by about 30dB for the signal to modulate correctly. In fact, its song is very loud, but most of the energy is between 20 and 25 KHz (which I can’t hear!).

After recording, I took some pictures of my specimens to add to the metadatas and identify the species. Identification is quite a hard process unless you are a specialist. Color is not a good clue because it varies a lot within one species. It was a real investigation, using guide books, comparing spectrograms and sometimes asking help from insect specialist online groups.

Subsequently I recorded 3 crickets species which are usually sold to feed reptiles. For the recordings, I transformed my studio into an almost anechoic room by adding many absorbing panels. Indeed, the studio’s short reverberation becomes very noticeable when slowing down recordings.

For the recordings, I transformed my studio into an almost anechoic room by adding many absorbing panels

I ordered crickets and I used a cage with plastic mesh to give them space to express themselves, which was very successful. I got hours of recording for each species. I then released my crickets into the wild.

Gryllus bimaculatus

I discovered the existence of Madagascar hissing cockroaches by chance.

They are able to emit quite loud sounds to scare away their predators, which is unique among insects. Their sound mimics a snake hiss. I approached a breeder to get different specimens. The Madagascar cockroach is a large insect, among the largest in the world (up to 10 cm).

The first time, the hiss literally startled me – you would never imagine such a sound coming from an insect

When you touch its shell, it triggers a hiss as a protective reflex. The first time, the hiss literally startled me – you would never imagine such a sound coming from an insect. Subsequently, I took time to get to know these harmless little beasts that looked repulsive at first glance. I recorded them carefully, trying not to stress them too much. Finally I decided to keep them and offered them a nice terrarium.

I crisscrossed my region during the whole summer to collect a total of twenty insect species (plus five recorded in my studio).

I noticed that each species has its own specific song and frequency range, like radio frequencies in radio-communication – maybe to prevent interference between species?

I noticed that each species has its own specific song and frequency range, like radio frequencies in radio-communication – maybe to prevent interference between species?

Some species vary the pitch of their song a lot depending on the temperature, such as the Italy Tree Cricket (there are two different recordings in the library).

I also discovered insects use different parts of their body to produce sound. Cicadas have two cymbals in their abdomen. Most grasshoppers scratch their huge hind legs against their body. The crickets produce tonal sounds by rubbing their small wings against each other (their wings do not allow them to fly). And finally the hissing cockroaches force air through their stigma (tiny holes that allow breathing) to produce spectacular hisses.

I hope you’ll enjoy this first volume of Ultrasonic Insects as much as I enjoyed recording it.

To be continued next summer for a second volume.

Please share this: