Sounds of insects

When you previously talked about "which side of the brain we use to hear sounds," you said you'd talk more about insect sounds later, right?

Ah, you mean how Japanese people listen to the sounds of insects and nature with the left hemisphere of their brain, the part that handles language.

Do people from other countries simply find the sounds of insects to be noise?

Indeed, it seems that people in America and Europe don't particularly associate insect sounds with the seasons. I once heard a story about a joint Japanese-American film project. When the film shot in Japan was sent to America, they received a complaint that there was noise and that they had to reshoot. However, upon investigation, it turned out that it wasn't noise at all, but rather the sound of cicadas because the footage was shot outdoors in the summer. For Japanese people, the sound of cicadas is a symbol of summer, so it wouldn't seem strange to have it as background noise, but to Americans, it probably just sounded like noise.

Are there no cicadas in America?

It seems to depend on the region, but apparently they don't all make loud noises at once during the Japanese summer. I've also heard this story: I think it was quite a while ago, but when Ueno Zoo bought elephants from Germany, a German stayed for about two months to provide guidance on how to care for them. When the German was about to return home, Ueno Zoo asked him what he would like as a thank you gift, and he said, "I want that tree that makes noise."

Were you referring to the tree where the cicadas were chirping?

That's right. I didn't realize it was the sound of cicadas.

Last year in Japanese class, we read Yasunari Kawabata's "The Sound of the Mountain." My teacher said that it would be difficult to explain the opening line, "It's ten days before August, but the insects are chirping," to a foreigner.

My dad has heard that story too. The translation by Seidensticker, an American Japanese scholar, is "Though August had only begun, autumn insects were already singing." But the idea that insects are singing doesn't connect to the feeling of the season, so the meaning is hard to understand.

There's an interesting example of analyzing insect sounds. These are the sounds of a cricket and a bell cricket; listen to them first. Can you tell which is which?

Crickets make a "reen-reen" sound, right? The first sound I heard was a nicer sound, so is this the cricket sound? (Insect sound 1)

Correct! The sound of the cricket certainly sounds nicer. Analyzing these two sounds yielded some interesting results. First, when comparing them using 1/3 octave band analysis, there is almost no difference, as shown in Figure 1.

But I did think that the pitch was quite similar.

That's right. In both cases, the 4 kHz and 5 kHz frequencies are prominent. Next, if we plot a map using the fluctuating sound analysis that we used before for the shamisen and the "crying dragon" sound analysis, it's just as similar. (Figure 2)

Does this mean that even with fluctuating sound analysis, it's impossible to detect the difference between crickets and bell crickets, which sound so different?

My dad thought the same thing at first. He felt that the cricket's sound was rough, so he thought there would be a difference if he put it through fluctuating sound analysis. Just like how we were able to detect the roughness and coarseness of the "nakiryu" and shamisen sounds that we analyzed before. But it turned out to be simply a matter of the scale of the map axes. Both are definitely fluctuating over time at the same frequency/fluctuating frequency, but the magnitude of the fluctuations is different. This is a diagram (Figure 3) where we matched the axis scales, and we found that the magnitude of the cricket's fluctuation is numerically about 15 times that of the bell cricket.

Is the reason insect sounds fluctuate over time because they produce sound by periodically vibrating their wings?

Insects like crickets have a part of their body called an affricate organ that produces fricative sounds. On the veins of their wings, there are fine, saw-tooth-like projections on the branched veins, and they produce sound by rubbing these veins together at high speed with their legs.

It's interesting how the differences become clear when you extract the components that fluctuate over time, not just the pitch and volume, of sounds like the shamisen, the sounds of insects, and the sounds created by the space, like the "singing dragon."

That's right. In the case of friction noises generated when various machines are in operation, the frequency and fluctuating frequency are related to the sound generation mechanism, so that information becomes important for noise and abnormal sound countermeasures and sound creation.