The rooster’s crowing is so loud, why haven’t you gone deaf yet?

Gulp! ...

My eyes are hurt. ｜Giphy

How loud is a rooster crowing? In decibels, it's about the same as a large truck speeding past you, or someone operating a lawn mower in your ear.

Someone measured the sound of a rooster crowing at a distance of 1 meter and found that the sound level reached 100 to 126 decibels. You should know that the sound of a chainsaw is about 120 decibels. In the early morning when you are woken up by the crowing of a rooster, it is like a chainsaw causing devastating damage to our eardrums and brains.

Just a quick search will reveal that there are quite a few victims who have been woken up by the crowing of roosters.

You know, just like listening to the sound of a chainsaw for a long time, listening to the crowing of chickens for a long time will also damage your hearing.

Sometimes when we stay in a noisy environment for a while, the sounds we hear in the next few days will become deeper. This is a temporary threshold shift, and the ear will take some self-protection mechanisms in the noise. However, when the sound is louder and lasts longer, the ear's self-regulation mechanism will not work, which will cause more serious hearing damage.

Long-term exposure to noise levels exceeding 70 decibels may damage your hearing, and noise levels exceeding 120 decibels may immediately cause damage to your ears.

Stay safe and stay away from noise! ​​｜Giphy

The researchers placed a small microphone in the chicken's ear to measure the volume of the sound transmitted to the chicken's ear. Of course, in order to be able to withstand the "chainsaw volume" of the chicken's crowing, the microphone is also powerful enough to measure sounds over 140 decibels. Sure enough, people found that when the chicken crows, the sound transmitted to the chicken's ear is as high as 130 decibels.

The microphone is on! ｜Reference [1]

Since sound can cause direct hearing damage to both humans and birds, why don't roosters deafen themselves when their crowing is so loud?

People discovered that the magical protective mechanism appeared in the chickens' own ears.

The researchers analyzed the ear structures of roosters by CT scanning when they opened their mouths. They found that when roosters crow, that is, when they open their mouths as wide as possible, their external ear canals close up, just like wearing earplugs.

The ear canal structure of a rooster is shown in Figure A (before crowing) and Figure B (when crowing). The ear canal structure of a hen is shown in Figures C and D. | Reference [1]

At the same time, when the chicken's beak is opened to the maximum, the soft tissue in the ear canal will directly cover 50% of the eardrum. In other words, the ear plug is tightly plugged and thicker. In addition, the crowing of the rooster will also affect the muscles related to the auditory ossicles, which can also achieve a noise reduction effect of 10 to 20 decibels.
In other words, even if the rooster clucked and cuckooed for an hour, he himself would feel as if he was wearing noise-canceling headphones and life would be peaceful. Maybe he would even cuckoo more loudly.

But hens may be deafened by roosters, because studies have found that compared with roosters, hens have a smaller degree of reduction in the diameter of their external auditory canals due to some structural differences in their mandibular muscles. After all, the sound of a hen's call is already smaller, reaching only about 70 decibels.

It seems that the only way for hens to protect their ears is to stay away from roosters. Maybe the same is true for us if we want to protect our ears.

It's not just chickens that have learned the noisy trick of self-preservation, cicadas have done the same. In some areas of the country, the sound of cicadas is deafening in the summer, but as the loudest insects, they are not deafened by themselves. Cicadas have ears and auditory receptors. When they hear a sound, they contract their abdominal muscles, causing the eardrum on their abdomen to contract and produce nerve impulses. Don't they hear the sound of their own chirping?

In fact, it is really inaudible. After measurement, it was found that the most sensitive sound of a male cicada is 2.1kHz, but its scream frequency is 4.5kHz. Its eardrum is not sensitive to the frequency of its own scream, so it does not sound so harsh.

Cicadas will not be deafened by their own noise. | Pixabay

People have discovered that, like chickens, they also have a self-protection mechanism. When a male cicada calls loudly, its tendons contract and wrinkles appear on its auditory membrane, reducing its sensitivity to sound.

Female cicadas are also victims, as their eardrums are sensitive to the frequency of male cicadas’ chirping sounds. But this is easy to understand, since male cicadas chirp to find a partner.

When a rooster crows, it is actually declaring its sovereignty. According to reports, when crowing, the roosters do not crow randomly, but follow a certain order: the roosters with higher status crow first, followed by the roosters with lower status, and the crowing order must be strictly followed.

Because crowing also means "this land and the hens are mine!"

I'm the boss, understand? | Pixabay

Cover source: Pixabay

References:

[1] Claes, Raf, et al. "Do high sound pressure levels of crowing in roosters necessitate passive mechanisms for protection against self-vocalization?." Zoology 126 (2018): 65-70.

[2] Sueur, Jérôme, James FC Windmill, and Daniel Robert. "Sexual dimorphism in auditory mechanics: tympanal vibrations of Cicada orni." Journal of Experimental Biology 211.15 (2008): 2379-2387.

[3] https://phys.org/news/2015-07-cock-roosters-crow.html

END

This article is reprinted from "Bringing Science Home"