A rooster’s crow has been called the alarm clock from hell. It is loud and piercing but eventually winds down. So how do the hens tolerate the noise? Why don’t they get migraines?
“ … To find out, researchers attached recorders to the heads of three roosters, just below the base of their skulls. Crows lasted 1 to 2 seconds and averaged more than 130 decibels. That’s about the same intensity as standing 15 meters away from a jet taking off. One rooster’s crows reached more than 143 decibels, which is more like standing in the middle of an active aircraft carrier.
The researchers then used a micro–computerized tomography scan to create a 3D x-ray image of the birds’ skulls. When a rooster’s beak is fully open, as it is when crowing, a quarter of the ear canal completely closes and soft tissue covers 50% of the eardrum, the team reports in a paper in press at Zoology. This means roosters aren’t capable of hearing their own crows at full strength. The intensity of a rooster’s crow diminishes greatly with distance, so it probably doesn’t cause significant hearing loss in nearby hens.
But if it did, she’d likely be OK. Unlike mammals, birds can quickly regenerate hair cells in the inner ear if they become damaged”.
https://www.sciencemag.org/news/2018/01/how-roosters-protect-themselves-their-own-deafening-crows