发一篇疑似阅读原文-中耳

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Modern industry has produced a noisy world. The din of jack­ hammers, the whine of jet engines and the blare of amplified electric guitars have become all too commonplace. It was therefore con­siderate of nature to have equipped the human ear with a rather sophis­ ticated noise-reduction system: two small muscles that are attached to the ossicles, the tiny bones that connect the eardrum to the cochlea (the struc­ ture that houses the sound-receptor cells). When the muscles contract, they dampen the vibrations of the ossicles, thereby reducing the acoustic signal that ultimately reaches the inner ear.

Although they are skeletal muscles (in fact they are the smallest skeletal muscles in the human body), the mid­ dle-ear muscles are not under volun­ tary control. They contract reflexively about a tenth of a second after one or both ears are exposed to loud external sounds. Indeed, the characteristics of the reflex have become so well known that deviations from the normal re­ sponse serve as a basis for diagnosing various hearing disorders and neuro­ logical conditions.
The muscles of the middle ear contract not only in response to loud external sounds but also immediately before a person vocalizes. This prevo­ calization reflex operates even when one speaks, sings or cries as softly as possible. Yet most evidence suggests that it is meant to protect the inner ear from the fatigue, interference and po­ tential injury caused by one's own louder utterances, which can result in high sound levels in one's head. The shouting and wailing of children or babies, for example, can reach their own ears with the same intensity as the sound of a train passing nearby.

The middle-ear muscles do more than just indiscriminately attenuate internal or loud external sounds in humans. The muscles muffle primari­ ly a loud sound's lower frequencies, which tend to overpower its higher frequencies. The net result of this fre­ quency selectivity is to improve hear­ ing-particularly of those sounds that contain many high-frequency compo­ nents, such as human speech. In fact, the middle-ear muscles are what en­ ables one to hear other people talking even while one is speaking.

Among lower vertebrates, birds pos­ sess the most elaborate systems for hearing and sound communication. In each ear they have a stapedius ana­ logue, which is attached to both the tympanic membrane and a single os­ sicle, the columella. Because a bird's stapedius muscle lies mainly outside the middle-ear cavity, it can be stud­ ied more readily than the stapedius of mammals without damaging the deli­ cate middle-ear structures.

肯定是略有精简

ihaveausdream

后面两段几乎一样了，特别有些用词都一样，什么muffle lower fre....什么其他vertebrates 例如鸟bla bla bla

中间的意思是一样的，就是收缩减小声音过大、和提前pre－vo­calization作用。

第一段没什么印象，感觉不大一样。。。

Sophiew17

gar_bbbbb 发表于 2017-11-6 03:47
看到jj有说人与鸟中耳的区别，我想补充一点。

Although the stapedius muscle of a bird always contracts ...

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不知道叫啥了

所以这次有重库嘛？求问

吃吃宸

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gar_bbbbb

看到jj有说人与鸟中耳的区别，我想补充一点。

Although the stapedius muscle of a bird always contracts during vocalization and swallowing, it does not appear to contract reflexively(反身地，反射地，和reflectively差不多) in response to loud external sounds.【对external sound没有反应】 The primary role of the muscle in birds, then, seems to be the prevention of sensory overload of the auditory receptors during the birds' own loud cries.【鸟类的中耳肌肉只减弱自己发出的声音】 Indeed, the screech of seagulls and the crow of cocks can result in sound-pressure levels of as much as 130 decibels (measured at the head)-about the level of noise produced by ajet engine 15 meters away.
来源：http://www.medizinisches-coaching.net/wp-content/uploads/2016/10/Mittelohrmuskeln_Borg_1989.pdf?x47477

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