Slowly, tenderly, the father stretched forth his hand and raised the thick, reddish-brown hair to reveal that the mother had no outer ears.

慢慢地，轻柔地，爸爸伸出手撩起了妈妈那浓密的红色的头发，显露在孩子面前的竟是：妈妈没有耳朵！

So, when they tilt their head, it's likely because they're adjusting their outer ear, so they can better pinpoint where sound is coming from.

因此，当它们歪头时，可能是因为他们正在调整外耳，这样它们可以更好地确定声音从何而来。

The first is called conductive, which is any kind of problem with the outer or middle ear, where sound can't make it to the inner ear.

第一种称为传导性，这是外耳或中耳出现的问题，在这种情况下，声音无法传递到内耳。

Humans normally hear using air conduction with sound waves passing through the outer and middle ears and causing the inner eardrum to vibrate.

人类通常通过空气传导听到声音，声波穿过外耳和中耳并引起内耳膜振动。

Wax in the outer ear canals and tears from eye ducts can slow the growth of some bacteria. And stomach acid can destroy certain swallowed germs.

身体的第二道防线是在血液和淋巴里。某些白细胞群聚集在感染区，并通过形成脓块使感染局限化。

Now, the middle ear, also called the tympanic cavity, is the relay station between the outer and inner ear. Its main job is to amplify those sound waves so that they're stronger when they enter the inner ear.

现在，中耳，也称为鼓室，是外耳和内耳之间的中继站。它的主要工作是放大这些声波，以便它们进入内耳时更强。

The outer ear picks up sound waves from the air around it and moves them along your ear canal to the middle ear, where the sound waves vibrate the eardrum, sending the sound along to the inner ear.

外耳从周围的空气中收集声波，然后将其沿耳道传递到中耳，声波会在此振动耳膜，从而将声音传递到内耳。