The air in the middle ear cavity also expands and contracts with changes in atmospheric pressure. 中耳腔内的空气会随气压转变而膨胀或收缩。
The Straight Sided Insert is a threadless check valve designed to be inserted into any cavity where a check valve is needed and threads are not desired. 直面插入式阀门是一款用来插入到任何需要止回阀但不需螺纹的空腔内的无螺纹止回阀。