These prevent the occurrence of a certain noise,   which normally arises when air blows into tank pressure equalization openings inflight. The  effect is similar to blowing over a glass bottle.

这些可以防止出现某种噪音，这种噪音通常在空气吹入罐压力平衡开口飞行时出现。效果类似于吹过玻璃瓶。