问题描述：
"once and
全句是：
In most sound designs,air showers over the critical area once and then is systematically exhausted from the enclosure.
最好把全句都翻译一遍!
全句是：
In most sound designs,air showers over the critical area once and then is systematically exhausted from the enclosure.
最好把全句都翻译一遍!
问题解答：
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