Non destructive testing . tightness testing . testing by accumulation or sniffing of gas 无损检验.密封性试验.用蓄气或吸气进行检测
2.
Close tightly your lips with air in your mouth ; then the breath break through your lips and make resonance inside the oral cavity 发音时,双唇紧闭,口腔蓄气,然后气流冲破双唇阻碍,在口腔发生共鸣而发声。