比φ3mm平底孔回波声压小7dB的同声程平底孔直径是:()

2023-06-02

比φ3mm平底孔回波声压小7dB的同声程平底孔直径是:()

A.φ1mm

B.φ2mm

C.φ4mm

D.φ0.5mm



参考答案:

B