| 摘要 |
A sound collecting device for acoustic boards including a conical hood formed with a flange at a large end and external threads under said flange, the conical hood having a plurality of perforations with different sizes and an annular groove at an inner surface of a small end thereof, a front silencer being a tubular member having a hemispherical top and an open bottom, the front silencer having a plurality of perforations with different sizes and being formed close to the bottom with an annular projection adapted to engage with the annular groove, and a rear silencer being a tubular member integrally formed with the small end of the conical hood and having a conical recess at an outer end thereof.
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