| 摘要 |
A whistle audibly responsive to extremely small pressure differentials is described. The whistle has a cylindrical inlet portion, a cylindrical outlet portion and a cylindrical constriction that form a passageway between said inlet and outlet portions. The whistle produces audible sound having an intensity of about 80 DB in response to a pressure differential, across the inlet and outlet portions, that is in the range of about 0.005 to 0.02 psi.
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