(Kelly of the Clue Crew gives the clue from a lab.)  Stretch a balloon over a glass, secure with rubber bands, then place a straw on top & you have a simple version of this device that measures air pressure
Under the Bernoulli Principle , there is then a lower air pressure on top 
of the... [DOC] [TLE] Full text of "The Flying Circus of Physics ( With answers )" [PAR] It is just simple standing waves set up on the plate by the bowing?