A whistle for producing resonant frequencies comprising a body which includes a mouth piece having an inlet, and at least two sound chambers to which inlet air is blown from the inlet. The whistle further includes air passageways for communicating inlet air from the inlet to the sound box and sound chambers....http://www.google.ca/patents/US8028642?utm_source=gb-gplus-sharePatent US8028642 - Whistle with finger grip
