Acoustic interference with Quincke (trombone) tube and sonalert.

Acoustic Interferometer: Interference with the Quincke Tube. Top section can slide in or out to adjust for positive or negative interference. Caution: After 3 maxima and minima, the device pulls apart. Avoid this.
UCB Index: 
B+35+5
PIRA Index: 
3B55.40
Demo Diagram: 

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