♠/Slide whistles and harmony/Beats simple

CNX_UPhysics_17_06_beats.png

The top and bottom graphs of time versus pressure in this audio signal are related. The graph show two signals. When you add them together you get the bottom graph. When the two signals add together it is called destructive interference. Constructive interference ~~occurs when the parabola~~^[1] can be seen when the peak of one signal matches the other's and the amplitude ~~increases~~ is maximized. Since this is a signal of pressure versus time, the constructive an destructive events alternate in time, create a loud-soft repetition known as beats.^[2]

Footnotes

Student drafts at 02.pdf.
Click for 2Hz beat frequency 'emerging' from tones at 220 and 222 Hz. Also, szynalski.com can be used to open two tone generators in adjacent tabs.

↑ Parabola? Yes it does look like on
↑ AKA what music teachers call the "wa-wa"

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[1] Parabola? Yes it does look like on

[2] AKA what music teachers call the "wa-wa"