That’s what happens when we attach a card to a bicycle so that it flaps against the wheel spokes as we pedal. If we make a clicking sound over and over at a regular interval, and begin to speed up the interval, it will start to sound like a note. So here’s a wonderful demonstration of how the frequency ratio of 3:2 actually produces the sound of a perfect fifth.
The vibrations of musical sounds occur very rapidly, anywhere from dozens to thousands of times per second… much too fast for us to count and verify their frequencies by ear.
When the ratio is 3:2 (that is, when one note’s frequency is 50% more than the other’s), they form a perfect fifth interval. When one note has twice the frequency of the other, the interval they make together is an octave. When you play two notes together, the musical interval they form is determined by the ratio of the notes’ frequencies. Increasing the frequency of vibration raises the note’s pitch decreasing it lowers the pitch. Every sound that is a musical note is characterized by how many times per second the vibration occurs. Watch it first if you want to figure out for yourself what’s going on… or read on for an explanation.įirst a little background about sound waves (skip it if you’re familiar): All sounds are vibrations of air molecules. Here’s a beautiful audio/video demonstration of a simple acoustic principle.
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