Airdate: Nov 04, 2010
Scientist: Bart Hopkin
Sounds - Frequency and Math
They're playing my favorite equation!
JM: When you listen to your favorite song, you're probably not thinking about the mathematical equations that make that song possible. I’m Jim Metzner and this is Pulse of the Planet.
Every musical note we hear resonates at a certain frequency that’s the speed of the vibration we hear as sound as it moves through the air. Lower notes vibrate at a lower rate a low frequency of vibration, and higher notes vibrate faster they have a higher frequency. There is mathematical relationship between the notes of a musical scale.
BH: The octave is the simplest relationship. It’s a doubling of frequency.
JM: Bart Hopkin is a musical instrument builder, who’s part scientist and part musician and one of the key players in this year’s Kids’ Science Challenge our free, nationwide competition for third to sixth graders. He tells us that every note in the scale has a specific frequency. For example, an A’ vibrates at 440 cycles per second. Another A’ played an octave higher vibrates at 440 cycles per second.
BH: And the other pitches are arrayed in between. For instance, if you go from that A up a fifth to the E, the frequency relationship between the lower A and the high E is going to be, ideally, three over two these ratios represent the basic musical intervals, and each interval has a ratio associated with it, that’s what the interval is.
JM: That’s important information for Bart Hopkin. He’s spent his career building new musical instruments, playing with these mathematical equations to create new sounds in new ways.
BH: Imagine you’re making a wind instrument, and it’s, let’s say, something like a Pan pipe where there are many tubes and the longer the tube is, the longer time it takes the sound waves to reflect back and forth, that means the lower the frequency’s gonna be because it’s a longer time between each pulse that comes outta the end of the tube.
JM: Do you know a third to sixth grader who wants be a scientist-mathematician-musician and create a brand new musical instrument? Have them check out, kidsciencechallenge dot com. Pulse of the Planet is made possible by the National Science Foundation. I’m Jim Metzner.