Here are two questions my 6th grade Granddaughter came up with to strump her science teacher. Do you know the answers?

Question: Why do all “C” notes on the piano sound alike — just higher or lower, but sound the same compared to other notes? Same question for all “A” notes, “B” notes, and so on.

Answer: Because the vibrations per second are exactly doubled each time a C note appears on the keyboard. For example, the note most people refer to as “middle C” vibrates at a rate of about 262 times per second. (261.626 to be exact). The C one octave higher vibrates exactly twice as fast as middle C, or 523 times per second. The C one octave below middle C vibrates at exactly half the speed of middle C, or 130.813 per second. So the higher you go on the keyboard, the vibrations per second double with each octave. The lower you go on the keyboard, the vibrations per second are cut in half.

Reference:
http://en.wikipedia.org/wiki/C_(musical_note)
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Question: Why do some notes seem to harmonize together, while others don’t?

Answer: The overtone series, also known as sympathetic resonance. For example, when C is the fundamental note, the C one octave above it vibrates to some extent also, then the 5th above that (G), then the next C above that, then a 3rd above that (E), etc. It’s kind of like a family of notes — they all kind of sing together when the fundamental note is played.

References:
http://voices.yahoo.com/musical-overtones-hidden-tones-color-tones-498127.html?cat=33

http://howmusicreallyworks.com/Pages_Chapter_3/3_2.html

http://www.miqel.com/jazz_music_heart/vibrational-truth.html

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