On Making a bamboo Xylophone #4 (Qs Adam Peters)

-----Original Message-----
From: Adam Peters
Sent: Saturday, 17 November 2007 3:40 PM
To: jim@percussionclinic.com
Subject: Bamboo Xylo

I was reading two postings on your site about building bamboo xylophones. I am a High School student competing in a Science event called Science Olympiad. For my particular event I need to build a musical insturment. I am a somewhat proficent keyboard player, but I prefer Timpani. I seem to be on the right track as far as roughing out the bamboo bars, but I was wondering if you had any tips for me on the resonators. Most people in my event don't bother with the resonators, but if I can pull it off I might gain some points for accuracy of construction. I have a good supply of bamboo in the yard, but my largest pieces are only about 1.25 (in) in diameter. Any help would be much appriciated, thanks

~ Adam

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You should have no problems making resonators from the same bamboo you make your bars from. The length of hollow bamboo you need will be just a little less than ¼ the wavelength of the note the bar is producing. Find out the frequency of the note, then use v=fw where v is a constant - the velocity of sound in air (I forget at the moment, but an encyclopedia or quick google should fix that), f is the frequency, and w is the wavelength. Calculate ¼ the wavelength then cut your bamboo a little longer. There might be a little variation as the bamboo diameter may not be that consistent throughout the length. The end under the bar should be open, but the other end should be plugged - maybe with a wine cork or similar?? If the open end is smaller than the closed end, then the required length will actually be less, and vica versa. There is also a thing called end correction which just means that the ¼ wavelength length is shortened a bit in relation to the diameter of the resonator - I wouldn't worry about this, as the level of accuracy will not be that high anyway. Your best bet is to start a little long and gradually cut or sand the bamboo pipe shorter till it audibly works in position. A good idea would be to start with the highest note, then you first guess being a little long might work quite audibly under one of the lower notes. My making notes as you go you will find the lower notes easier to tune when you get to them!

All the best..
Jim McCarthy

For more help on instrument building you can email Jim.

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