The wavelength and frequency of musical notes can be found here: http://www.phy.mtu.edu/~suits/notefreqs.html
A closed end pipe as used in the resonant speaker is a half-wave (half the given dimension). Note also there will be some "end effect" because the sound continues to vibrate past the end of the pipe - which means the pipe will need to be somewhat shorter than the true half wave. End effect is generally about 20% of the pipe diameter (from reading up on pipe design). I don't know what the effect of a 45 degree "end" would be but I suspect you would want to make the mid-point of the cut about where a square end would normally fall. One could also experiment with *closed end* pipes ... pipes with the far end plugged and a notch or hole near the speaker. Closed end pipes are a quarter wave long which would significantly reduce the size for those using low frequency tones. An open 700 Hz pipe is 49.5 cm (without end correction) - an open 440 Hz pipe would be 78.5 cm and a open 300 Hz pipe would be about 115 cm (nearly four feet!) long. Unfortunately, I have not seen any information on the sound port (notch) design for closed end pipes - or whether they can be driven by a speaker. 73, ... Joe, W4TV On 2/17/2017 1:56 PM, P.J.Hicks wrote:
Has anyone built the resonator with a straight length of tube? Perhaps terminated with a 45 deg. cut? Might be an interesting experiment. The 45 deg long radius street elbow in 2" is an order only item in my area so thought I'd substitute a straight length. PJH, N7PXY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
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