Please pardon my late response but I need to underline something Lloyd had to say on "closed quotient".
Lloyd's mention of a satisfactorily QUICK transition from the closed to the open condition and the opposite, brought me round to the consideration of a SLOW transition. The 50% duty cycle produces only odd harmonics if the rate of change is VERY fast but the slower rate would produce a mix... odd and even harmonics.
I dispense with my preferred term "duty cycle" and adopt Lloyd's "closed or open quotient". If both quotients were say, 5%, then the transition times must obviously be the other 90%. In this condition the air flow rate would be distinctly triangular and therefore approximate a sine wave. This is very falsetto like except that a Fourier analysis would indicate the presence of a tiny amount of 3rd harmonic. If the closed quotient then altered so that there was NO actual closure, the 3rd harmonic would disappear and we would be left with the falsetto. Great description Lloyd.
Just musing...... Reg.
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