Tunborough wrote: ↑Thu Jan 19, 2023 7:17 am
Very interesting. The first few of responses highlight some additional requirements... The blowing machine must be quiet enough that it doesn't interfere with pitch measurements, it must have continuously variable output over a wide range (which I do, but a hairdryer does not), and its output must be stable for long enough to take stable pitch measurements (which rules me out).
The hairdryer could be made variable by spilling some of its output, but it would still be very noisy.
What I want to do is measure the output frequency of the whistle as the flow is varied. What's the frequency at the lowest flow at which a note just speaks? What's the highest frequency just before a note jumps to the next register? What's the lowest frequency in the second register before the note drops down to the first register? How does the frequency vary with flow between these extremes? With this information, we can design a whistle that stays in tune with a regular increase in breath flow as we go up the scale.
OK, I did a little playing with this in the current setup. Tuning the whistle (by pulling out the head) so that A (xxo ooo) was at 440 in the middle of its comfortable playing range, I then looked at xxx xxx. I had previously reported that as playing OK between 8 and 10L/min, but adding the tuner meant I could now see this is quite flat, starting at about -60 cents around 10L/min, needing 12L/min for 0 cents, and breaking at +10 cents at 13 L/min. It then jumped to the 2nd partial -55 cents at 14L/min, 0 cents at around 22L/min, and breaking around +10 cents at a slightly higher pressure.
I had gone back to the single 20L/min flow meter, to maximise precision, but then found I needed to go over that. This system would benefit from easily switchable flow meters!
Oh, and I did note a high level of hysteresis - once you had performed a regime change say into the upper octave (2nd partial), you could drop the flow rate quite a long way lower before it flopped back to the fundamental regime. I think we knew that instinctively, but it was nice to see it happen "in the lab". I'd want to sort out my flow rate monitor switching before investigating that further. (Heh heh, I'd have to make sure that the flow rate monitor switch didn't drop me into the lower mode by momentarily interupting flow. I can probably leave one monitor permanently connected, and just drop the second one in parallel when I need more range.)
trill wrote: ↑Thu Jan 19, 2023 12:30 am
4) One question I have is what role the human anatomy (mouth cavity, throat, lung volume) have on the "total acoustic field".
That we don't know yet. There is something happening, because skilled recorder players have more control over frequencies around the register shift than novices.
And I imagine one of those skills is learning to exploit the hysteresis I mentioned above. A chirp of pressure will produce the regime change, you can then back off a bit to prevent going too sharp or too shrill without fear of dropping back down.