I have read that the longer the whistle the lower the pitch and the shorter the whistle the higher the pitch.
But there are other factors. Pressure, size of the inlet, size of the outlet, diameter of the whistle... what changes occur to the whistle when these variables are changed?
More importantly, is there a way to change the threshold of when the whistle starts making noise?
For example: I want a whistle that only makes noise between 1 and 2 pounds per sqft of pressure. Outside that range it is quiet. Is it possible?
The source of the 20 mph airflow is after the whistle and increases in pressure over time, 30+ days, so when the pressure goes beyond a specific point, I'd like a whistle so I can hear it. What variables need to be considered when designing a whistle that can do this? And how would you do this?