Distinguished SOTW Member, Forum Contributor 2014
Sort of, but not necessarily. As the pressure in the mouthpiece approaches neutral, the reed will open based on its particular modulus of flexibility or "stiffness" (not explained or even addressed in the text.) The stiffer the reed, the larger the pressure differential can be (not explained or even addressed in the text.) And by neutral pressure, I mean neutral as to the high pressure being produced by the player, not ambient (not explained or even addressed in the text).Consider the system without the air stream. If the pressure is higher in the mouthpiece it'll force the reed open.
The text does explain that the pressure produced by the player is high and relatively constant. That means "low pressure," as indicated in the mouthpiece diagram with the reed closed, actually means "pressure above ambient sufficient to allow the reed's stiffness to overcome the constant high pressure produced by the player." Okay, we can reason that out by ignoring the diagram. "Low pressure" in the diagram doesn't mean lowest, or even low as to ambient. Okay, ignore the diagram.
The diagram shows high pressure in the mouthpiece with the reed open, when actually we both agree that that is when the low pressure (i.e., the Bernoulli effect) occurs in the mouthpiece and pulls the reed closed. Okay, ignore the diagram. Then, the highest relative pressure in the mouthpiece occurs when the reed is closed, which allows the reed to open. Okay, ignore the diagram. Then read the text for an inartful explanation as to how the diagram is misleading and out of phase. Okay. Got it.If it is lower it'll allow the reed to close. It isn't the high pressure closing the reed. The diagram shows high pressure in the mouthpiece with the reed open. With a more open aperture, more air goes in. The air flow causes a Bernoulli effect which closes the reed.
We are in agreement. Good thing we had the diagram (to ignore), the text (to explain), and could then determine that low and high pressure terminology can be extremely complex to diagram and explain accurately. We have the proof.
I'm perfectly willing to accept that it's just me that finds the diagram less than helpful and the text less than enlightening.
Sorry about no "material" content.