Quote:
Originally Posted by NickD  Great thoughts here. I think it is even more complicated than we thought.
The idea of a resonanting chamber behind a speaker (think Bose speakers, or ANY speaker cabinet for that matter) affecting the behavior of a speaker is solid, but we have to consider the mass of the speaker cone.
There is a reasonable impedance match between the chamber behind the speaker and the the cone, so the effect of the chamber is perceivable.
However, the mass of the lips is pretty high compared to the mass of air in the oral cavity. There is a huge impedance mismatch.
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Nick,
I am not talking about the cabinet behind the cone on a free air speaker like Bose, AR, Polk or whatever. I am talking about reactance annulling of a speaker with a horn in front of it. In that case we have to take into account the pressure on both sides of the lips. The closer they are to one another, the less muscle that we need to keep the chops from falling into the cup. The chamber (oral cavity) can provide that variable reactance. This is why players can also use extremely shallow mouthpieces and not have their chops block the cup!
Also of interest to you would be the effect of that chamber as a low pass filter. The larger the chamber, the less high frequencies are passed. That would translate to high tongue position = bright sound, low tongue = darker sound, something we all experience! This only works because we are talking about AC not DC.
The efficiency that I mention is another aspect. Trumpets amplify most in their lower 2 1/2 octaves. That is based on the horn shape, length and bell to leadpipe size. Above that, the horn is significantly less efficient. Raising our tongue for higher notes increases efficiency making the overall response more even.
In calculating the lip mass, we have to estimate how much of the lip is really moving. The lips do not vibrate like a guitar string, they open and close like a switch. Once the standing wave is set up, I suspect the moving mass is quite low. The rest of the lip only acts like the "suspension" or butyl surround on a loudspeaker.
I guess the bottom line is that there is no "fast air". There is just the battle of air pressure in front of and behind the lips. That is easily backed up with the numbers, however complex. I have glued a little loudspeaker to a mouthpiece and let it play buzzing noises. The trumpet amplifies just like when it is being played with only the resonant node frequencies being the peaks. No air really has to "flow" at all, except to get our lips moving.