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Discussion in 'Trumpet Discussion' started by Sethoflagos, Mar 30, 2015.
Seth, I did not think you were a New Zealander Ducks for cover.
I am beginning to think along the lines of an energy balance, potential energy of blowing pressure and kinetic energy of air stream. as the air has to go through the mouthpiece, If I still have an unmounted thermistor (think fly spec on a 0.001 diameter wire) I shall insert in Mp back bore after the throat and make a flowmeter. Back to the books.
Thermistor would be good. Though with these rapidly fluctuating quantities, the challenge is always getting the system inertia (thermal inertia in the case of a thermistor) down low enough to track the signal without too much lag.
We could even go the whole hog and bond a mini strain gauge to the shank next to the thermistor to try and pick up a pressure signal. Even if we didn't manage great absolute accuracy, it would be really interesting to plug both signals into an oscilloscope and see what was going on with phase shift vs volume etc.
Does tongue position have any influence on air pressure?
sethoflagos & stumac will know better but I think if the tongue is raised to speed up the air (venturi tube), I think the pressure in that small area goes down (danny bernoulli).
Seth, stumac, did I get it right?
I believe the TM approved term is 'horse feathers'.
If you don't (want to) read my postings, I really cannot help you. They're not in German.
The pressure is set by the balance between the abdominal force on the lungs working against the dominant flow restriction, which is the aperture. For the tongue to affect this pressure, it must create a secondary restriction which is comparable in area to that of the aperture. It will then start to reduce the pressure available at the front of the mouth until ultimately the flow is totally blocked off. This is what we do when tonguing a note. We momentarily block off the airflow with the tongue to kill the old note with a negative pressure wave, then get it out of the way as quickly as possible to initiate a positive pressure wave which kick starts the next note.
A 'normal' tongue level will have no affect on pressure whatsoever. The flow area is a couple of orders of magnitude greater than that at the aperture.
What about the air pressure playing only the mouthpiece?
Same deal. Somewhat in defiance of Rowukian orthodoxy I was leaving the instrument out of the equation. As far as the lungs are concerned, they only really 'see' the aperture. The aperture on the other hand 'sees' both the steady(ish) driving force from the lungs (modulated by tonguing) on one side and the resonant behaviour of the instrument on the other. This obviously impacts the behaviour of the aperture, opening it up or stifling it as the case may be, and this will be different from just buzzing the mouthpiece, or free-buzzing for that matter.
What thought's lie behind the question? (And please don't say 'nothing' )
How about "curiosity" for an answer? My questions were all about using the data you've collected and ways to gather ancillary data. The first question was about the effect of changing tongue position while being measured by the manometer, the second to see if playing the same notes on the mouthpiece alone require the same pressure.