valve oil

[hnotes]

Fast Freddie, Its all technique,

THanks for putting so much work into researching this. I'm so excited to be learning this!!! Ok, since you all have a phenomenal grasp on waves, I have another question along the same lines. What determines the acoustical efficiancy of a physical amplifier. It is my understanding that a trumpet is nothing more than a fancy megaphone. How do we make it more efficient? Is there a correlation between AC tank circuits(AC voltage applied through a capacitor and inductor to get more voltage than the signal) and the trumpet?

[_Don Herman]

Joshua: You lost me a bit there... Apologies in advance, but I'm going to use layman's terms for this description here. I can understand the air velocity slowing as it passes through the air, because if you input a fixed airflow through a small aperture into a small diameter tube, then enlarge the tube as you go, the air must slow down to fill the additional volume. So, I think I follow the speed reduction. I do not follow that the actual quantity of air ("volume") is larger at the bell than the receiver -- where does the extra air come from? (Hmm, that's likely to generate a lot of responses, mostly -- get ready -- hot air! <groan now> ) Aside: what does E.I. stand for? Second aside (from your second post, to hazmat): How does turbulence add energy?

hazmat: I think the gap issue relates more to acoustics than airflow, a comment I believe applies to much of the discussion. The acoustic impedance is somewhat loosely coupled to the airflow -- related, but in fact e.g. acoustic resonance of a pipe closed at one end (like, a trumpet when you play it) is related primarily (first order) to length and temperature, not the diameter (volume) of the tube.

hnote: There are electrical analogues for acoustic impedance and other flow problems. A trumpet is a horn (duh, but I mean that in the acoustical sense of what the radiating method is) and models can be (and have been) made. As you suggest, RLC models are common for showing resonances in the structures. As for what determines the acoustical efficiency, I'd have to check back for the scientific (or engineering, at least ) answer, but do recall that a horn structure is the most efficient radiator (in coupling energy from the electrical driver to the air). And, that acoustic power conversions are among the most ruinously inefficient, along with conversion of power into radiant (light) energy. Translation: speakers, and trumpets, are pretty inefficient, and so are light bulbs. I can post my acoustics text reference after I get home -- be prepared to handle two-dimensional calculus just to get the basic equations. I hate math.

Much of this has been discussed before on TH (and TPIN and elsewhere...); a search might turn up ome good stuff. I looked for but haven't yet found a thread which spun off an Adam's leadpipe topic (I think) and resulted in a very fine analysis (not mine, btw).

My 0.000001 cent (microcent) - Don
_________________
Don Herman/Monument, CO
"After silence, that which best expresses the inexpressible, is music." - Aldous Huxley

[It's All Technique]

What has always surprised me, is all the acoustical theory I've read on how a trumpet works, never has any discussion on fluid flow. Yet, features in a trumpet appear to be there because. . . of fluid flow! If I abide by the strict acoustic impedence explanation of trumpet performance, then reverse lead piping, round verses squared off tuning slides, properly aligned valving should make no difference in the performance of the instrument. The acoustic wavefront travels down the walls of the instrument oblivious to that solder ball in the joint. Of course these features do have dramatic impact on the performance of a trumpet, and people pay a lot of money for them.

I guess I have a hard time making the connection for these design features, and explaining why their there using traditional acoustic impedence theory. Let's take a step back, for a moment, and think about fluid dynamics. WHOA! Now these features make a lot of sense! Reduction of friction, elimination of sudden constrictions in the line, basically anything you can do to make that fluid get from point "A" to point "B" with the minuimum of effort.

I'm not attempting to rewrite acoustic theory here (that's been proven for over a hundred years), but if we take a "Leap of Faith" and say "Fluid flow is a factor, and is important." it might take you into some interesting design directions.

I firmly believe that trumpets look the way they do because . . well . . they are partly meant to, lets just call it tradition. If I wanted to design a horn for perfect fluid flow I certainly wouldn't make the 1st, 2nd, and 3rd slides with 1/2" radii. I wouldn't create the tortured paths through the valve housings. But if I fixed all that . . . it wouldn't look like a trumpet!
_________________
Eric

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[Fast Freddy]

hnotes,

Eric deserves the credit on the actual "research".... I simply made an educated guess. As a mechanical engineer who owns a company which designs, develops and manufactures turbine engine componentry... not to mention being an avid trumpet player, I hate to say this but... I have never really thought much about what actually happens when we pick up the horn to play a note. Being an engineer can be a curse in many ways, especially when it comes to over-examining things. I have not found good results with this where trumpet playing is concerned.

The article Joshua refered to is a short one but one good point to ponder is as follows....

Depending upon the pitch and volume played, the player's breath exits the trumpet as a laminar or a turbulent jet. A low-pitched note played softly generates a laminar jet, while any loud note and almost any high-pitched note, creates a turbulent flow. Thus, the trumpet has a unique way of producing some common fluid flow phenomena

From that I would suspect that both laminar and turbulent flow exist, not to mention the difficulty in predicting the type of flow produced in that transition region where Re falls between 2100 and 4000. Now consider that average density is dependent on average pressure, so we should work towards calculating an Re based on constant mass flow per unit area. If we are talking about playing in all registers at all dynamic levels (typical trumpet playing) then you have a system that is very dynamic. Like I said before, it would be error in assuming that turbulent flow governs every aspect of fluid flow through a trumpet. It is obviously much more complicated than that, which makes this very interesting indeed!

I can't touch Don's queries into shock wave production, not my area of expertise at all. Give me something mechanical.

On that note I'm in total agreement with Eric on traditional trumpet design. A "better" design (again just postulating) would definitely be something much different looking than the norm. Not only would we want very large flowing paths of equal section area, we would want to reduce loss coefficients at every junction. Rounded entrances and exits, anything that will aid in pressure recovery throughout the system.

Too bad there isn't more scientific research in this area. With the right group of people engineering, developing mathematical models, etc., I don't doubt something "unique" could be developed with todays technology.

Take care!



[ This Message was edited by: Fast Freddy on 2003-11-21 22:14 ]

[West-Coast-Horns]

As far as using oil to possibly fill in any pits in the metal in the horn, I heard a while back of an old practice (50's 60's) of soaking new horns in milk for a day or two to fill in any gaps. I'm not sure how truthful that is, but I was wondering if anyone has ever heard of that.

[_Don Herman]

Eric: I am basing my assumptions about the impact solder bumps etc. in the tubes have on sound waves on acoustical theory relating to (primarily) sound transmission and horn (speaker) theory. Any bumps, bends, etc. have some effect on the acoustic impedance and transmission coefficients. I suppose a good analogy is to transmission line theory -- every little bump, restriction, bend, expansion, etc. will introduce an impedance discontinuity. In fact, the transmission line and waveguide theory class was the prerequisite to the aforementioned graduate acoustics class. Makes my head hurt.

I'd love to have a program which performs FEA or similar on sound waves in tubes -- be a great way to spend some hours! Anybody for implementing the equations in Matlab or Mathcad? I keep thinking about it, but haven't found the time yet...

See ya' - Don
_________________
Don Herman/Monument, CO
"After silence, that which best expresses the inexpressible, is music." - Aldous Huxley

[farmbrass]

OK then:

I what ways would laminar flow trumpet sound different from a turbulent flow trumpet.
(How does cross sectional velocity variation affect frequency spectra, if at all)

I have my ideas, but I'd like to hear your's first.

Keith ( I have degrees in fluid mechanics, but that really doesn't mean s**t ) H.

[Fast Freddy]

[hnotes]

Is there any way we can compare a capacitor and an inductor to a tube? I guess what I'm getting at is that cap., and ind., are two seperate components. can those be compared to length of tube and taper?

[farmbrass]

Well it is not so much that my education has been a waste, it is just that I've learned that when it comes to fluid flow, intuition even if you completely understand the governing mathematical equations, usually is of little help in analyzing complex behaviors such as what we're talking about here. Mathematical analysis and/or computer modeling of the fluid equations and wave equations usually give a great deal of personal satisfaction but, still, often poor results. It is usually far more informative (and fun) to set up real-world tests with anemometers, pressure transducers, scopes, spectrum analyzers, etc. I think this is what Schilke did when learning how to build trumpets.

That said, ya still gotta start somewhere and that is with your best guess: To answer my question: I think that laminar flow with it's greater cross-sectional velocity variation (perpendicular to the flow axis), will tend to smudge the harmonics a bit. As the pressure wave traverse the tube, the wave will move with and against the flow of the air in the tube. The wave is moving at about 1100 fps, the speed of sound. The flow will range from between 0 at the tube wall (boundary condition) and about 6fps in the center of the tube, based on previously published volume rate measurements. In the mouthpiece the flow will be substantially faster. Because of the velocity variation across the tube cross section the wavefront will be deformed laterally , resulting is a small frequency spread of from the center of the tone. Turbulent flow will have a very small boundary layer- the velocity across the tube is more consistent, so a horn with turbulent flow, all other things equal, will have harmonics with less fuzz. More pure tones. That said, I would expect the frequency shift to be about 0.5% with laminar flow in the leadpipe.
I also think that if a trumpt emitted nothing but multiple harmonic pure tones, it would sound pretty awful. So some of the bends, and obstructions may actually help "color: the sound in a positive way.

I would also think that blobs in the pipe will tend to reflect portions of the sound wave, resulting in small amplitude higher frequency spikes in the frequency spectrum. Adfing more "color" to the sound.

That is my semi-educated guess. I estimate I have about about a 50% chance of being right.

Keith

[_Don Herman]

On 2003-11-22 15:42, hnotes wrote:
Is there any way we can compare a capacitor and an inductor to a tube? I guess what I'm getting at is that cap., and ind., are two seperate components. can those be compared to length of tube and taper?

The resonant frequency of the tube can be modeled with an LC network, but it's not an infinite Q system and so you have to add some R as well. The actual situation gets pretty ugly pretty quick, as all these little bends and tapers being discussed add elements to your model...

If anybody's interested, John Lynch (not the mpc guy, a physicist who likes repairing trumpets and does a very fine job on 'em) posted trumpet spectra here: http://www.whc.net/rjones/jlynch/index.html

(Aside: Ralph keeps the ITG links hub as well, and has a simply amazing link collection on his personal site!)

Schilke is famous for having worked with mathematicians to tweak the nodes in his horns... I think the Schilke Loyalist site has a paper or two on that. Seems like the leadpipe has 21 little "bumps" in it, indetectable by eye, which affect resonances to dial in the response.

FWIW - Don
_________________
Don Herman/Monument, CO
"After silence, that which best expresses the inexpressible, is music." - Aldous Huxley

[hnotes]

Every one think back to when they were first developing their upper register. Did anyone remember feeling a break or vibrational change around high eb and then above double ab? For me it felt as if high eb up to ab were almost the same notes. Then there seemed to be another break but once over that a up to double d feel like the same note. Is this due to the laminar/turbulent flow that we have been discussing?

[Big Phat Jan]

I've heard about soaking horns (not trumpets) in milk. I know at least 2 people that do it, but I can't remember why. I do remember one of them saying that it means you HAVE to practice every day or it everything goes all screwy. So don't put milk down your trumpet

[farmbrass]

Hey Hnotes,


Look at he spectral plots and read the analysis at the link provided by Don Herman. This is a really nice site. Your question will be answered by looking at "The natural Resonances of a Trumpet" page.

I think those milk soaked trumpets would be full of sour notes. Isn't milk acidic?

Actually, I think the air flow in a trumpet has very little to do with the way it sounds. It is more a function of the sound-wave behavior (the physical dimensions of the acoustical waveguide (the tube) of the trumpet, along the with the various resonating modes in the metal, and the complex interaction of the mouthpiece shape, lip behavior, etc. etc. It is a fun subject worthy of study, and has been extensively studied. There is a great PHd Thesis by David Berners, July 1999, Stanford. Maybe you can find it on the Stanford web site. My guess is they'll sell it to you for a fee. There are about 20 pages of Matlab code included.

http://www-ccrma.stanford.edu/overview/publications.html

Berners, D. (1999).
Acoustics and Signal Processing Techniques for Physical Modeling of Brass Instruments.
Ph.D. thesis, Dept. of Electrical Engineering, Stanford University.
Available as Stanford University Department of Music Technical Report STAN-M-105 ($14.00).


Now, I'd better practice and see if I can figure out how to play above high D.


Keith


I found it on the Mr. Berners website:

http://ccrma-www.stanford.edu/~dpberner/pubs.html

also

http://www-ccrma.stanford.edu/~dpberner/downloads.html

<font size=-2>[ This Message was edited by: farmbrass on 2003-11-23 12:38 ]</font>

[hnotes]

A while back I saw this product called an acousta coil. I'm sure you all have seen it. I think he tried to explain it like ripples in a pond or something. Do you know if there have been any test done on them? Similare to what Mr. Lynch set up? That site was interestin and informative.

[hnotes]

sorry about my texas typing on the last one. "interesting" is what I meant to type

[bent trumpet]

I just received a bottle of the Bell's Super Lube, and have been using it for a couple of days. I love this stuff. It seems, so far, to work better than anything else I have tried, and I love the mist applicator.

[_dcstep]

When cleaning my horn earlier today, I noticed that when I poor water into the bell, it comes spinning out the leadpipe. Is this of any interest in this discussion of waves and laminar flow?

Dave
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[rafterman]

What? Huh? Where am I?

The point about seatbelts is....no, wrong thread. Valve oil, turbulance, laminar flow?? Right... !! I must have fallen asleep. Technical writting always does that to me. (Smiley Face here)

As a liberal arts guy, I don't have much to say. When it comes to physics and engineering, I'm a man of faith. Does this site offer anything to the discussion on trumpet physics?

http://www.geocities.com/Vienna/3941/index.html