Why raw brass?

[windshieldbug]

[SplatterTone]

The high frequencies are easiest, and the low frequencies nearly impossible.

Granted the point is moot -- which is what I have been saying, or so I thought. The last post was one of those "let's suppose there is merit to the claim that more vibration leads to more high frequencies and see where it leads."

However, if you want to open another can of worms...

As one who used to sell HiFi in the sound rooms common in the 70s, I can tell you bass frequencies are very easily and very effectively damped by the woofers in the other speakers in the sound room. As one who plays tuba, I can tell you there is a vast difference in bass response in the different rooms in which I play -- far more than any difference in high frequencies. In a resonant church nave, the 32-foot C sounds nice and full. In a dead nave, about all one hears for that note is harmonics; i.e. the low frequencies are what get clobbered. Anticipating a possible response to that, I'll add that the acoustically dead nave is larger, so it isn't some obscure issue with wave lengths.

It has been too long since I did any reading on organ design. But my foggy recollection is that distance is the killer of high frequencies, while building materials and stuff in the room determine the death of low frequencies. For example, a hard stone wall will reflect bass, while flimsy drywall will absorb it. I'm sure if Robert Coulter is around, he can confirm this or set things straight. And I'm sure there is overlap in what kills high and low frequencies.

Although "impedence" is a cool term, I don't think "impedence" fits the situation. If the idea was to imply resonance follows from impedence characteristics, I'm doubtful we are dealing a resonance situation here.

Perhaps my post was too terse. So .... Going back to the claim that more vibration implies brighter sound: Vibrating brass can only absorb energy from the sound that makes it vibrate. If there were any way for it to increase the sound energy through some kind of positive feedback, then we have just witnessed the long sought after perpetual motion machine -- until the intensity of the vibration reaches the point that the horn distorts or fractures and kills the positive feedback. I don't dispute the claim that more vibration leads to a brighter tone. In fact, I'm inclined to agree with it. My skepticism is that a thin layer of lacquer is enough to make a difference. But assuming it did, given that physices requires that the vibrating brass can only absorb sound, if the sound is brighter, then it cannot be because the vibrating brass added high frequency content. This leads to only one possible conclusion: The vibration must have subtracted low frequency content.

So, if one supposes (which I don't) lacquer makes an audible difference in brightness of the tone, and one was fixing to strip the lacquer to get a brighter tone by causing the horn to absorb lower frequencies, would it not be a lot less trouble and less waste of sound energy to just use a shallower mouthpiece?

(and let years of wear remove the lacquer)

[iiipopes]

Stripping lacquer does not increase the highs by causing the horn to absorb lower frequencies. Quite the opposite. In a small way, if there are any noticable higher harmonics that seem damped by the lacquer, it's because the lacquer is a damping agent. To lacquer a brass instrument is really no different than throwing a towel over the bell, just to a much smaller degree.

I am by no means anything but a rank hobbiest, but having worked with pipe organ techs in repairs and tunings on several organs, from small to large, neo-baroque to large theatre, tracker, direct electric and electro-pneumatic, in its own case to shoved in a chamber, etc., and being on several pipe organ committees, researching this stuff to indulge my own curiosity, and as an alumnus writing a paper to my undergrad administration about the historical significance of the organ in their chapel, which the president of the college used to establish an endowment for its maintenance, I do have some definite opinions on the subject.

Regarding pipe organs and bass notes, frequency response of a room is one of those subjects that even those with graduate degrees in the field can disagree. But there are a couple of items: to hear the fundamental of any particular pitch, the room needs to be long enough so not only can the actual fundamental develop, but of a proportional size that there is no standing wave caused canceling out the pitch at any particular point. These two factors are what are perceived as the bass dropping out below a certain frequency. Second, it is the interaction of the harmonics with the fundamental that give the impression of the expanse of the sound. The fundamental is still there in a non-reverberant room of a large enough size. It's just that the rest of the frequencies that help reinforce it may not be. Over the past year the church I attend, among other additions and remodelings, took all the carpet up off the floor of its carpenter gothic nave, restored the hardwood floors with only a runner down the aisle to silence footfalls, and restored the plaster and lathe work on the walls to a good hard smooth surface (it had cracked and had been painted). Before, with a full church, sometimes it was difficult to hear the organ in the very back to lead the congregation. Now, there is no problem. The lowest bass, which is only a 16 ft medium large scaled bourdon, is still there in relatively the same amount. It is the octave above that and all the overtones that before hand seemed insufficient because they were soaked up by the carpet, that are now knitting together in the improved acoustics, which actually also tend to reinforce the bass through difference tones as well as the sparkle of additive tones, that are making the difference.

[Rick Denney]

...If there were any way for it to increase the sound energy through some kind of positive feedback, then we have just witnessed the long sought after perpetual motion machine -- until the intensity of the vibration reaches the point that the horn distorts or fractures and kills the positive feedback.

Actually, it is a resonance situation, and resonance can create excursions beyond the apparent input power. Many a radio transmitter has died at the hands of unanticipated resonance outside its intended frequency band. They call it parasitic oscillation.

If resonance didn't cause tremendous amplification of power, the tuba sound would be no louder than the buzz. We know that's not the case.

If the inductive and capacitive reactance is the same, and if the Q is very high (i.e., the simple resistance very low), then the voltages bouncing back and forth between the inductor and capacity at the resonant frequency can amplify beyond the ability of the equipment to withstand those voltages. Equipment is designed to prevent this by lowering the Q of resonant circuits (i.e., damping) or by filtering out any sources for those frequencies, or both.

If you excite the body of a tuba, it will resonate on a variety of frequencies, If it didn't, all you would hear is an immediately damped thud. Even an unmusical clang that takes a while to attenuate indicates resonance. When you coat the material with a damping material, you lower the Q of the resonance of some of those frequencies and damp some of them out. The clang will be muffled, which means that its highest frequency resonances are the ones being damped out. I've actually tried this experiment and reported about it hear (partly as a joke--my damping material was Scotch tape).

Your point is what in the sound energy produces those frequencies? I think all you need to do is look at the spectral content of a free buzz to realize just how much high frequency information gets filtered out by the tuba. It's filtered by the resonances in the air column, of course, and not by the lacquer; on that we agree.

Rick "now, back to work" Denney

[pierso20]

sir, i didn't understand a word you just said....

haha...very good answer. I unfortunately do not usually take the science approach...I take the fun approach........ not that I know what that approach really is....hmmm

[windshieldbug]

Now if you could build a solid lacquer tuba plated with brass, THEN you'd be onto something! ...

[Donn]

The difference is that the brass lacquer will damp some of that energy instead of the brass radiating it.

Has anyone ever built a tuba out of solid lacquer to test the implied thesis that lacquer has a "dampening" effect?...

...or what if a solid lacquer tuba is less resonant that a solid brass tuba, but WHEN LACQUER IS APPLIED TO THE SURFACE of a brass tuba, it actually increases the resonance...??

For me, "lacquer will damp some of that energy" does not assert or imply that a lacquered tuba will have a significantly less energetic sound.

The actual assertion can be more conveniently tested on a small sheet of brass - harmonica reed? The implication for tuba still depends on a couple of other theses: that the tuba depends to any noticeable degree on sound propagated in this manner, and that the effect in question applies to a noticeable degree to frequencies important to the tuba's sound. My guess is that both theses are false, but the fiberglass tuba is the closest I know of to empirical evidence.

[tofu]

Wouldn't having a hand on the surface of a tuba while playing have more of a dampening impact on the vibration of the horn than the finish?

[windshieldbug]

Wouldn't having a hand on the surface of a tuba while playing have more of a dampening impact on the vibration of the horn than the finish?

Only if you have a hand that can cover all the surface area, like say, uh, LACQUER!

[Rick Denney]

Has anyone ever built a tuba out of solid lacquer to test the implied thesis that lacquer has a "dampening" effect?...

...or what if a solid lacquer tuba is less resonant that a solid brass tuba, but WHEN LACQUER IS APPLIED TO THE SURFACE of a brass tuba, it actually increases the resonance...??

bloke "Play for me, please - in less than ten seconds, in F# harmonic minor scale in three octaves -accending and descending - and in thirds...first unlacquered, then lacquered, then unlacquered again."

Lacquer only has a dampening effect when first applied.

Oh, you mean damping.

You make a good point. Scotch tape has a damping effect--I have the measurements to prove it.

But I don't know how elastic baked cellulose or epoxy lacquer is. I suspect it's pretty elastic, though not very flexible (epoxy is more flexible than the cellulose stuff). And it could be as elastic as the brass.

If so, then it should not have much damping effect as a result of hysteresis, which is what made the Scotch tape do its thing. The tape's adhesive probably contributed more damping than the tape itself, too.

Hysteresis is the absorption of energy during repeated strain cycles. Tires get hot because of hysteresis, etc.

If it doesn't contribute much damping because of hysteresis, then the only way it can change the resonance of the brass is by adding mass or stiffness. Thus, it should have the same effect as somewhat thicker brass. I'm quite sure the lacquer is considerably less dense than the brass, so a given thickness will add much less mass than the same thickness of brass.

Rock "who wonders at the weight of lacquer" Donnor

[Rick Denney]

Wouldn't having a hand on the surface of a tuba while playing have more of a dampening impact on the vibration of the horn than the finish?

Only if you sweat a lot.

Oh, you mean damping.

The tuba touches our body in several places, and not much provides more damping than a balloon full of jello.

I think but the brass can ring in the parts that are far from those contact points, because the ring attenuates out before it gets to those spots anyway. Some frequencies are affected more than others. I once noticed a surprisingly large resonance in a King 1241 at about 100 Hz. You could strike the upper bow of the tuba with the flat of the left hand and feel it vibrate for several seconds in the right hand and legs. The jello water balloon didn't damp that out that much.

Rick "who thinks the lacquer has no real effect" Denney

[Rick Denney]

[
Rick "who thinks the lacquer has no real effect" Denney

If a modification to read "no real effect of significance" is acceptable I wholeheartedly agree in the case of tubas.

For me, real = significant.

Rick "if you can't sense it, is it real?" Denney

[windshieldbug]

Posted by Rick Denney on August 19, 2001 at 00:21:28:

In Reply to: Re: Re: Re: Vibration, damping, and weight posted by Laurence on August 18, 2001 at 10:27:20:

I'm quite confident when I say that it won't affect the stiffness. But I'm not at all confident that it won't affect the sound.

For me, real = significant.

Rick "if you can't sense it, is it real?" Denney

No wonder we have traffic jams.

No wonder we have posting jams...

[SplatterTone]

If resonance didn't cause tremendous amplification of power, the tuba sound would be no louder than the buzz. We know that's not the case.

There is no amplification. The term is acoustic coupling. It relates to the efficiency of the transfer of energy. Amplification would violate laws of physics. It's the same principle that is behind horn loaded speakers. Take a small speaker and play some music through it with a one-watt amplifier, and you won't get much. Put that speaker at the small end of a concrete exponential horn that extends halfway down the block and opens up the size of your living room wall, and you will get ear-crushing volume. We should note that knocking on the concrete horn will get you that dull thud you mentioned later. And horns on horn loaded speakers tend to be rigid and produce a sound only slightly this side of a dull thud when knocked on.

If you excite the body of a tuba, it will resonate on a variety of frequencies, If it didn't, all you would hear is an immediately damped thud.

I'll emphasize your use of the word "variety", as in a whole lot. In fact it is broad spectrum, and varies throughout the tuba body. High Q and broad spectrum don't usually go together, which is the basis for my minimizing the role of resonance of the metal. I will certainly agree that as one travels through the tubing of the horn, the wall at any given point is more sympathetic to some list of frequencies. But this constantly varies throughout the horn, so I'll submit that it is a stretch to refer to the metal of the horn as a resonant body.

Of vastly more consequence is the resonance of the air column inside the horn. That is our resonant entity.

Even an unmusical clang that takes a while to attenuate indicates resonance. When you coat the material with a damping material, you lower the Q of the resonance of some of those frequencies and damp some of them out. The clang will be muffled, which means that its highest frequency resonances are the ones being damped out.

If the tuba were played by banging on it, you might have a point here. Any vibration in the tuba metal comes not from directly exciting the metal by banging on it, but by stealing energy from the air column. More vibration means more energy being taken. Less vibration mean less energy taken. Refer to my previous comment about the concrete exponential horn. If a concrete tuba could be built, it would respond to your knock with a dull thud. But (assuming the interior is smooth) I am quite sure that high frequencies would come sailing out of the bell in fine style; and low frequencies would be amazing.

Your point is what in the sound energy produces those frequencies?

That was not my point at all. My point was very simple -- we're talking physics 101, first semester. The brass gets it energy by removing energy from the vibrating air column. Which means less energy is left in the air column. Which means the vibrating brass can't selectively add to anything; it can only take away.

I think your points are entirely related to producing sound by banging on the brass. Although in moments of frustration, I might have been tempted to do this, thus far any sound produced this way on my tubas was accidental, and tonal quality of the sound produced in this manner was not my primary concern.

[Art Hovey]

Splattertone has got it completely right.

In an earlier post I remarked that it's the player who determines the sound of the instrument, not the finish. I did not mean to imply that a player can make a crappy small tuba sound like the CSO York. What I meant was that a good player can make two otherwise-identical tubas with different finishes sound alike. Or if he chooses to he can make them sound very different.

Differences attributable to the finish will always be insignificant compared to the changes in sound that can be created by the player.

And let's not forget the dampening effect of the plastic tubing that many of us affix to the rim of the bell. That has a much greater effect on the way my Yorkofone bell vibrates than any lacquer ever could. It also enables me to put the horn down on a rough surface without scratching anything.

[windshieldbug]

And let's not forget the dampening effect of the plastic tubing that many of us affix to the rim of the bell. That has a much greater effect on the way my Yorkofone bell vibrates than any lacquer ever could. It also enables me to put the horn down on a rough surface without scratching anything.

Whereas I put my so unadorned bell down almost everywhere, and enjoy the ringing sound that the reduced mass of the bell resounds with...

[Todd S. Malicoate]

a good player can make two otherwise-identical tubas with different finishes sound alike. Or if he chooses to he can make them sound very different.

And therein lies the problem with testing theories about lacquered/unlacquered tubas, at least until a robot tuba player, who plays in the exactly same way every time, is invented.

Todd S. "who thinks this topic really boils down to (in the minds of many Tubenetters)
...unlacquered = more resonant = better = winning a job = why bother practicing" Malicoate

[windshieldbug]

Why raw brass?

More nutrients than steamed brass.

[tubamirum]

When lacquer is stripped the player can tell something is different but not the audience. The effect is more noticable on large intstruments than small ( i.e. tubas vs tpts)

[SplatterTone]

... the player can tell something is different but not the audience. The effect is more noticable on large ...

Especially true of big, manly tuba players wearing women's underwear.

Don't you think my tone has a lovely silky quality tonight?