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....its the same thing if you put your hand in the bell of a trumpet,trombone or use your knee to get the low A on tenor i forget where i have this video,but its bugle blues...the guy plays really great blues trumpet on a bugle using his hand in the bell....
 

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I don't know the answer, but check back often. As soon as the acoustic guys get here, the thread will go up for grabs, and get shut down in a heartbeat!
 

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What a great question! There is very little mentioned about this in the literature I have. Benade in Fundamentals of Musical Acoustics p. 427 compares the lowering of pitch of the french horn by the player inserting the hand in the bell to placing a tube up to one's ear and slowly covering the open end of the tube. Restricting the opening lowers the natural resonant frequency of the tubing. On the saxophone it is this lowered natural resonant frequency that tells the reed at what pitch to vibrate.

Let the games begin.

:bsod: :violent1: :boxing: :director: :banghead: :angry4: :protest: :argue:

:popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :popcorn:
 

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The open end of the neck is a displacement anti-node. Reducing the diameter of the bore at the opening will lower the pitch of all resonance modes. Increasing the diameter will raise them. Even though you shorten the length, which raises the pitch, the reduced opening diameter effects pitch even more in the opposite direction.

The mouthpiece end is a compression anti-node. The effects of reducing/increasing diameter are opposite those described above. Reducing raises pitch. Enlarging lowers it.
 

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The physical opening "diameter" does not change. The volume of air in the end of the tube is reduced by the insertion of the finger. That raises the question of whether reducing the volume has the same net effect as reducing the diameter. There is another acoustic effect at play here as well. When one puts the hand closer to the opening while playing the neck the pitch drops as well even though there is nothing inside the end of the neck to reduce its volume. This I suppose is caused by the hand restricting the vibrations in the area of its end correction.

I am just now experimenting with my alto neck and a small piece of blu-tack.

Blu-tack in the tenon opening - the pitch lowers about 1/2 step
Blu-tack about halfway in the neck - the pitch lowers slightly
Blu-tack in the small end - no pitch change
 

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Discussion Starter #10
Little help with the basic physics: when a compression wave changes phase by 180 degrees, it is essentially in phase with the original wave, is that correct? This is unlike a transverse wave, wherein two waves with 180 degree phase difference would nullify the signal, right? And therefore a 90 or 270 degree change in phase in compression waves would nullify the signal?

EDIT: I see that my assumption about the transverse waves is incorrect. Why? If the "ideal" reflected wave has the same amplitude as the original, but hits its perigee at the same time as the original hits its apogee, the energy should cancel itself out, right?
 

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The physical opening "diameter" does not change. The volume of air in the end of the tube is reduced by the insertion of the finger.
I need only cover 1/2 the neck opening with a 0.0015" thin sheet of paper for the pitch to drop approximately the same amount as when I cover 1/2 the opening with my much thicker finger. Is this effect because of reduced volume (equal to that of the very thin paper blocking the opening) or a reduced opening diameter (cross-sectional area)?
 

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Little help with the basic physics: when a compression wave changes phase by 180 degrees, it is essentially in phase with the original wave, is that correct? This is unlike a transverse wave, wherein two waves with 180 degree phase difference would nullify the signal, right? And therefore a 90 or 270 degree change in phase in compression waves would nullify the signal?

EDIT: I see that my assumption about the transverse waves is incorrect. Why? If the "ideal" reflected wave has the same amplitude as the original, but hits its perigee at the same time as the original hits its apogee, the energy should cancel itself out, right?
The standing wave is the result of adding the amplitudes of the opposing traveling waves. Where they are 180 deg. out of phase and equal in amplitude, they cancel each other out.
 

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I need only cover 1/2 the neck opening with a 0.0015" thin sheet of paper for the pitch to drop approximately the same amount as when I cover 1/2 the opening with my much thicker finger. Is this effect because of reduced volume (equal to that of the very thin paper blocking the opening) or a reduced opening diameter (cross-sectional area)?
Inserting a finger or a pencil into the center of the neck opening without touching the sides does not "cover" a portion of the opening. It reduces the volume inside. This is the way I was lowering the pitch, not by covering a portion of the end.
 

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Inserting a finger or a pencil into the center of the neck opening without touching the sides does not "cover" a portion of the opening. It reduces the volume inside. This is the way I was lowering the pitch, not by covering a portion of the end.
That doesn't answer my question. If it is volume that determines the pitch, then the thin paper should not have much affect at all, yet it does. Can you explain?
 

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That doesn't answer my question. If it is volume that determines the pitch, then the thin paper should not have much affect at all, yet it does. Can you explain?
I think it is about the area of the opening, isn't it? But in relation to the cross-sectional area of the rest of the bore. The part with your finger in it still counts as length, just length of much narrower "diameter".
 

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I think it is about the area of the opening, isn't it? But in relation to the cross-sectional area of the rest of the bore. The part with your finger in it still counts as length, just length of much narrower "diameter".
That seems to be in good agreement with the experts' publications.
 

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Im a little lost to the question itself, Dan are you asking about a trombone or a sax neck, Im lost by your refernece neck trombone, or are you just referring to simply a non valved trombone. Im trying to picture what it is that your doing first before throwing my couple of cents in
 

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Hmm, the question reminds me of the thread about how cold weather affects pitch, so in the same spirit...

It stands to reason that your finger warms the air at the end of the tube causing the pitch to go down. No wait, the air particles are moving faster in warm air, so scratch that.

The reason the pitch goes down must be that the air molecules bump into your finger and then into each other, confusing them. The molecules become unorganized, impeding their proper alignment. The chaos causes the pitch to go down. Yeah, that's it.
 

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Discussion Starter #20
Im a little lost to the question itself, Dan are you asking about a trombone or a sax neck, Im lost by your refernece neck trombone, or are you just referring to simply a non valved trombone. Im trying to picture what it is that your doing first before throwing my couple of cents in
Well, trombones don't have necks, so... LOL When you take a sax neck and mouthpiece and push your finger in the end like you're goosing it while you play, it sounds like a trombone slide going down.
 
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