[Trombone-l] Leadpipe

[Jeff Albert]

I can't believe I am about to get suckered into one of these  
discussions with Tim, but here goes.

On May 25, 2006, at 8:41 AM, Richardson, Timothy Mr. DAC USAG  
Franconia DPW wrote:
>
>
> The second part, function, is potentially debatable.  True, air is  
> a fluid.
> But the purpose of the leadpipe is not to affect the flow or  
> pressure of the
> air/fluid. (Unlike the purpose of a venturi in every application I  
> know of.)
> In fact, air flow through the horn isn't technically even necessary.

Not true.  Lips do not buzz without airflow.  The leadpipe does  
affect the flow or pressure of the air leaving the buzz.  That is why  
changing leadpipes will change the way a horn blows.  It influences  
the system of air movement from the mouth through the buzzing lips  
and into the trombone.

> The
> purpose of the leadpipe is to affect the sound wave, which is NOT a  
> fluid.
> The leadpipe provides a transition from the smaller mouthpiece to  
> the larger
> slide tube, but for the sound wave, not the air flow.

No, it is the air.  Use a different sound source, like your vocal  
chords.  Hum into a trombone.  Take the leadpipe out and hum into it  
again.  There is no perceptible difference.  The reason different  
leadpipes can affect the sound is due to  their influence on the  
embouchure system, via air flow/pressure changes.

>
> While the primary purpose of the leadpipe is control of sound wave,  
> I will
> admit it does offer some flow resistance.  My estimate is somewhere  
> between
> 1/15 and 1/20th of the total trombone airflow resistance is found  
> in the
> leadpipe section.

What is that based on?  My experience would lead me to believe that  
as much as half of the resistance characteristics of a trombone come  
from the mouthpiece/leadpipe system.

Jeff