[Trombone-l] Acoustics of brass instruments

Fri Jun 2 02:08:48 CDT 2006

Several years ago we had a similar discussion.

IIRC, one of the list members (possibly Hanspeter Schmid?) was supervising a
PhD candidate trying to mathematically model the wind column.  Of course you
have to validate your model with experimental results.  In order to do this
they had to add the oral cavity area, because the data didn't work out
correctly if you just considered the column past the lips.   So yes, there
was some actual evidence we have to consider the player's physiology as
well.  

Might be worth a search through the archives.  

-----Original Message-----
From: Samuel Keyser [mailto:keyser at MIT.EDU] 
Sent: Thursday, June 01, 2006 18:54
To: Trombone-L list
Subject: Re: [Trombone-l] Acoustics of brass instruments

Fred has made my point much better than I have.  It is the multi- 
component aspect of the system that gives it its special character.   
Modeling it is not a trivial thing.  In terms of modeling the vocal tract to
account for speech, for example, all kinds of things have to be taken into
account, including sub-glottal pressure, supra-glottal pressure, the length
of the vocal tract, the compliance of its walls, just to name a few.

If we don't take the whole picture into account, we are like the blind men
touching the elephant, saying "It's a wall," "No. It's a tree," "No. It's a
rock."

Be well everyone.

Jay

On Jun 1, 2006, at 12:41 PM, Fred Hudson wrote:

> Jay makes an excellent point. In a broader sense the acoustics of 
> brass instruments, or for that matter wind instruments in general, are 
> greatly affected by the anatomy of the player. In fact, the sound 
> issuing from a trombone is the product of a multi-component system 
> beginning in the thoracic cavity of the player and ending at the bell. 
> There have been many threads on this list in which we have posted 
> attempts to analyze the effects of variation of one component without 
> taking into account the confounding effects of other variables. The 
> end results of these have understandably been non-conclusive and 
> sometimes, unfortunately, have led to some "intemperate" remarks. In 
> my opinion the way to resolve this would be to develop a mathematical 
> model, confirmed by experiment, of the system as a whole so that the 
> effects of changing one component on the other components could be 
> predicted. But this would be a gargantuan task and almost impossible 
> to model the human component given the infinite variations between us. 
> And, after all, It is the human component that becomes the receptor 
> and thus the final judge of "the right sound", which is obviously 
> subjective and not treatable analytically.
>
> There is enough empirical data on the mechanical components of the 
> system to make choices leading us to a particular sound, so when you 
> find what works for you, don't sweat the details - just relax, take a 
> deep breath and blow!
>
> my two cents worth
>
> Fred H
>
> "The most unsafe component of an automobile is the loose nut behind 
> the wheel". Your assignment, Mr. Phelps, if you choose to accept it, 
> is to find an analogy to playing a trombone.
>
>
> ----- Original Message -----
> From: "Samuel Keyser" <keyser at MIT.EDU>
> To: "Trombone-L" <trombone-l at server5.samford.edu>
> Sent: Thursday, June 01, 2006 8:57 AM
> Subject: [Trombone-l] Acoustics of brass instruments
>
>
>> In the recent thread about how brass instruments respond to noise 
>> sources created at the lips, I don't recall any mention of the vocal 
>> tract itself.  This resonances of the vocal tract are also excited by 
>> noise at the source.  The process is called "coupling."  The most 
>> likely affect of coupling in the vocal tract is to affect amplitude 
>> in the horn itself as well as certain harmonics.  My guess is that 
>> when you hear a trombone player's sound and recognize it as Trummy 
>> Young, or Dorsey, or Watrous, etc. what you are in part recognizing 
>> is the tonal cloak that coupling lays over the resonances of the 
>> horn.
>>
>> I don't know if coupling has been studied in detail.  If not, it's 
>> probably worth it.
>>
>> Jay
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