Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] sound



Perhaps this is just a question of interpreting that equation.

It might be clearer to write it this way:
f(n) = n*v/(2*L)
where:
n is a positive integer
v is the speed of sound
L is the length of the pipe
f(n) gives you a list of resonant frequencies

As Don points out, you change your embouchure to adjust the driving frequency of your lips. Only when this driving frequency matches one of the resonant frequencies of the pipe will it produce a good sound. There is some feedback from the sound in the pipe which helps to lock in the frequency of your lips. That is to say, you feel your lips buzz against the air column and that helps to cause the flapping of your lips to match a resonant frequency of the pipe.

Paul


On Apr 12, 2013, at 10:14 AM, "Anthony Lapinski" <Anthony_Lapinski@pds.org> wrote:

Thanks for these responses. So what, then, changes in the equation fn =
nv/2L? Lips vibrate faster, so v changes? But I thought v = 343 m/s (speed
of sound in air). Or does n change, which creates the higher
frequencies/harmonics? What changes in that equation to predict which
frequencies are played on a bugle or other instrument where L is constant)?

P.S. I was a big fan of Maynard Ferguson, who could hit super high notes
on the trumpet. Saw him live in concert serveal times. Amazing!


Phys-L@Phys-L.org writes:
Paul Nord on 4/12/13 at 9:16 am wrote:

" Yes, just as you suspect, there are multiple resonances in the bugle.
The
resonance which sounds is a function of the driving frequency. This means
that such an instrument can only play certain notes of the scale. There
may
be a small range around those pitches which will sound. But, principally
you are limited to those notes because of the fixed length of the
instrument. On a valved brass instrument like a trumpet the valves cut
off
or add lengths of pipe. Each valve position allows a different harmonic
series to sound."

As an old (high school level) trumpet player I can assure you that the
player's lips must vibrate at a higher frequency to achieve higher notes
on
a bugle. A trumpet becomes, effectively, a bugle, if the player doesn't
make use of the valves. This is achieved by stretching the muscles around
the lips, compressing the mouthpiece tighter against the player's lips,
and
blowing harder. As a high school player limited to producing just a few
notes above "high C", I always admired leading classical trumpet players
like Maurice Andre and Winton Marsalis who could play extremely high
notes.
However, even they can be seen to be struggling when producing the highest
possible notes on a trumpet.

Don

Dr. Donald G. Polvani
Adjunct Faculty, Physics
Anne Arundel Community College
Arnold, MD 21012

_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l


_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l