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Re: [Phys-l] frequency and wavelength of sound in air



I suspect the difference in the drag (Q change) will change the driver frequencies. Also,like in a wind instrument, since the speed changes the resonant frequencies, so will the driving frequency change. I agree most of the He effect is a change in the timbre, but I suspect, like lips on the mouth piece of a brass instrument, the vocal folds are affected by resonance.

http://books.google.com/books? id=iiCZwwFG0x0C&pg=PA200&lpg=PA200&dq=wind+instrument+temperature+% 22pitch+OR+tuning% 22&source=bl&ots=j2nMoN7jQZ&sig=Okz2cuV2Geed7wvMMWhKm- m_AGI&hl=en&ei=omrYSYbAHoPQswOPtJ22Cg&sa=X&oi=book_result&ct=result&resn um=3#PPA201,M1


bc later read the reference and found that it mentioned the slight effect of a changed Q.

p.s. I didn't look at the graphs carefully, but .. the resonance selects the amplitudes of the harmonics. The harmonics are the modes of the vibrating vocal folds. This is what changes the timbre, not the change in their frequencies, except for my claimed effect above. This is like the effect of cylindrical vs. conical instruments and the flare of the bell in brass instruments, and some wood winds too -- sound board, mute, etc. in strings.

On 2009, Apr 05, , at 01:34, Savinainen Antti wrote:

Hi,

Curtis Osterhoudt pointed out a good source explaining what helium does to speech:

<http://phys.unsw.edu.au/phys_about/PHYSICS!/SPEECH_HELIUM/ speech.html>

Let me quote the source:

"The speed of sound is greater, so the resonances occur at higher frequencies: the second resonance has been shifted right off scale in this diagram."

This is fine and makes perfect sense. But then the text continues:

"The flesh in your vocal folds still vibrates at the same* frequency, so the harmonics occur at the same frequency."

The flesh part makes sense but why the *resonances* occur at higher frequencies whereas the *harmonics* occur at the same frequency?? I thought that in this context resonances and harmonics mean the same thing. What am I missing?

Regards,

Antti








Antti Savinainen, Ph.D., B.Ed.
Adjunct Professor (University of Jyväskylä)
Senior Lecturer in Physics and Mathematics
Kuopion Lyseo High School
Finland
E-mail: <antti.savinainen@kuopio.fi>
Website: <http://kotisivu.dnainternet.net/savant/>


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