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[Phys-L] Re: sound frequency in helium



I was going to suggest, in a bell jar, ringing a bell or tuning fork w/
and w/o He to see how much, if detectable, the different loading changed
the freq., but vickie can do it w/ her resonance tube using a continuous
sine.

Frohne, Vickie wrote:

Hmmm....good question. The increase in the frequency of sound due t=
o helium is not limited to human voices. For example, the pitch of a =
vacuum pump's "chugging" sound rises noticably when helium is introdu=
ced to the system (as when one finds a large leak). We also use heli=
um in the Pasco resonance tube apparatus (a tube with speaker at one =
end) to measure the change in the speed of sound that occurs when a b=
alloonful of helium is squirted into the apparatus. We used clicks (s=
quare wave pulses) from the speaker, so I don't recall whether or how=
much the pitch of the sound increases. I think it did, but I'd have=
to try again to make sure. It's been a while since I did this exper=
iment. - Vickie


-----Original Message-----
=46rom: Forum for Physics Educators on behalf of Julie Quah
Sent: Sun 4/17/2005 9:40 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: sound frequency in helium
=20
hi thanks for the enlightening explanation. Does it follow that if a =
=3D
pure=3D20
sound wave (i.e. one produced by tuning fork) is used in such activit=
=3D
y, the=3D20
pitch will not appear to change, since there is only one frequency?

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