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Helium and Pitch
Name: Andrew
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
I designed an experiment with a "chamber" that I infused
with helium gas and then tested various noise producing devices:
tuning fork, radio, recorded voice. When exposed to helium none of
these sounds changed -- unlike my voice, which changes when I take a
small breath of helium gas. I read your response regarding why the
human voice changes, but why does not helium change the vibration of
these other (non-human) noise makers?
Replies:
The sources that you used all have a the frequency set by something
other than the speed of sound in air (or helium). The tuning fork
vibrates according to its own mass and stiffness, the radio and recorded
voice speaker is driven by its electronics. The physics of the human
voice is a bit more like a trumpet, in which the speed and wavelength
of the standing waves set up in the vocal tract define the frequency of
the sound.
Richard Barrans
Department of Physics and Astronomy
University of Wyoming
Why does it appear our voice changes when inhaled helium is exhaled during
vocalization? The high concentration of helium actually moves the now gas
mixture faster,....this causing the vocalization to change. In a true
confined space with helium blowing, we could, with correct instrumentation
measure changes in sound / speed.
I would try to measure all gases in this chamber, have the helium gas
forced over various sounding devices i.e. speaker, tuning fork, listen and
perhaps consider using a triggered sweep oscilloscope.
Prf. Przekop, Physicist
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Update: June 2012
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