### Re: Tempreature of liquid and sound frequency!

Date: Mon Mar 26 12:51:26 2001
Posted By: Todd Jamison, Staff, Image Science, Observera, Inc.
Area of science: Physics
ID: 984889943.Ph
Message:
```
Good question, Winnie.  Although, I must say, I'm not entirely sure of the
answer.  I can tell you that the easiest way to find out is to run a small
science experiment yourself!

Here's my guess:  The ringing you hear is due to the resonant frequency of
the glass - not the water.  I love to do this myself, entertaining my
children by making different notes with different shapes of glasses and
different amounts of water.  I believe that the water "dampens" the ability
of the glass to resonate below the level of the water.  So the pitch goes
higher as you add water, because the amount of glass above the water gets
smaller.  If it is truly just the dampening effect of the water that changes
the pitch, I would have to say my guess is that the pitch will not change
with the temperature of the water.

(As an aside, take a look at the water surface as you perform the "ringing
trick".  Do you see little round circles in the water?  These are "standing
waves" that are caused by the vibration of the glass pushing on the surface
of the water.  )

On the other hand, the pitch MAY vary with the temperature of the GLASS!  As
you probably know, glass will contract or expand with temperature, just like
many other types of materials.  IF the glass contracts or expands much, I
would guess that its pitch would have to change.  Glass is, however, very
stable compared to, for instance, most metals.  So it might be that the
glass does not change enough to vary the pitch over the range of
temperatures that you would want to encounter.

IF, however, the pitch does vary with glass temperature, then you might
postulate that hotter water would conduct some heat into the glass, thus
raising the glass' temperature and hence the pitch of the sound.  Does this
sound plausible?
Can you think of an experiment (or several) that would allow you to confirm
or reject these hypotheses?  I'd be curious to hear your answer and the
results of your experiments.  Let me know how things go at
tjamison@observera.com.

Good luck and good science,

Todd Jamison
Chief Scientist, Observera, Inc.

```

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