Science Buddies: "Ask an Expert"

Hi,
I'm doing an experiment on the effect of water volume on the frequency of the sound that is produced. This relates to the singing wine glass phenomenon. I have done my experiment and found that there is a negative correlation between the two: the higher the volume, the lower the frequency of the sound.

Why? I have no idea why there is a negative correlation. Could anyone help me out?

Thank you already in advance!

Hi Jaakkojaakko,

The "singing wine glass" is a fun system that's well-studied. A quick online search yields many results-- some of these will appeal to you as a scientist.

In a brief answer to your question, the liquid molecules near the wall of the glass absorb some of the vibrating energy. If they're absorbing and dissipating this vibrational energy, the vibrational energy of the glass decreases. Lower energy, lower frequency. More liquid absorbs more energy, lower frequency sound.

The wall of the glass (when filled with pure ethanol) looks like this:

https://figshare.com/articles/silica-et ... if/5435224

where the yellow/red sticks on the bottom are silica crystal.

Other experiments investigate changing the density of the liquid and looking at the "modes" of the vibrations as one varies the volume.

-John