Resonance frequency of a wine glass experiment

[Zoro]

Homework Statement

My group and i need to do an experiment for school. We decided to investigate the effect of water level in a vine glass (or volume) on the resonance frequency. Basically does the resonance frequency change when you change add water to the glass. I would just like some help modelling my experiment. We plan on finding the resonance frequency by circling two wet fingers around the rim. We would record this sound and calculate the frequency using a program on a laptop. We repeat with water in the glass. Am i in the right track and what can i do to improve my experiment.

Homework Equations

The Attempt at a Solution

Basically we haven't done the experiment yet but you can see my attempt/ plan for the experiment under 1.

 

[mfb]

That should work.

Other things to consider: does the speed of the fingers matter? How do you describe the shape of the glass, and how do you quantify its water level?

 

[Zoro]

Would i still be able to find the resonance frequency by tapping the glass and recording the sound on my phone or laptop. We do not want to invest in a microphone so is a phone or laptop fine. Which one would be better. We have a HTC M8 and Galaxy S4 btw.

 

[mfb]

No idea, but you can test both.

 

[BvU]

And for analysis you might look at the PC oscilloscope here or the evaluation version of this one

 

[Zoro]

oh wow thanks you! I needed to find a program for the data analysis

 

[gneill]

A possible extension of your experiment might be to see what effect (if any) using a fluid other than water might have on the level vs frequency relationship.

 

[Zoro]

How do you think i can extend my experiment. I like the idea of trying out another fluid.

 

[NascentOxygen]

How do you think i can extend my experiment. I like the idea of trying out another fluid.

Maybe you could replace the air column with a different gas. CO₂ is heavier so should stay in place if there's no breeze. To have a lighter gas stay in place it may be feasible to cap the vessel with a soap bubble film, but I'm not confident.

 

[mfb]

You generate a breeze by moving your finger and hand along the rim of the wine glass. The soap bubble thing might work, but I wouldn't expect too much from it.

 

[NascentOxygen]

The purpose of rubbing a wet finger around the rim is to introduce random impulses into the glass.

On 'The Brain' last weekend (a Chinese TV talent show) they had a contestant who, by identifying the musical tone produced and relating that to the level of water, could determine the volumetric content in a wine glass. He was presented with the tone from glasses filled to different levels, and succeeded in estimating their combined contents to an accuracy of better than 3 mls.