# measuring frequency of a resonating wineglass

Hi,

I’m doing a physics project where I have to find the specific frequency of a resonating wineglass.
I’ve tried Analyze > Plot Spectrum, but I’m a little confused as to what it is telling me.
If anyone out there knows anything about physics it would be a great help! Thanks!

Do tell more…
How are you making the glass resonate?
How are you recording the sound/vibration?

Do you know how to take a screenshot on your computer? If so, paste a screenshot of the spectrum analysis.

I am rubbing the rim of the glass with my finger to make it vibrate and then recording as soon as i take my finger off.
The recording is being made with a regular microphone.
I can’t paste the screenshot but I think the graph may read that the crest is 485Hz and the trough is around 9000Hz…
I’ve tried it several times and I am getting approximately the same measurements.

This is what we know about Plot Spectrum:

For your experiment you may want to set the “Size” dropdown to 16384 which will give finer frequency gradations. Also turn on Grids and set the axis to “log frequency” - then it will look like a frequency response plot like you used to see in reviews of high-end audio equipment.

– Bill

And BTW you are unlikely to find a single frequency - you should see a dominant fundamental tone - but also expect to see some overtones too.

WC

Pinging the wineglass is sufficient to find the resonant frequency,
if you rub it it is a driven oscillator which could have a different resonant frequency to it’s natural resonant frequency.

BTW Here is a nice shattering-wineglass-with-sound-at-resonant-frequency video … http://www.acoustics.salford.ac.uk/feschools/waves/wine1video.htm

To collect all that.

– Start the recording (in a quiet room)
– Smack the glass with your finger or a pencil to get it ringing.
– Stop the recording after the ring dies substantially.

The resonant frequency is found by analyzing the wave after the impact but before the ring dies out. That will be the natural resonant frequency of the glass in, we assume, free air.

The lowest frequency, highest peak in the spectrum display will be the frequency, assuming you don’t have a crappy sound card. If you analyze the wave too soon – during the smack-- you will get the same Driven Oscillator problem as noted above. That’s a false reading. If you record in a noisy kitchen, you could well be measuring the resonant frequency of the garbage disposal or dish washer.

Koz

BTW2
where you hit the glass (rim, bowl,stem) couldl affect the note produced: it will have different modes of vibration each with its own resonant frequency.
The primary mode will be due to the bowl ovalling.

<<>>

I’d like to buy a set of fine, tall, crystal stemware with good bowl ovalling, please.

Koz