What can you do with an empty wine glass? (aka 'Wine Glass Normal Modes')

[sl8]

Wineglass Normal Modes

Harvard Natural Sciences Lecture Demonstrations

Published on Jun 28, 2010

The first two normal modes of oscillation for a wineglass subjected to amplified sound. The fundamental mode (529.3 Hz) and the second mode (1368.0 Hz) are observed with the help of a strip of paper and a strobe light.

The fundamental mode has 4 antinodes. This is the dominant frequency of the glass and is the easier of the two to find. We usually break the glass in this mode.

The second mode has 6 antinodes. To find its frequency we used HairerSoft's Amadeus Pro to find the approximate range and then zeroed-in more closely using a microphone and oscilloscope. We used a much higher sound intensity level than for the fundamental to produce the amplitudes pictured here.

Ear and eye protection should be used when trying this at home.

During filming we did not intend to break the glass. No audio was recorded along with the footage of the glass under the strobe, so we had to steal the sound of it breaking from other footage--hence the sudden "OOMPH" noise at 2:16 in the soundtrack.

For more details on our setup and references for further reading, see http://sciencedemonstrations.fas.harv...

Special thanks to Nils and Rob for letting us use the lab space.

[Permanut]

1. Cool.

And adding varying amounts of water to the glass changes the frequencies.

[ret5hd]

2. 1) Fill it 2) Empty 3) Repeat

Then finally, sometime in the late afternoon, start playing with it like this guy does.

[fleur-de-lisa]

3. What is an 'empty' wine glass? Mine is always at least half full.

[jberryhill]

5. Have you been stealing from mine? Mine is half empty

[fleur-de-lisa]

6. When you snooze . . .

you lose booze. Around me anyway.

I am an unrepentent wine thief!

[Corvo Bianco]

4. Sing it into submission