Abstract

Objective

The goal of this project is to investigate how the musical note produced by a wine glass is affected by the fluid level in the glass.

Introduction

Benjamin Franklin is a celebrated figure from early U.S. history. He is famous as a statesman, scientist, democrat, aphorist, printer, and inventor. Although many will be familiar with the Franklin stove, few have heard of the armonica, a musical instrument whose sound source was a series of resonating glass vessels (Wikipedia contributors, 2007).

The principle of Franklin's armonica can be demonstrated with a wine glass. Use one hand to hold the glass steady at the base, then wet a finger of the other hand. Press gently on the rim of the glass with moistened finger, then draw it in a circle around the rim of the glass. When the pressure and amount of moisture are just right, the slight friction between your finger and the rim of the glass will cause vibrations in the sides of the glass. There is a particular frequency, called the resonant frequency, at which the sides glass will vibrate most easily. The resonant frequency of wine glasses is typically within the range of human hearing (20–20,000 Hz), so you hear the resulting resonant vibration as a tone.

In this project you'll investigate the answer to a simple question: How does the tone change as the fluid level in the glass is changed?

Terms, Concepts, and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• Vibration
• Musical note names and frequencies
• Resonance, resonant frequency
• Armonica or glass harmonica

Questions

• How does a wine glass produce sound when you rub on its rim with a wet finger?
• How does the frequency of the note produced change as fluid is added to the glass?

Bibliography

• These pages have background information on the physics of "singing" wine glasses:
  
  • HowStuffWorks, 2007. "How Can You Make a Wine Glass Sing?" Howstuffworks.com [accessed September 11, 2007] http://recipes.howstuffworks.com/question603.htm.
  • Ansell, D., 2006. "Making Music with Wine Glasses," Naked Scientists Kitchen Science 2006 [accessed September 11, 2007] http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/making-music-with-wine-glasses/.
• Here are some references on Benjamin Franklin's armonica:
  
  • Wikipedia contributors, 2007. "Glass Harmonica," Wikipedia, The Free Encyclopedia [accessed September 14, 2007] http://en.wikipedia.org/w/index.php?title=Glass_harmonica&oldid=157541700.
  • Scientific American Frontiers, 1998. "The Art of Science: Ben Franklin's Harmonica," PBS [accessed September 11, 2007] http://www.pbs.org/safarchive/4_class/45_pguides/pguide_804/4484_franklin.html.
• This project is based on the following entry to the 2007 California State Science Fair:
  Lent, M.S., 2007. "Whistling Wineglasses: Is Vibration Frequency Linearly Related to Water Volume?" California State Science Fair Abstract [accessed September 11, 2007] http://www.usc.edu/CSSF/History/2007/Projects/J1624.pdf.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• One (or more) wine glass(es)
• Water
• Electronic chromatic tuner (e.g., Korg CA-30, widely available in music stores and online)
• Graduated liquid measuring cup
• Optional: piano or keyboard for comparing notes
• Optional: kitchen scale to measure the mass of the glass(es), such as the Fast Weigh MS-500-BLK Digital Pocket Scale, 500 by 0.1 G, available from Amazon.com

Experimental Procedure

1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
2. Determine how much water the wine glass can hold.
   1. Fill the glass with water, then pour the water into a liquid measuring cup.
   2. Repeat at least three times, and calculate the average of your measurements.
3. Turn on the chromatic tuner and place it near the wine glass.
4. With the wine glass empty, sound a note by rubbing on the rim of the glass to determine the fundamental frequency of the glass.
   1. Hold down the base of the glass with your non-dominant hand.
   2. Wet your index finger of your dominant hand with water.
   3. Rub your finger around the rim of the glass while pressing down gently.
   4. With just the right amount of pressure, the glass will vibrate, sounding a musical note.
   5. Use the reading from the chromatic tuner to determine the note.
   6. Optional: you can also compare the note frequency with notes sounded on a piano or keyboard to determine the fundamental frequency of the wine glass.
5. Now add a measured amount of water to the glass and repeat the procedure from the previous step to determine what note the glass now sounds. Express the volume as a percentage of the total capacity of the glass:
   
   [percentage volume] = [volume of water in glass]/[volume of water to fill glass] ×100
   
6. Repeat for several different volumes of water.
7. You can organize your data in a table, like the one below:

   Volume (%)	Musical note	Frequency (Hz)	Comments/Observations

8. Make a graph of your results, with the measured note frequency (in Hz) on the y-axis and the percentage volume on the x-axis. How does the note frequency change as the glass is filled?

Variations

• Try the experiment with wine glasses of different size and/or shape. Can you draw any conclusions about the relationship between the size/shape of the glass and its fundamental frequency of the glass? For this experiment it will be helpful to have a kitchen scale in order to measure the mass of each glass.
• You can also make musical notes by blowing over the top of a narrow-necked bottle. What happens in this case as you add fluid to the bottle? Is the mechanism for producing the sound the same or different than when you rub the rim of a wine glass? For more details, see the Science Buddies project Blowing Bottletops: Making Music with Glass Bottles.

• For more science project ideas in this area of science, see Music Project Ideas.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

This project is based on the following entry to the 2007 California State Science Fair:

• Lent, M.S., 2007. "Whistling Wineglasses: Is Vibration Frequency Linearly Related to Water Volume?" California State Science Fair Abstract [accessed September 11, 2007] http://www.usc.edu/CSSF/History/2007/Projects/J1624.pdf.

Last edit date: 2011-11-18 12:00:00