Study Guides | 2. sound | Glass Harp

Study Guide: Glass Harp

  1. Friction between our fingers and the glass causes the glass to vibrate.
  2. The vibrating glass causes the air to vibrate, which our ears interpret as sound.
  3. Different glasses vibrate at different frequencies, which our ears interpret as tones.
  4. When water is added to the glass, it can alter the frequency of the vibration, which changes the tone.
  5. As the water vibrates, we can see the compression waves on the surface of the water.
  6. Glass, which is a very rigid substance, can shatter if the compression waves become too strong.
  7. We interpret random sound as noise. We experience certain sounds as beautiful and harmonious, and we create music with them.
  8. Some people seem to have a gift for sensing sound. They may have perfect pitch, and have the ability to imagine and spontaneously create complex musical arrangements. Mozart and Beethoven are well-known examples of a musical geniuses.

Materials

  1. One or more wine glasses, drinking glasses, etc.
  2. A little bit of vinegar
  3. Tap water
  4. Dishwashing detergent

Directions

  1. Wash off the natural oils on your fingers with dishwashing detergent.
  2. Moisten your fingers with a little vinegar, and rub them on the rim of a wine glass until it rings.
  3. Fill a wine glass about $ \frac{3}{4} $ full of water, and make it ring again.
  4. Observe the vibrations at the surface of the water as the glass vibrates.

Variations

  1. Try different sized glasses, with different amounts of water in them.
  2. Try tuning several glasses and playing a song.

Boy Breaks Wine Glass with Voice (1:34)

Don’t try this at home!

Sugar Plum Fairy by Tchaikovsky - Glass Harp (2:06)

Street Artist Playing Hallilujah (3:47)

Für Elise on Glass Harp (3:41)

Questions

  1. What do you think causes the glasses to ring?
  2. What do you think causes some glasses to ring better than others?
  3. What effect does filling the glasses with water have on the ring?
  4. What did you observe in the patterns the ripples make on the water?
Source: https://class.ronliskey.com/study/physics-7/sound-ripples-in-the-water/