Category Archives: Oscillations & Waves

Speaker, Cardboard, and Megaphone

Demo: OW-E-SC
Pira Index: 3E 20.00

 Lab Equipment  Directions
  1.  tape player with tape
  2. megaphone
  3. cardboard with hole as shown
  4. external speaker (on handle)
  5. RadioShack mini amplifier
  1.  Plug the tape player into the input of the mini amplifier. Attach the handled speaker to the ‘ext. speaker’ jack on the mini amplifier.
  2. Turn on the mini amplifier and the tape player and listen to the music through the external speaker. Bring the speaker against the cardboard hole and hear the change in volume. Note that the volume increases.
  3. Repeat this by using the megaphone in place of the cardboard.


Xylophone Demo

Demo: OW-D-XD
Pira Index: 3D 40.10

 Lab Equipment  Directions
  1.  xylophone and wood hammer
  1.  Strike the bars with the wooden hammer going from longest to shortest bar.
  2. Notice that the frequency gets higher as the bars get shorter and that the bars have been cut to the proper length to produce a musical scale.


Wineglass Resonator

Demo: OW-D-WR
Pira Index: 3D 40.50

 Lab Equipment  Directions
  1.  wineglass
  2. cup of water
  1.  Wet index finger in water.
  2. Run finger around top edge of wineglass. If done properly, a high-frequency noise will be emitted by the wineglass.
  3. Now run your finger around the bottom of the wineglass while holding on to the stem. The same effect should occur.
  4. Now put water inside the wineglass and repeat step 2.
  5. Notice the waves generated on the surface of the water.


Singing Rods

Demo: OW-D-SR
Pira Index: 3D 40.20

 Lab Equipment  Directions
  1.  Rosin (looks like yellow rocks)
  2. two 3′ aluminum rods
  3. one 4′ aluminum rod (scored at nodal positions)
  1.  Hold a 3′ rod in each hand, at midpoint with thumb and finer. Tap each straight down on the floor and hear them sing. Beats can also be heard.
  2. Rub fingers with rosin with other hand hold 4′ rod at midpoint with thumb and finger.
  3. With rosined fingers, pull rod from middle to end continuously until it begins to sing.

Singing Pipes

Demo: OW-D-SP
Pira Index: 3D 30.70

 Lab Equipment  Directions
  1.  2 singing pipes
  2. propane torch
  3. heat glove
  1.  Put on the glove.
  2. Hold a pipe with the screen towards the bottom end.
  3. Direct the flame from the torch into the end of the pipe for about 5 sec.
  4. Hold the pipe vertically for it to “sing”.
  5. Turn horizontally and it will stop.



Demo: OW-D-SO
Pira Index: 3D 20.10

 Lab Equipment  Directions
  1.  sonometer
  2. bridge
  3. large C-clamp
  4. slotted weight set
  5. 2 large weight hangers
  6. 10 – 1kg weights
  1.  Set up the equipment as shown.
  2. Put the 1kg weights on each hanger.
  3. Move the bridge to vary the frequency of the wire.
  4. Add additional weights to increase the tension and frequency of the waves.


Standing Waves in a Flame

Demo: OW-D-SF
Pira Index: 3D 30.50

 Lab Equipment  Directions
  1.  standing waves apparatus and base
  2. AudioSource amplifier
  3. MoVo MP3 player
  4. igniter
  1.  Connect the waves apparatus to the gas outlet. Connect the BA leads to the audio amplifier.
  2. Connect the MP3 player (red lead) to the ‘unbalanced’ plug on the back of the amplifier.
  3. Turn on the gas and light the apparatus. Adjust the flame to 1″.
  4. Turn on the amplifier and the MP3 player and set volume on amp to silver arrow and MP3 to 90%.
  5. The first sound is the 570Hz fundamental tone, then 1140 and 1497Hz. These are followed by 2 very different melodies. You can toggle the MP3 player forward or backward at any time.