- No lesson on acoustics is complete without the didgeridoo. Impress your students with its very peculiar sounds.
- Can demonstrate the phenomenon of beats very easily.
- For additional physics see: http://newt.phys.unsw.edu.au/jw/didjeridu.html
- Mouth piece can be removed and washed.
- If you don’t already know how to play a didgeridoo, ask Adam for assistance.
- Located in L02, section C.
- Length of each tube determines tube’s resonance pitch. The longer the tube the lower the pitch. Tone produced by whacking a tube reveals its note of resonance. Resonance pitch can be changed by attaching the plastic end-cap.
- For additional demo ideas and see: boomwhackers
- Located in L02, section C2.
Copper pipes chime when hit (hang by loop and tap with hard object). Pipes are identical in size and composition, and are therefore identical in pitch.
To see how temperature affects pitch, dip one pipe in liquid nitrogen and cool for 1 minute. Tap both pipes to hear differences in pitch. Caution: DO NOT TOUCH COLD PIPE WITH BARE HANDS. USE CRYO GLOVES.
Pipes located in L02, section C-1. Ask for assistance with LN2.
- Nuts are tied to two separate ropes. Spacing between nuts on rope 1 is constant; spacing between nuts on rope 2 goes as the square of the distance from the end of the rope.
- Hang ropes vertically and drop onto wooden platform. When rope 1 falls sound made by nuts (hitting board) increases in frequency, indicating acceleration of rope. When rope 2 falls, the nut-hitting-board sound is periodic, due to r^2 spacing.
- Note: When hanging string, first nut (on bottom of string) rests upon board. So first nut does not fall- merely used as an a position anchor.
- Located in L02, section B3.
Demonstrate principles of sound amplification
Music Box is normally very quiet, and barely audible in a large lecture hall. But when the music box is pressed firmly against a solid, rigid object- like a table top or a blackboard-it becomes very audible. Press against the body of an acustic guitar for even larger amplification.
see demo at- http://www.arborsci.com/music-box-mechanism
- Determine the highest frequency of audible sound. Adjustable
whistle produces mostly frequencies inaudible to us. Lowering the pitch brings
the sound into most people’s audible range.
- Located in L02,
- Purpose: Demonstrate resonance and measure speed of sound.
- Two different resonance tubes are shown above.
For Smaller Tube
- Strike tuning fork on rubber pad; place fork near larger
opening of tube; slide inner tube in and out until resonance is heard. Use
tube length and frequency to determine speed of sound.
For larger Tube
- Use speaker and function generator to find resonant frequency
of tube. Once resonance is found, use vernier microphone to locate nodes and
anti-nodes.Use tube length and frequency to determine speed of sound.
- Located in L02,
- Measure speed of sound by placing tuning fork near open end
of tube and adjusting water level to find resonance.
- Located in L02,
- Listen to beat frequencies through speakers, while simultaneously seeing waves with oscilloscope. Use scope’s math function to add waves together. Resultant wave (shown in red, above) displays beats.
- Demo consists of 2 function generators, 2 speakers, and one
- Located in L02, section C2; Oscilloscope located in L35,
- Use on aluminum track, or on smooth, hard surface.
- Located in L02, section C2; in bin with doppler rocket.
Two people required to use this demo. Each person holds set of handles, and unwinds rope (about 20 m) . When one set of handles is quickly separated (handles initially held together, then quickly pulled apart) the football shaped “rocket” is forced to slide down the ropes. The rocket contains a noise maker (turned on manually) that exhibits Doppler shift when in motion. Users take turns launching and catching the rocket. Doppler affect can be heard by audience members in close proximity.
- Located in L02, section C2
- This demonstration has been used to explain how sound can
be used to break a wine glass, or to help illustrate principles behind the
Bohr model of the hydrogen atom.
- There are two configurations of loops from which to choose:
parallel to the floor or perpendicular to the floor.
- When changing accessories to the oscillator be careful to
lock the piston (as the oscillator is quite delicate).
- Mechanical oscillator, wire loop, and
function generator located in L02, section C2, in “Chladni plates”