Question:
Can sound be described as a wave?
Materials:
- Stereo speaker set
- Computer/smartphone
- Measuring Tape
- Ruben's Tube Construction
Instructions:
Instructions (Spatial Sound Wave Interference):
- Set up speakers ~ 1 ft apart, facing outwards in the same direction
- Connect to computer/smartphone
- Use frequency generator app to play low frequency (200-400 Hz) sound
- Walk around the room, listening for loud and quiet spots, representing maxima and minima in wave interference
- Optional, use additional smartphone app (Da Tuner lite works well) to measure sound intensity in decibels to quantify maxima and minima
- When you find a quiet spot (minima), turn off or cover one of the speakers. The sound should increase since there is no longer any interference.
- Measure distance from speaker pair to maxima and minima to map the interference distribution
Instructions (Beat frequency Sound Wave Interference)
- Use same speakers, or internal stereo speakers of smartphone or computer
- Use two apps or videos to play nearly identical sound frequencies (eg. 500 and 501 Hz)
- Demonstrate they sound almost the same when played separately
- Play the two together to show the appearance of a difference (beat) frequency, equal to F2-F1
- Have the students time the beat frequency. Try different frequencies with the same and different frequencies.
Instructions (Rubens Tube)
- Set up tube in area with minimal drafts/airflow. Even normal building AC can disrupt the flames
- Use small flow of propane and lighter to ignite flames spaced on the tube
- Use speaker to play lower frequency (~200 Hz) sound
- Adjust propane flow for stable, fairly low (several inches) flame height
- Adjust volume, frequency and speaker proximity to observe standing wave appearance of flames
- Finally, use speaker to play songs into tube, observing flame behavior to higher and lower frequency tones in the song.