3B22.10 • Standing Waves : Melde’s String Vibrator

Location: Floor Demo

Photo shows demonstration used at the University of Texas at Austin

---

Instructions / Notes:

• A thin bungy cord is driven under tension to show a variety of standing waves.
• A digital frequency generator with a built-in amplifier drives a speaker coil, which vibrates the string.
• The control knob ranges from 15hz to 80 hz to produce 1,2,3 and 4 nodal points.
• An optional strobe light can be used to freeze perceived motion of the string.

---

Demo Staff:

• Test this demo BEFORE class to make sure the frequency modes are still accurate.
• If nodes are not activating at the written frequency, write down the new frequency for each node and place it over the latest note.
• Be sure that you include the date on the note!

---

Last updated on June 22, 2026