Steel spring pendulum, inverted, vibrates at 10 Hz.

3C20.16 • B+45+0

diagram for demo

InfraSound: not audible: A flat clock spring 40 cm. long is clamped to the lecture table. 100 gm. slotted weights can be clipped to the spring to vary the loading (and the period). The spring steel pendulum vibrates under 10 Hz,-thus is not audible, but compresses the air and produces pressure waves. Same apparatus as B+10+30

Related Demos

3C20.40 Savart's wheel: Toothed wheel and cardboard or air jet. 3C20.30 Siren: large, electric motor driven. 3C20.30 Compressed air jet blows through spinning disk with holes. 3C20.40 Sprockets on shaft rotate against a card to make sound. 3C20.15 Galton's whistle: Compressed air whistle. 3C20.16 Limit of audibility: Set of rods that ring at different frequencies.
B+45+5 Giant tuning fork, barely audible, displayed with stroboscope. B+45+10 Ultrasound transducers (40 kHz) as both sources and receivers. B+45+15 Bell ringing in a jar evacuated with pump. B+45+20 Savart's wheel: Toothed wheel and cardboard or air jet. B+45+25 Siren: large, electric motor driven. B+45+30 Compressed air jet blows through spinning disk with holes. B+45+32 Twirling Tube B+45+35 Sprockets on shaft rotate against a card to make sound. B+45+40 Caruga horn: Varigated tube to blow through B+45+42 Hoot Tube B+45+45 Galton's whistle: Compressed air whistle. B+45+50 Helmholtz resonators drive radiometer vanes, using tuning forks. B+45+55 Casio electronic synthesizer with amp and speaker. B+45+41 Feedback from microphone/speaker system. B+45+51 Helmholtz Resonators with tuning forks and a candle B+45+60 Applet: Vibrational Behavior of an Empty Beer Bottle B+45+65 Applet: Vibrational Modes of a Tuning Fork