Doppler Effect I-Beams - Physics Demonstrations - Doppler Effect I-Beams | Physics Undergraduate Labs

Purpose

Two identical I-beam tuning forks produce slow (or no) beats when stationary. Swinging one beam toward and away from the class changes the beat frequency via the Doppler shift, giving students a direct auditory experience of how source motion alters perceived frequency.

Two aluminum I-beam tuning forks: a smaller beam with a string loop (left) and a larger beam suspended from a ring clamp on a bench clamp stand (right), in front of a chalkboard

Figure 1: Two I-beam tuning forks with the bench clamp stand assembly. The larger beam hangs from the ring clamp; the smaller beam is held by hand and swung toward and away from the audience.