Variable Length Resonators

DCS Code: 3D32.15 Last Updated: March 27, 2026
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Purpose

Demonstrates acoustic resonance in open and closed air columns. Students hear how resonance depends on tube length and driving frequency, distinguish open vs. closed pipe harmonic series, and can measure the speed of sound from resonant lengths.

Two metallic cylindrical resonator tubes on tripod stands with speaker drivers mounted on top, connected by cables to an Agilent function generator
Figure 1: Variable-length resonators: closed pipe (P1635, left) and open pipe (P1636, center) with speaker drivers, connected to an Agilent signal generator. The tubes have adjustable pistons to vary the effective length.