Sound requires a medium. It travels as regions of compression (particles squeezed together) and rarefaction (particles spread apart). No medium, no sound. Select different media below and watch how the wave behaves.
No medium, no sound.
The source pulses, but nothing propagates.
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Animation paused. Compression zones (blue) show where particles are bunched; rarefaction zones (amber) show where they're spread apart. Drag the scrub slider to step through the wave.