A dramatic (and loud) demo of resonance, harmonics, nodes and anti-nodes.
These rods emit a VERY LOUD pure tone when stroked. The nodes are marked on the rods to indicate where you should hold them. Standing longitudinal waves are set up in the rod by stroking the rod with your fingers (coated with the included rosin). Investigate the effects of different lengths and holding the rod at different nodes.
How it Works
Sliding your fingers on the rod (with the help of rosin) causes the metal rods to vibrate. When caused to vibrate at their natural frequency the rods create standing longitudinal waves. At this point of resonance the rods have points that don’t vibrate at all (nodes) and points that vibrate at their maximum (antinodes). The rods will always have antinodes at either end but they can vibrate a a few patterns with equally spaced nodes in between. You can force the rods to vibrate in a specific pattern by holding it at the place you don’t want to vibrate, causing a node at that point. The different patterns correspond to different wavelengths and therefore different frequencies or pitches.
- Two Aluminum Rods. Approximate length of 20″ (500 mm) and 30″ (750 mm)
- Bag of crushed rosin to lightly coat your fingertips