Hooked on Science: Create sound with aluminum rod

Using an aluminum rod and rosin you can create an ear-piercing sound that will grab your attention along with every dog in the neighborhood.

Materials

* 2 feet 1/4 inch aluminum rod

* Rosin

Instructions

STEP 1: Firmly hold the center of the aluminum rod horizontally using the thumb and forefinger of one hand.

STEP 2: Pinch and release a small amount of crushed rosin with the thumb and forefinger of the other hand.

STEP 3: Gently stroke the aluminum rod from the center to the end of the rod using your rosin coated thumb and forefinger. Repeat and slightly increase the pressure of your stroking hand until you hear a high-pitched tone.

Explanation

Every material has a set of natural vibrations. When you hold the aluminum rod in the center and stroke it with rosin coated fingers, your fingers slip and stick as they slide along the rod. This causes the rod to start moving with one of its natural frequencies of vibration -- a half-wave tone.

Jason Lindsey is a science outreach educator with Hooked on Science. Check out his website www.hookedonscience.org for webcasts and experiments.