Activity 13.3: Use two tubes and a clock to test sound reflection.

Solution & explanation

Direct one tube toward a reflecting wall with a ticking clock at its outer end; listen through the second tube. Adjust the second tube until the tick is strongest. Measure angles from the wall’s normal: strongest reflection occurs near i = r and in the same plane. Lifting the receiving tube out of that plane reduces the received tick. Avoid a direct sound path as far as practical.