Set up a small waterfall in your garden. An easy way to do this is to support a stone or concrete basin on a pile of rocks and place a larger basin at the base of the rocks. Leave at least 18 inches between the basins to make room for the bamboo feature. Put a small pump in the lower basin and feed the outflow tubing into the upper one.
Drive two bamboo pegs into the ground underneath the upper basin. The pegs should be about 2 inches in diameter. Drill a 1/2-inch hole through both pegs at the same height so a wooden dowel can pass through both of them.
Cut one end of a 12- to 24-inch length of bamboo that is 2 to 4 inches in diameter at a 45-degree angle with a handsaw. Drill a hole through the bamboo about a third of the way from the angled end, using a 3/8-inch drill bit.
Hang the bamboo between the pegs with a length of 3/8-inch wood dowel. You'll have to force the dowel through the pivot piece, but it should fit loosely in the pegs. The bamboo should pivot freely.
Support the heavy end of the bamboo pivot on a large rock or a piece of bamboo supported on rocks, so that it makes a sound when it falls. Put a weight in the heavy end if you want to amplify the sound. Alternatively, put a rock or piece of bamboo under the spout so the spout hits it and makes a sound when it fills with water and falls.
Route the water from the upper basin so that it falls into the angled mouth of the bamboo pivot. You may be able to do this with rocks, by carving out the rim of the basin or by fashioning a spout from bamboo.
Adjust the water outflow so that it takes the pivoting bamboo anywhere from one to 10 seconds to fill, depending on your preference. If you can't adjust the outflow of the pump, create another spillway for the water so that only some of it falls into the bamboo feature.