Adopt one today. There are many boulders out there looking for a good home. Nothing is better than the sound of water in the garden. Especially on a nice summer night. This particular stone is a basalt column which is a very dense volcanic rock.
A recirculating bubbling boulder really does make a great companion to any landscape. They are great as welcoming accents or clustered together for a very full sound. If you are using just one make sure to place it close to where you do most of your outdoor living. If it is placed too far away it might get lost in the rest of the garden. All that is needed is a nearby power outlet and enough room to dig a basin to hold the water.
Bubbling boulders fit into almost any space. If you have a open space, a larger and more prominent stone is preferable. If your space is more intimate, a smaller boulder with nice subtleties is probably best. Your local stone supplier should have a selection of pre-drilled stones to choose from, or you can pick your own and have them drill it for you. The character of the stone will determine the amount of noise it will produce. A smooth stone like the one above has a very consistent bubbling sound, while a rough stone will have a inconsistent splashing sound. If you already have a space in mind these characteristics will help you pick your new garden companion.
Here is a picture of basalt before it is harvested.
Columnar basalt at Sheepeater Cliff in Yellowstone. pic. from wikipedia