There are some types of sounds, created by on what water falls.
The sound may be produced when water falling directly to a water surface or falling on a rocks and then sliding down on stones.
  The waterfall height s most important factor. Lower to 5” to 6” may little decrease sounds but as increased to 20″ – to 30”, sound increases are considerable. From all factors while building backyard waterfalls, height is the most clear to understand.
  You can experiment with garden hose, bucket and sewer utilities, and find out the best waterfall height.