Special Magic Canyon Creek and Magic Waterfall programs were created for these features. It only makes sense that the layout should sound like what you see. If the prototype made a noise, then it is likely audible on the GCD, as well. A voice may be processed with EQ, given an exaggerated dynamic range, or run through single ended noise reduction. But we must compensate for the fact that they will perform for the public at appropriate scale volume levels.
Real sound happens in a full scale ambiance, that's why it sounds real.
In order for our scale voices to sound real, we must scale the ambiance back up to the full scale listener's world. It may seem backwards at first, but as we turn the voice itself down to a scale volume, the quieter background ambiance disappears below the threshold of hearing, sometimes vanishing completely. This is the primary reason why real recordings of real environments do not always work as well at scale volumes, the ambiance of the environment around the sound becomes inaudible at very low volumes. We must design an ambiance that reconnects the original voice to the full scale listener, just think of it as a magic concert hall in which we can create any listening environment. It is also a secret.