It seems likely this drawing was inspired by the real Victoria Falls, Zimbabwe and Zambia.
Photographer: De Agostini Editorial/Getty Images
The Victoria Falls are a result of the Upper Zambezi eroding a gorge from sandstone that had filled cracks in the underlying basalt.
Niagara Falls is only loud up close: it might be 90 db from a few meters away but it's not that loud at any distance. Certainly not enough to bother local residents. (I was there a few years back).
Even when you go 'behind the falls' its not THAT loud.
Also, it's much noisier at the bottom than the top.
You can hear it from a very long way -- low ...
Yes, but it is not easy.
It won't work on earth but it could work on a earth like planet.
everything in the image is possible getting it all in the same place is the hard part.
we have rocks structures like that on earth, they are the product of wind erosion or wave erosion.
But you need lighter gravity to get them on that scale.
So what you could have ...
One possibility, especially if the people are a species that evolved in a running-water environment (rapids and lesser falls, specifically), is for the people to have evolved a very narrow-band voice at a high frequency, and hearing that filters other sounds but selectively amplifies the frequency band used for speech.
Waterfall noise is extremely broadband,...
What you need a very large river that flows very slowly, as would be the case on a flood plain. This will enable the river to form meanders and oxbow lakes. Then the same arrangement coming from another valley. At the confluence where the two rivers meet to form an even bigger river, there is a large underground limestone layer which has been eroded by water ...
I would expect some minimum level of ear protection would be called for. In Greek myths, Ulysses put wax in the ears of his men to protect them from the siren's call (he, himself, had to hear it, so he had them tie him to the mast and ignore his orders until they were at a safe distance).
The bigger issue would be that the 90dB noise would drown out ...
This is just to add to the other answer for completeness: You don't have an especially high flow rate, and there's a fair chance your water will largely "stick" to the edge of the region and pour down in a rather unimpressive fashion - no pretty waterfalls without some drainage works.
How fast? About 2.8L comes over each 10cm section ...
Yes, but what would need to happen is quite hard in nature. The rivers probably originated close to each other, because then all the gushing water would slowly erode into separate paths which is quite common. However, the rivers meeting again is quite rare as the meanders that each river has formed will go different ways.
However, in the background there ...