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Suppose, for instance, you lived in a world filled with nasty monsters and other creatures of the night, all of whom wanted to kill you and eat you in various ways. Now, the good news here is that we all know such creatures cannot cross running water. So, if you're in danger, all you need to do is hop over a running stream and you're fine.

Now, if we take this to it's logical extreme, the best thing to do is to build a city on a river so that it'll always be surrounded by running water. Or, (because this is going to be in a fantasy novel and what's the point of fantasy novels if they aren't fantastic) build your city between twin gigantic waterfalls.

To clarify, this is how the waterfalls works. They are both fed by a single gigantic river, the river itself it incredibly wide and deep and has hundreds of tributaries making it up. At a point, the river splits into two equally sized smaller rivers, both of which split off and then curve around after about a few mile until they're parallel to the original river's course. At that point they continue on for a good ten miles until they reach the twin waterfalls. Thus you have a nice square patch of land to build a decent-sized city, at least by Dark Age standards, cheerfully protected from all the nasty things that go bump in the night thanks to your waterfalls.

There's only a single problem here, and that is sound. You see, waterfalls can get very loud by nature - Niagara Falls, for instance, has a sound level of around 90 dB, equivalent to that of a lion's roar. Now, no matter how loud the falls the people living in the city don't care - a little noise beats dying. But they're definitely going to want to make a few adjustments to day-to-day life to make living around the waterfall easier.

Assume a Dark Ages level of technology, and assume a noise level similar to that of Niagara Falls. What kind of adjustments would you expect the inhabitants of this city to make to cope with the constant noise of the waterfall?

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    $\begingroup$ Why not ask people who actually live in the cities of Niagara Falls (there are two, one in the US, one in Canada) how they deal with noise from the falls? And how loud is typical modern urban noise from traffic &c? $\endgroup$ – jamesqf Apr 1 at 16:47
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    $\begingroup$ The real problem is waterfalls move, they don't stay in the same place, erosion moves them fairly quickly. Niagara, which is on fairly hard rock, moves around 3ft a year. That adds up quickly. $\endgroup$ – John Apr 1 at 17:39
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    $\begingroup$ Sound pressure drops with 6 dB for each doubling of the distance from the source. If the waterfall makes a sound of 90 dB at 1 meter distance, at 16 km the sound will drop to 0 dB. $\endgroup$ – AlexP Apr 1 at 18:08
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    $\begingroup$ "At a point, the river splits into two equally sized smaller rivers" Rivers don't work that way! $\endgroup$ – nick012000 Apr 2 at 3:21
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    $\begingroup$ @nick012000: Oh yes they do. What the question says is that the city is built on an island in the river. $\endgroup$ – AlexP Apr 2 at 7:21
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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 frequencies carry well -- but it's not loud until you get very close. At the viewing areas you can talk normally.

A lot depends on the exact layout and how big the 'island' with the city is and how far from the falls. Properties closest the falls might be cheaper than those further away. Certainly, as has been suggested, those most affected will, like metalworkers etc, develop sign language and lipreading skills. Rich folk will have wax earplugs and insulated quiet rooms in their cellars where they can enjoy the luxury of peace and quiet conversation.

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    $\begingroup$ Additionally, the taller the falls are, the quieter it will be at the top, the sound is mostly made at the bottom where the water hits. If the falls are fantastically tall, it'll be mostly silent at the top. $\endgroup$ – Mathaddict Apr 1 at 20:35
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    $\begingroup$ Another note, speaking from experience: You don't actually hear the noise from waterfalls unless you concentrate on it once you have lived there for a bit. $\endgroup$ – Nacorid Apr 2 at 11:49
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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, but it's "pink" -- that is, intensity drops off as frequency increases. The deep roar can vibrate your chest, but the high hiss is far softer.

Narrow band voice is fairly easy -- use a whistle tone and resonate it in the sinuses rather than the lungs. Instead of a larynx, they'd have a sort of biological chiff and fipple. Hadrosaurs used this kind of sonic apparatus, and (based on simulations and reconstructions) could make themselves heard in a "normal" environment for literally miles.

For hearing, all that's needed is to have a tuned resonating chamber in the ear -- this will selectively amplify frequencies close to the its resonance. For compactness, this chamber could be half or a third the size of the vocal resonators, and the voice use a second or third harmonic, like overblowing a flute. As a bonus, the hearing apparatus need not be especially sensitive to sounds outside the amplification band; it might even incorporate a sort of bandpass filter with the resonator.

End result: people who don't hear especially well in general, but can hear each other speak with amazing range and accuracy.

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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 communication. Speaking loudly is very hard on our biology, so we would likely not rely on it at all. The obvious result of this will be the spontaneous invention of sign language.

To see what that would be like, one can look to deaf communities. As a hearing person, I find it incredible to see just how many things they can do that I naively assumed required hearing. For a lesser experience, one could look at the TV show "Switched at Birth." The deaf community has very complicated opinions about the show (especially since the actress playing the lead deaf girl is not actually deaf), but it's the first mainstream show which prominently featured the deaf community and ASL, so they generally admit that it's a good introduction for those of us who know little about their world. It definitely functions to shake up misconceptions!

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I'd imagine that they'd build double skinned shield walls to deflect the noise from waterfalls. The most expensive parts of the city would also be the quietest, while the slums would be where the sound protection is weakest or right by the walls where there is less light.

I'd also imagine that the Palace would be built on the spar of Rock that causes the river to split as both a status symbol as well as providing a fortified position at the most vulnerable place for the city (a creature could be carried down steam onto the rock with minimal stearing by a minion).

As others have suggested, the local language will probably also include large components of sign language for use in the louder parts of the city.

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First off: brainstorm

  • higher ranking people would be in the middle of the city
  • lower on the edges
  • thick walls not only to keep monsters out but for sound suppression
  • cotton would be grown to make earplug like things
  • communication wise they would use sign language

Making sense of it:

the first 2 bullets are straightforward, quite would be a luxury in a place like this. the 3rd is also straightforward. the 4th is stretching it a bit but the civilization would be forced to make it. the 5th is also straightforward although i suppose it wouldnt be needed everywhere.

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