(or: how big of a piece of land does one need to not hear any neighbors under normal conditions?)
yes, i know how far sound is audible depends on MANY factors, including temperature, humidity, time of day, ambient noise levels, things in between the noise and the listener, etc.
but… in general, how far does a loud conversation/party carry at night?
the point of my question is this: how far away do you have to be from a group of people (maybe 5-10 people strong) having a moderately rowdy party (stereo is on, but we’re not talking quite at twin subwoofers and a 1000 watt amp at full-bore) and have peace-and-quiet? you have line of sight between source and listener.
would sitting in the middle of a 5-acre-square tract of land (i.e. being 500 feet away minimum from the closest possible source of sound) be enough? 10 acres? (1000 feet?) 20 acres? (2000 feet?)
just trying to get a good sense of how far away someone has to be to have “piece and quiet” under the vast majority of circumstances.
On a quiet night in Pyongyang, I could easily hear things happening perhaps 1km… maybe 1 mile, away (like a car door closing hard or a baby crying etc). I was above the 20th floor and the building was in a wide open area (on an island in the river). It’s a very quiet city… from a peace and quiet point of view nothing comes close.
There’s no simple answer because it’s not just a simple physics question.
I can tell you from experience that with the wind in the right direction a loud party of the type you describe can literally wake the neighbours over 2 km away, even with no line of sight. With line of sight and on a cold night I would guess you’d need at least 5 km to be sure of not waking the neighbours.
Of course that’s not the same as not disturbing the neighbours. Again from experience I can tell you that the sound of a .22LR is plenty loud enough to be annoying at a distance of around 5km. Though probably not loud enough to wake somebody up it’s plenty loud enough to stop them from getting to sleep. I’m guessing a drunken party would be making comparable noise to a .22.
A large part of your problem is that as the ambient artificial sound level decreases the relative loudness of any disturbances increases. So sounds that your mind will simply filter out in a city environment become loud enough to keep you awake in remote areas. So while a party 2 km away in a city is unlikely to even be heard over ambient noise, the same party in a rural setting will get you complaints from the neighbours. This is the sort of thing that Desert Nomad is reporting. There’s no way you could hear a door slamming a kilometre away in a normal city, but take away all the ambient noise and…
To have “piece and quiet” under the vast majority of circumstances I would guess you’d need >7km distance.
What the hell were you doing in north korea? And how did you escape your 20 story island fortress tower on a river in a city where everyone (and the crickets) is dead?
That’s pretty much the answer I get. If you double the distance between yourself and the source of a sound, the sound intensity goes down by 6 dB. If you want to go from the sound level of a loud party (which I estimate to be around 80 dB at a distance of 1 metre) to sound that’s actually below the threshold of human perception (defined as 0 dB), you need to get about 10 km away. If you only want it to be as quiet as, say, rustling leaves or breathing, you can knock that down by a factor of four or so; this would require you to be at the center of a 5000-acre tract of land. A 500-foot separation would only get you down to sound levels about as loud as an average television set or a loud conversation.
Of course, this is all assuming no sound absorption, direct line of sight, still, dry air, etc. But you knew that already.
which is crazy… even a row of bushes will substantially absorb sound, plant some trees, position your house with hills surrounding it and build it with decent walls and you will have peace and quiet with 50 acres or so…
I’d like to echo (heh) the assertion that sound-absorbing materials can make a huge difference.
Years ago I went to White Sands National Monument early on a cool fall morning. The dunes are composed of gypsum sand.
There were lots of tourists and squads of feral children roaming the parking lot, slamming car doors, calling out to one another. I walked up a dune and down the other side, and then a few more yards around a corner, and stopped. The silence was nearly total; the occasional loudest sounds from the parking area were muffled and distant, and all the rest were replaced by the stirrings of dried grass tufts in the mild, changing breeze. No other humans were visible here, and the rippled sand was marked only with the tiny tracks left by nocturnal desert animals.
It was as if all those people making noise disappeared, and I felt very solitary. The experience was strongly affecting. It seemed spiritual, but I’m sure the sound-absorbing properties of gypsum had a lot to do with it.
There are a few specifics we can be pretty sure of.
Dense materials do not couple well with gasses. While sound will travel just fine through steel or through air, when you try to pass it from one to the other, much of it will be reflected. I think it is like reflection of light as the index of refraction along the path changes, which is the mechanism whereby drinking glasses don’t vanish from sight. I think acoustic impedance takes the place of index of refraction.
Composites having many internal interfaces will transmit sound poorly. Sand dunes are like this. If they have high porosity, a large fraction of the sound can enter, as it is traveling through the air portion of the composite. But it gets bounced around and absorbed inside. I think this is the idea behind the foams used to make walls for anechoic chamber walls.
Sound travels by line of sight, on a scale larger than its wavelength, and including in situations where it reflects cleanly. Very long wavelengths like thunder will travel pretty well around corners on a length scale of a few feet, because on a scale smaller than its wavelength sound is just the ambient pressure changing in a noninertial way.
Last, sound does not travel far in straight lines through air in a gravitational field. Meaning, here. The air density has a vertical gradient, getting thinner (less dense) with altitude. That means sound on a horizontal trajectory will gradually start curving upward, as the lower edge of the waves travel a little faster through the denser air and steer the wave upward. What you hear at a distance is not only diluted by the bigger area of a sphere with that radius, as light would be, but it is also lensed outward by this gradient driven divergence. This makes the volume of sound spreading through the hemisphere of air above flat ground fall off at a steeper than r^2 rate for listeners near the horizon.
So if a tree falls among a composite with internal interfaces of varying acousting impedences in the presence of an exceedingly strong gravitational field around a corner wider than the frequency’s wavelength, does it make a sound? Well, punk?
I was on holiday. The hotel I stayed in had a fantastic view over the city as it was on an island more-or-less by itself in the middle of the river. Most nights, I would spend 20 minutes or so just looking out the open window - amazing how quiet it was… like the middle of a desert.
