How quiet is it?

[Janx]

continuing the discussion mainly because its interesting...

Noticing a sound is about differentiating from other sounds. So it's as much what isn't there as what is there. A consistent background sound can make it much easier to notice someone. Sometimes even easier than if the environment was dead silent.

that sounds counter intuitive and possibly contradictory to my experience. I've had some training in the art of stealth (but am not a ninja).

ambient or background noise will help disguise my movement, barring any accidental noises I might make.

Thus, my best walking silently in a forest with no twigs is still not perfect. If there's any extra ambient noise (wind in trees, birds chirping, etc), then I'm fine. If it's dead silent, I'm screwed.

If I step on a twig (and I do know how to walk to minimize the noise such can make), then I'm double screwed, because a twig snap tends to be sharp, and out of the ordinary of the usual chirps and rustles.

If I am sneaking through a server room, past a person's back, the noise of the fans will easily cover any of the nearly silent steps I might make. I'm not making a sudden extra lack of noise. I'm simply not adding noise.

Whats more probable, is opening the door to get in/out of the server room might change the pitch (as the sound can escape the room) to a listerner in the room (not super likely somebody wiill notice, but possible). Somebody outside the room will notice, because the sound from the server room will be audible in the much quieter space outside the room.

Additionally, psychologically, a sneaker really tries to move quietly in a quiet place. They can hear if they make the slightest noise and are extra careful. They'll even freeze, and verify there was no reaction (just because I hear the noise I made doesn't mean anybody else did as I have the greatest proximity to the sound). Conversly, in a noisier space, since I can't hear my minimal noises, I may be less mindful and am more likely to fail to mask when I do something that makes noise.

Consider I am sneaking through your house to kill you and I step on your dog's squeaky toy. The moment my foot even touches the toy, I change my posture, balance and avoid squishing it. because I am watching EVERY footstep I make and am doing so slowly.

Whereas, when I am sneaking through the server room, where you have fallen asleep while working on something, it's so noisy in there, that I may just stride on in, while taking care not to goof up, clearly not watching my steps as closely. Thus, I may knock over the stack of CDs next to the PC I am trying to get files off of.

How this translates to game terms? It might mean that ambient noise levels is a wash in terms of modelling.

 

[El Mahdi]

ambient or background noise will help disguise my movement, barring any accidental noises I might make.

Remember though, it's not just a Move Silently check, it's an opposed check against Listen - even in the real world. You can ace your move silently check, but if someone aces their Listen check, it may not matter.

For me (in the real world), it isn't about whether you make noise, it's about how your very presence affects the ambient noise of the environment.

If you were to sneak up on me in an environment with a non-varying ambient noise in the mid volume range (good old white noise, like the sound from a central air system), unless you move reeeeeeaaaaaally slow, I will notice the change in pitch of the ambient sound caused by your body - even if you didn't make a single extraneous sound yourself. (Even if you do move reeeeeeaaaaaally slow, I still have a decent chance...) I do this all the time with my wife. She'll try to sneak up on me, and do a pretty good job at not making any noise, but I'll hear the change in the sound of the air and without turning my head say "Hi Babe..." (to which she usually responds "How do you do that?!?"). However, she did get me the other day (on accident). I was in our kitchen making dinner, with a tv on in the kitchen and the a/c running. I didn't notice her when she came home from work until she actually came into the kitchen. I didn't really see or hear her either, I think I just subconsciously heard a change in the sound of the tv and jerked my head around (and there she was). She was about 10 feet away from me when I noticed her, which is pretty close for me. Scared the hell out of me...and that doesn't happen very often. She laughed for the next 5 minutes just because it's so rare for her to get one up on me like that (especially accidentally).

Now if it's an ambient environment with natural or random changes in the pitch and volume of the ambient sounds (wind, talking, music, etc.) then it gets a bit harder for me, but I can still sometimes pull it off (like above with the tv). I can probably notice someone in a constant ambient environment well over 90% of the time. In a variable environment, it's probably more like 50/50.

Incidentally, this is how stealth fighters can be detected also. Direct radar returns can be so small (depending on proximity to the receiver/transmitter) that they are usually filtered out as noise. But a supercomputer with multiple ambient receivers (monitoring ambient EM) can detect them sometimes through changes in the ambient environment. Like tracking a hole in the EM field, rather than tracking a positive return.

Just like being cued by motion visually, the brain more often passively detects things not through the presence of something, but due to a change in the environment.


Not everybody can do that, but I can. It's just a natural thing for me. I have very sensitive hearing and can naturally hear very small changes in pitch. I also have a wider than normal frequency range: 10 hz to about 24 khz - as opposed to 20 hz to 20 khz (and well above the norm for my age which is more like 30 hz to 16 khz), and an excellent spatial sense. I can quite easily hear those so called "ultrasonic" ringtones that some kids use on their phones (so adults don't hear it).

But don't just take my word for it though. Due to working in aircraft maintenance in the Air Force, I was required to have annual audiogram tests. When I retired, my low and high frequency sensitivity had dropped off a little bit from my baseline (down to as low as -50 db for extreme frequencies), but from 375 hz to 18 khz I still have a sensitivity of -90 db across the board. The audiogram testers always thought I was some kind of freak.

Despite being a drummer and working on aircraft in the Air Force, I've been able to maintain this by jealously protecting my ears. On the flight line I always had earplugs in when aircraft were running (or power units, etc.), and always wore dual protection when in close proximity (earplugs and headsets). The downside is high frequency noise like from a tv tube or other electrical appliance (motors, lights, etc.) sometimes just bug the hell out of me. It's like having a mosquito hovering by my ear.

Gamewise, this is why I give blind creatures/characters a serious bonus to Listen checks. It's as much about the sensitivity of the ears as it is the development of spacial processing in the brain. Studies show that blind people actually use the same parts of the brain for sound, that sighted people use for spacial and visual processing. They "see" their environment in 3D using sound. I've never practiced this or tried to develop it, but in a pinch I can do a pretty good job navigating by sound. If I was deprived of sight for a long enough period of time, I'm betting I could function pretty normally that way. Not that I would want to lose my sight, but if god forbid it did happen, I'd probably acclimate pretty quick. For me, going deaf would be a nightmare.

 

[pawsplay]

Whereas, when I am sneaking through the server room, where you have fallen asleep while working on something, it's so noisy in there, that I may just stride on in, while taking care not to goof up, clearly not watching my steps as closely. Thus, I may knock over the stack of CDs next to the PC I am trying to get files off of.

I would hope you would be more careful? ... I don't think the Listen rules can really take into account being a dumbass.

I thought of another wrinkle; while we usually think in terms of seeing and hearing being separate, they really aren't. It's actually impossible to absolutely locate a sound with your eyes closed as human stereo hearing is only 2D; thus, a sound at 2 o'clock to your right sounds exactly like its mirror image at 4 o'clock. I can "hear" voice sounds better if I can watch the talker.

Then there's attention capturing. Imagine you are sitting at your desk at work waiting to hear if you've won a prize drawing. Just as the results are being announced, your boss walks up and asks you about something you're supposed to be working on. A few minutes later, after he leaves, you look over at the clock and realize you missed the prize announcements entirely.

 

[El Mahdi]

It's actually impossible to absolutely locate a sound with your eyes closed as human stereo hearing is only 2D; thus, a sound at 2 o'clock to your right sounds exactly like its mirror image at 4 o'clock.

That's not entirely accurate. For most sighted people this is true, but for those with highly developed auditory processing it isn't.

"Hearing" is done by the brain and not the ears, just as your eyes aren't actually doing the seeing. It's the processing that does the hearing and seeing.

The brain determines position of sounds in a number of ways, the two most common being the difference in time between when a sound is heard in one ear before the other, and the difference in volume of a sound from one ear to the other - which is mostly how we determine a sound is coming from the right or the left. But the human brain can also determine pretty small phase differences in sounds (which is actually just timing also). And those phase differences can happen within the signal from one ear, rather than just the signal between ears - which is how we locate the position of a sound from front to back.

The outer ear acts as both a filter and an accoustic channel, with the shape of the ear helping to create harmonics and phase differences, just like an object creating eddy currents in water. The brain also uses this to determine localization of sound. The more developed this processing is in the brain, the better the persons 3D picture of the environment. That phase difference is also how sound can be manipulated to provide depth and position (front to back) even from only two speakers. The Bose Wave system and SRS processing exploits this very thing.

This processing is usually not as developed in sighted people as opposed to those who are blind - but even sighted people can develop it with practice. It's just a matter of depriving yourself of sight so that the brain is forced to adapt (however this does take significant time and effort - and No, I have not done this). In those deprived of sight, the part of the brain used for visual processing oft times ends up being subsumed for auditory processing - and it's very much 3D. But just like with sighted people, some blind people have really good spatial processing and others don't. Spatial sensing from hearing may not ever be as exact as visual location - but it can be quite good in those who have developed it, and it's definitely 3D.

The shape of each persons ear is unique to them, and the processing inside their brain is just as unique. A sighted person whose dominant spatial processing is also visual (as most are), probably wouldn't be noticably affected by the loss of their external ear (except for cosmetics), as long as the internal structures weren't damaged. But a person with a higly developed auditory component to their spatial processing would need some time to compensate. Likewise recieving a prosthetic or transplanted ear would also change the way sound enters the ear, and the brain would need time to compensate - to relearn what the phase differences mean. This is also the reason that surround sound, SRS, Bose Wave, etc., don't work the same or as effectively for every person.

 

[Janx]

I thought of another wrinkle; while we usually think in terms of seeing and hearing being separate, they really aren't. It's actually impossible to absolutely locate a sound with your eyes closed as human stereo hearing is only 2D; thus, a sound at 2 o'clock to your right sounds exactly like its mirror image at 4 o'clock. I can "hear" voice sounds better if I can watch the talker.

that doesn't sound right. I'm pretty sure humans can tell what direction a sound came in. Otherwise, I'd never hear the effect of the helicopter passing on Metallica's intro on One.

I suspect there's some blind spots, like maybe dead center in front or behind. But right or leftism seems to be exactly what our pair of ears is for.

I reckon when I'm feeling less lazy, I'll put this to the test with a chair and a victim.