I'm still developing my cyberpunk/fantasy game with emphasis on B&E action, and my current task is a complete revision of the stealth subsystem due to a general subsystem streamlining.
While I'm not really obsessed with realism, I try don't to break it unnecessarily as long as it doesn't hinder my other goals, so currently I'm researching real-world data on loudness to get at least a rough idea of noticeability of usual sounds as MP fire, walking guards and silenced pistol shots on certain distances.
Now, physics was always a weakness in my science knowledge, and especially accustics is an area where everything I know is exactly what I teached myself, without any formal education, so I need help on this topic.

So far I could gather that human beings have an auditory treshold of 0dB and that "room sound volume"[1] in the receiving room is measured at 30-40dB, so these should work as lower and upper benchmark for levels of sound pressure where stealth and notice checks make sense. (Of course, there are other measures and stats than sound pressure/dB, with varying degression over distance, but for a quick reality check for my rules dB alone should do it.)

I could also learn that sound pressure drops by 6dB for each distance doubling in the case of evenly emitting sound sources.

Wikipedia also has a quite extensive table with examples for certain sound pressure sources on certain distances, that after a quick double-check of a few entries with my physical lexica seems to be right, but unfortunately it lacks data for the sound pressure sources that I search.


Now to the stuff that I need help on:
Is there a fatal mistake accustics-wise in limiting the reality check to a consideration of pure sound pressure, or is this an acceptable simplification?

Can anyone give me data on how obstacles (e.g. walls) interfere with sound pressure degression?
Neither my lexica nor Wikipedia could inform me on that, and I'd appreciate every rough explanation that doesn't demand from me to wade through advanced accustics stuff.

Does anyone have data on sound pressure emission of the following sources?
- walking person
- sneaking person
- electric motors (especially important for stealthy recon mini-drones, which play a prominent role in the genre)
- more detailed firearms, with consideration of gun type, calibre, rate of fire and whether or not the gun is silenced
- explosions


[1] I couldn't really find a viable translation for the German legal term "Zimmerlautstärke". Generally, it's a level of loudness that's "hardly to notice" outside the emitting room, and anything above that during rest periods is considered as regulatory offense.

I kept researching a bit today, and at least I've got some useful data on rifle and shotgun calibres: http://www.frfrogspad.com/miscelli.htm#sound
While it's a private homepage, at least an actual book is cited as source, so there are good chances that the data provided is accurate.

On the same page, there's also something about other calibres: http://www.frfrogspad.com/safety.htm
Unfortunately, there isn't a source cited, but as the numbers of the redundant calibres between the confirmed and unconfirmed source are very close, I'll assume that they are also accurate.

All sound pressures are measured at the shooters, so I'd assume 50cm distance on average. Measuring instead at 1m and substracting therefore 6dB from each stat, usual loudnesses would be:

12 gauge shotgun - 167dB
.308 Winchester / 7,62 NATO - 164dB
.223 / 5,56 NATO - 164dB
.44 Magnum revolver - 158dB
9mm pistol - 154dB
.45 ACP pistol - 151dB


According to the linked data, rifle silencers seem to take away 10-15dB.

Pistol silencers are hard to say, as in the confirmable tables I only have stats for vanilla 9mm rounds fired from pistols and 9mm from H&K MP5SD with subsonic ammo - so in addition to the silencer, I'd have to keep in mind the longer barrel _and_ the ammo.


Now in regards of weaponry loudness, all I lack is data on the effect of RoF and the effectiveness of pistol silencers.
The above questions on loudness of walkers, sneakers, electric motors and explosions, as well as those on the effect of obstacles are yet unanswered, too.