This debate came up with a friend earlier. At what levels does noise become lethal to a human? I have found numerous examples of various levels of sound pressure, but cannot find anything suggesting at which point a human will die from exposure, and so I turn to Dumpshock in hopes of someone having greater knowledge on the subject than myself.

So, my question is, at what level with short-term exposure (say, 1 minute), can sound pressure kill the average human. Keep in mind a stun grenade is a near-instantaneous blast at 170-180 dB capable of incapacitating a human for up to a minute.

Also, what is the drop-off rate of sound pressure (ie. if 150 dB at source, what is it at 100m? 300m?) at sea level & 2,000 feet, given average atmospheric conditions?

A few examples of various sound levels (in Decibels)
~250 dB - Nuclear explosion
180 dB - Rocket engine
170+ dB - Stun grenade
160 dB - Turbojet engine
140 dB - Loudspeaker rock concert
130 dB - Threshold of pain
~120 dB - Hearing damage (short-term exposure)
90 dB - Loud speech
~85 dB - Hearing damage (long-term exposure)
70 dB - Usual talking
10 dB - Calm Breathing

With a flash bang it's also the bright flash and the shockwave.

This text on nukes says 400 kPa overpressure is 100% fatal. I have no idea how to convert that into dB, or if you even can.

That may prove useful, but for now I cannot find a converter.

I would also like to point out that on a modern stun grenade, the shockwave is created entirely by the sonic blast. Flash-bang's have the light for additional disorientation, not damage.

I presume that "at source" is actually at some standard distance from the source? (Hard to talk about the volume of the sound inside the speaker or inside the grenade.

As I understand it, after that, sound energy dissipates as the square of the distance (a factor of 4 for every doubling of distance.)
And every 10 dB is a factor of 10 in energy.
So, roughly, 10 dB every time you multiply the distance by 3.2

Joel

...many years ago I was at the Seattle Bumbershoot festival when they were setting up a stage for the next act. While connecting the sound system there was a momentary strong resonant subsonic feedback which made all of us in the area nauseous and even caused several people to actually toss their cookies.

After that experience I delved more into the destructive effects of sound (I had already studied acoustics for pipe organ design) and developed a segment of history for my SF story called the Great Sonic Wars in which sound projectors and low flying hypersonic drones were employed as planetary weapons. [© Amber House Art Works]

As a rule of thumb in my classes (I'm minoring in electronic music among other things), 180-200 dB is considered "instant death," no matter what the frequency. The US Navy tried some new sonar system at those levels and a bunch of whales and dolphins washed up on shore with cerebral hemorraging; a nasty bit of press as I recall.

It's about 200-ish dB in air.

The M84 Stun Grenade is about 175 dB.

"The decibel scale, the basic sound measurement, runs from zero
which is the threshold of sound to 150 which is considered a lethal level of sound."

HUMAN RESPONSE TO SOUND – BACKGROUND INFORMATION
http://www.co.mendocino.ca.us/planning/Gen.../02Backgrnd.PDF

Thing is, there are alot of variables, and hard data on the subject is probably difficult to come by. I mean, it's not like you can run clinical tests--and if you did it would be unwise to publish your findings. Failing that you have to either guess or wait for some dude to be killed by sound while wearing state of the art audio analyzing equipment.

Also, I'm not sure how or if this affects the actual decibel level, but the frequency of the sound can have a big effect too. Seems like db's might be the wrong thing to look at, more a matter of air pressure or frequency.

Gotta love that hierarchy.

the average listener is probably 15+ feet away, which Should attenuate to less-than painful levels.

also, remember that it's measured in decibels, which is a Logarithmic scale, not linear.

I've been to some loud gigs in my time, but I went and saw The Drones (An australian psychedelic blues/rock band) and they were the loudest band I've ever seen. I hit that threshold of pain, easily. I actually left the room and checked for bleeding.

Well, as long as we don't come close to Disaster Area Levels of Noise, all is forgiven *g*
Also: why use general sound, if there's a sonic rifle in SR? Stun overflows, so some hits are enough neh? O.o

IIRC most USN SONAR systems at the time I served when using Triple Frequency Bottom Bounce Mode of operation exterminated marine animals, except for Well Prepared SEAL Teams, it also would cause the ocean to glow. You did not want to be in the Main Access Trunk when the SONAR was in that mode either. That mode was also used as a Anti Swimmer Defense too.

WMS

Sound propagating through the air obeys the inverse square law, meaning that doubling the distance quaters the intensity. 1 bel (10 decibels) is the base-10 logarithm of the ratio between a measured value and a reference value (which can be arbitrary). Because decibel values is derived from a ratio with a variable reference value, they are totally meaningless unless you know what that reference value is. The standard reference value for sound intensity is 1 Sound Pressure Level (SPL). 1 SPL is equivalent to 20 microPascals in air or 1microPascal in water and is, supposedly, the softest possible audible sound intensity. This reference is correctly represented by the abbreviation dB-SPL. dBA and dBC are weighted subjective loudness measurements and thus unsuitable for calculating actual damage caused by sound.

Assuming that we are measuring in dB-SPL, you can calculate the value at any given distance by taking the intensity of sound at the unit distance (the unit distance is preferred because it is 1 in whatever unit you are using, thus making calculating the ratio of distances substantially easier) and performing the following conversions:

Divide the decibel value by 10 to get the value in bels. (x/10 =y where x is the initial value in Db)
Raise 10 to the power of the value in bels (10^y = z where y is the value in bels)
Divide this value by the square of the ratio of the the distance that one wants to calculate the intensity at to the distance where the intensity was initially measured (z/d^2 = a where d is the ratio of distances such that dc/dm = d where dc is the the distance at which one wishes to calculate the intensity and dm is the distance at which the initial intensity was measured provided that the distances are in the same unit)
Take the Base-10 log is this result. (log10 (a) = b where b is the ratio of the intensity of sound relative to 20microPascals in air or 1 microPascal in water at the distance at which one wishes to calculate the intensity of sound in bels)
Multiply this value by 10 (10b = c where c is the intensity of sound relative to 20microPascals in air or 1 microPascal in water at the distance at which one wishes to calculate the intensity of sound in decibels)

In other words, just use fucking Pascals you fucking jackasses. Yes, I'm talking to you, Alexander Graham Bell. I know you're dead but I don't care. You must be made to pay for making the measurement of sound intensity absurdly overcomplicated and I sir, will do it, if I have to rip your soul from the afterlife and shove it into your desiccated corpse so that I can torture you with years upon year of non-stop Yani.