Posted by Ralph Staub on May 05, 2002

Actually, that number is not 14, it's 2 to the 14th power which is 16,384. So take the amount of power it takes to reach 128dB @ FOH, multiply that by 16,384. If it were a very small church and you put in 10,000 watts, you might reach 128dB @ FOH. To reach 172dB in the same venue, you would need 164 million watts. NOW think about it.

Ralph


Posted by Bruce Gering on May 05, 2002

OK, so my math is not 100%, but my point is that 172dB is an insane amount of SPL, given that the threshold of pain is waaaaaaaay lower.-Bruger


Posted by Bob Lee (QSC) on May 10, 2002

My math was off, too. It's 194 dB SPL that the air starts to go non-linear by cavitating.

-Bob


Posted by Bob Lee (QSC) on May 10, 2002

172 dB would not be tolerable even with earplugs.

It's about the SPL where at sea level, you'd start getting cavitation--essentiall, clipping on the low-pressure troughs of the sound waves because you can't go lower than zero pressure.

-Bob

Posted by Scott Rexroat on May 07, 2002

The threshold of pain is frequency dependant; and peronaly subjective to a slight degree. 108 @ 3K is studip. 128 @ 30Hz is nice.


Posted by Barry Bozeman on May 15, 2002

Human hearing sensitivity is at least 40dB less at 30Hz than it is at 3.1KHz. One can experience pain at 100dB with a 3100Hz tone generated alone and 130dB of 20Hz is quite enjoyable.

I agree with you Scott.


Posted by dave stojan on May 05, 2002

Hi Bruger,

While it is true that it takes twice as much power to raise the level 3db, it is only perceived as a "very noticeable" change in level. 10 db is perceived as a doubling or halving of level (depending on which way you're going). There is also a corresponding 10 to 1 difference in power. Given a basic sensitivity of 102db, you would have to pump 10,000,000 watts into the speakers to achieve 172db at 3 feet (without factoring in power compression!).

Also, the threshold of pain varies depending on your source, but most of what I've seen is at 120db. This level is different from one person to the next of course, but 120db is it for the "average" person. Miffe has his closer to 130db. 120db to me doesn't "hurt", but it begins to feel like someone is pulling a string through my head in one ear and out the other. That's a special feeling!

172db is probably space shuttle launch volume. Next time I'm poking around nasa's website I'll do a search.

All the best –Dave


Posted by Bruce Gering on May 05, 2002

Hey Dave,

I came up with that figure because I wanted to be on the high end of the curve for pain threshold, giving 172dB the benifit. My level of comfort is around 102-105dB. That's about what I like to hear at FOH. 115 dB is about all I can take without plugs, which I usually put in when the band stops if the club has an in-house dj for breaks.-Bruger


Posted by Timothy J. Trace on May 05, 2002

www.digido.com/shuttle.html

www.ghg.net/pss/www/cd/facts.html

www.live-audio.com/messages/archive3/73768.html


Posted by dave stojan on May 05, 2002

You are a veritable fount of information! Thanks again for the links!

All the best -Dave


Posted by Jim Travis on May 05, 2002

Maybe the sound board is inside one of the speaker cabinets?

ShowPro MIDI Software for Live Sound


Posted by Chris Hindle on May 05, 2002

More like "Maybe the sound board is tied to the tower where the Space Shuttle gets launched ?"

Chris.