# 176 dBA SPL ?

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#### mrfeedback

See this for some unintended humour.
The article mentions the Rolling Stones attaining 176 dBA - Is this possible ?.

Eric.

#### cocolino

All I can say to this article stands below - the other I don`t know
(but likely nobody ever has heard a 176dB sound wave actually, at least not longer than for a fraction of a second - otherwise I guess he/she would be completely deaf forever or maybe even dead).

#### roddyama

Hi Eric,

Let look at this from the aspect of acoustic power and the electrical power required to produce 176db SPL?s. If you have an output of 1 acoustic Watt (1aW) into an average reverberant living room, you create about 115db of SPL at a listener 3 meters from the source (this is a rough approximation, but realistic). If we give Mick the benefit of the doubt and say he has found very efficient speakers with an efficiency of 10%, it would take a 10 Watt amp to reach 115db SPL at our listener or 1aW output.

Now Mick was said to produced 176db - 115db = 61db more SPL than we did in our hypothetical living room. That is doubling our SPL 21 times = to doubling our output acoustic power 21 times. Therefore, for Mick to have produced 176db in our living room, he needed to produce 2.1MaW. The 10% efficient speakers he found would have required 21 Mega Watt of amplification, if the concert were performed in our living room!

I would say this is a bit of a stretch to make the point of the article.

Rodd Yamas***a

#### JBL

It is possible to measure 176 db from a speaker.

Spl vary inversly to the square of the distance(I think)

So iy you get very near to a horn loaded thweeter it's very easy to measure very high spl.

Beign infinitly near a speaker would mean an infinite spl

#### NU_NRG

According to this website, Someone got to a MAX SPL of 174.9 dB !

Could it be true?

What system could do so much noise?

how many ppl were killed on that day?

Simon

#### cocolino

The 10% efficient speakers he found would have required 21 Mega Watt of amplification
Hi Rodd, I don`t want appear to be hypercorrectly but according the following actual formular for half space radition, there are a couple of megawatts missing in Your calculation :

SPL(db) = 112,2 + 10log(no*Pel) - 20log(r)

where is:

no = efficiency (10% = 0,1)
Pel = electrical Power (Watts)
(no*Pel) = Pac (acoustical Power)
r = distance (meter)
SPL(dB) = 176

according to this, for 176db SPL @ 3m distance in Your living room and 10% speaker efficiency, Mick would has to upgrade his amps somewhat to 210 megawatts (of course that`s frequency dependend also and due to low frequency room boost he could save a couple of megawatts)
Anyway, You might consider bracing Your room walls and to improve the line power distribution a little bit before he plays.

#### mrfeedback

Loonies Unleashed

It was meant as a tongue in cheek question.
When I saw the article I did some quick mental calculations, translated these to outdoor or stadium venue and decided that this evangelist fanatic is rolling in it.
Did anybody read the rest of the article - this fanaticism concerns me somewhat.
I do remember reading of the US underwater soanar project that is generating something like 150 dBA spl (?) - hence the concern for the welfare of marine speces.

Eric.

#### roddyama

Hey Christoph,

Yeah, your probably right. I seen the thread when I was at work and tried to get one in from memory. You know, when you start to get old, the first thing to go is the memory. I can't remember the second thing to go?

Anyway, I thought I seen one of those 200MWpc pro-amplifiers go on eBay the other day for less than \$200. I also heard that Deep Purple used 100GWpc amplifiers,... BRIDGED!! Although, they did loose some of their damping factor by running in bridged mode. That's why their bass was always so "boomy" in-concert.

Hi Eric,

I did glance over the article. These guys are out there! Be afraid, Be Very Afraid.

SEX&DRUGS&,... ?? Oh,... Sorry. Someone's already got that one.
Rodd Yamas***a

#### specialx

NU_NRG said:
According to this website, Someone got to a MAX SPL of 174.9 dB !

Could it be true?

What system could do so much noise?

how many ppl were killed on that day?

Simon

Tis very true
Remember a car cabin is a lot smaller than a concert hall or your living room and trhese guys don't go after quality by any means, and their cars are heavily modified with 1inch plexiglass and interiors made from MDF to increase stiffness and thus not lose pressure. They have multiple arrays of speakers with multiple arrays of Class D amplifiers with multiple arrays of batteries and 1F capacitors etc etc.
I have seen one car in my local area pull off 151dB with 2 15inch subs in a 6cubic foot enclosure. Admittably it sounded horrible but you could feel it shake your body
If you read the rules and stuff for the db Drag racing you will see the microphone is located in the same position for every persons run, I can't remember the exact location, but however, it allows the use of bass loading etc to focus the SPL in one point of the car's cabin. Most people also run just one sine wave of the peak-volume frequency of their system to get even more SPL.
My friends sisters has a \$2000 AUD system which can run 137dB consistently, so it proves it isn't very hard. As for sounding good though, they are @\$#%... but good fun
The mate mentioned above had a Cerwin Vega Stroke 18inch with a Rockford Fosgate 1100a2 amplifier. It was bridged and ran into the cerwin vega double voice coils which were paralelled.
I sat in the back seat while testing a bass track I made with Cooledit and I had a sine wave sweep from 150Hz -> 0Hz over 1 minute.
On certain frequncies I could barely breath because the bass was shaking my isnides so hard. It was awesome yet freaky.

-Mike

#### griff

A couple sealed 15" Brahmas can reach 145's in an SQ setup.

#### Dirk

Hi all,

There is a very old article in the JAES (I could look it up for any interested) on producing very high SPL's, for simulation of the sound pressure levels in the Apollo program
It includes a chart of the SPL vs. distance during the launch of a Saturn 5. It is said to produce 50M acoustic watts during takeoff!

Regards,
Dirk

#### Circlotron

Nitromethane-assisted noise.

The noisest thing I have ever heard is a top fuel dragster making 5,500 hp. This would have to be the most evil sounding machine ever. Here's a 5000 hp example that measures at 164.8 dB at 1 metre in *open air* not inside a closed room or vehicle. http://sxaudio.com/ Click on logo.
Notice here some sensible people are holding on to their ears to stop them being blown clean off! http://www.webtec.net.au/~nitro/
Pic of 164.8 dB jigger below.

GP.

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• gmengine.jpg
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#### Mark Tinley

Nitromethane induced noise

I tried to follow th link to the sound charts you spoke about and couldn't find it-

I want to find a suitable microphone for recording drag bikes-

Am I right in saying I need to find something capable of dealing with 176dB at a metre?

Thanks

Mark

#### tschrama

As a side note:
My textbook teels me this:

20uPa == 0dB... 1Atm = 100E3 Pa so that is 194dB... this is about the maximum sinewave sound presure level you can possible measure...

greetings,
Thijs

#### mike34

tschrama said:
As a side note:
My textbook teels me this:

20uPa == 0dB... 1Atm = 100E3 Pa so that is 194dB... this is about the maximum sinewave sound presure level you can possible measure...

Thank you , i have been waiting for that !!
And if i understood it all right you have to achive TOTAL vaccum in the process of making that waveform.
Waiting for that day when someone say they play 195 dB sinus waves in a car

#### Sch3mat1c

Of course, to pull a perfect vacuum, the chamber would have to start out at zero volume and be pulled by the transducer (speaker, piston, etc.) to reduce pressure. If you say half vacuum instead, you have to only double the chamber size to halve the pressure (not counting temperature change, which I forget how much it'll change pressure..). That means the speaker cone has to move backwards (pull) the same volume as the chamber in front of it!

It's very easy to see that this is an inverse equation, and that's why very loud signals get distorted - simple matter of the pressure we are at.

However, the space shuttle can get upwards of 200dB, IIRC... (different situation: you have exhaust gasses at who knows what pressure here.) They spray water over the launch pad to damp this so it doesn't shatter the concrete!

Tim

#### mike34

However, the space shuttle can get upwards of 200dB, IIRC... (different situation: you have exhaust gasses at who knows what pressure here.) They spray water over the launch pad to damp this so it doesn't shatter the concrete!

Well i can imagine that we are not talking about normal air pressure in that area.
With all that exhaustgas and high temperature with cooling water that boils up in seconds which in it self gives a much higher desity of air/gas mix. i can belive that 200 dB is a possibility.
But i wont be the one with the instrument at 1,10 or 100 m taking that messasurement
Not sure but i think it might be harmful to your health.

#### Sch3mat1c

mike34 said:
Not sure but i think it might be harmful to your health.

And if the sound pressure doesn't blow you to bits, your consolation prize is being vaporized by the hot jets

Tim

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