Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels. The
majority of the energy is below 12 kHz in the recordings I have. I
don't believe exact replication of the sound fidelity is critical for
my testing, but the amplitide is important.

Also, what might I use to keep the sound from getting too loud outside
of my test room?

Thanks,
Edward

"edward" wrote ...
I am testing a sound protection and recording system
that will withstand very loud sounds. I need to test in
a sound field that is at least 135dB or better. I'm
performing real world testing at 135 to 153dB SPL
and need to simulate those levels in a room in my
office building.

Dosen't seem practical to attempt this in "a room in my
office building". Unless the building is scheduled for
demolition soon and you conduct the tests only at night
or weekends when others are absent. :-)

Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet
aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels. The
majority of the energy is below 12 kHz in the recordings I have. I
don't believe exact replication of the sound fidelity is critical for
my testing, but the amplitide is important.

There are a number of manufacturers/vendors of large
speaker systems which are used in live music events
(i.e. head-banging rock concerts) Some of their more
heavy-duty industrial-strength products may be able to
produce these sound levels in a small enclosed space.

The people over on another newsgroup deal with these
speaker and amplifier systems every day. Check out...
news:alt.audio.pro.live-sound Beware, they can be a
rough crowd, but there are several experts there.

Also, what might I use to keep the sound from getting
too loud outside of my test room?

I doubt there is anything practical you can do in existing
construction to even eliminate the problem of the SPL
causing damage to the structure. Trying to contain it without
a foot or two of solid concrete and/or lead seems impossible.

Why not investigate the facilities that are already set up for
this kind of experimentation? Seems quite likely that there
are several across the US and in many western countries.

In article .com, "edward" wrote:
Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels. The
majority of the energy is below 12 kHz in the recordings I have. I
don't believe exact replication of the sound fidelity is critical for
my testing, but the amplitide is important.

Also, what might I use to keep the sound from getting too loud outside
of my test room?

Thanks,
Edward

You need to build a sealed chamber to contain the equipment. The
exact frequencies? There could be extreme low frequency components
that might be hard to deal with . Some powerful mid to high range driver
should work.

greg

In article , (GregS) wrote:
In article .com, "edward"
wrote:
Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels. The
majority of the energy is below 12 kHz in the recordings I have. I
don't believe exact replication of the sound fidelity is critical for
my testing, but the amplitide is important.

Also, what might I use to keep the sound from getting too loud outside
of my test room?

Thanks,
Edward

You need to build a sealed chamber to contain the equipment. The
exact frequencies? There could be extreme low frequency components
that might be hard to deal with . Some powerful mid to high range driver
should work.

I was just pretending to hear what it sounds like. I have some recordings from my
camcorder. One set, I was standing to the rear, off to the side about 50 feet away from a dragster.
I didn't have to hold my ears, yet standing in the crowd off to the side, the
high frequency whinning makes you cover your ears normally. My camcorder
plays much better audio than most, but it still was clipping the input amplifier
Knowing the spectrum and its levels, is critical to judge what is required for reproducing
the sounds.

greg

In article , (GregS) wrote:
In article , (GregS)
wrote:
In article .com, "edward"
wrote:
Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft

You might be able to get the levels and relative bandwidth using
a horn driven by an air gun of some sort. I'm crossposting this
message.

greg

In article , (GregS) wrote:
In article , (GregS)
wrote:
In article , (GregS)
wrote:
In article .com, "edward"
wrote:
Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft

You might be able to get the levels and relative bandwidth using
a horn driven by an air gun of some sort. I'm crossposting this
message.

Group at

alt.sci.physics.acoustics

greg

Thanks to All,
You've pointed me in the right direction.
And I'll plan on doing my testing out in my barn
rather than in my office. I'm close enough to
an airport that noone will be certain where
the sound is coming from.
Edward

In article , Per Stromgren wrote:
On 26 Mar 2006 14:51:20 -0800, "edward"
wrote:

Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges.

Perhaps you can get that sort of SPL:s inside a loudspeaker enclosure?
I know that the levels inside is a lot higher than on the outside, but
not how much higher. 10-20 dB is my educated guess.

That sound kinda sounds like my oil fired furnace, without the bearing
whine. Also a little like some torches I've heard.

greg

Per Stromgren wrote:
On 26 Mar 2006 14:51:20 -0800, "edward"
wrote:

Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges.

Perhaps you can get that sort of SPL:s inside a loudspeaker enclosure?
I know that the levels inside is a lot higher than on the outside, but
not how much higher. 10-20 dB is my educated guess.

The Bruel & Kjaer 4220 pistonphone calibrator
achieves a 127 dB SPL in a volume of about 19
cm^3 using nothing more than two pistons about
4 mm in diameter with a total peak-to-peak ex-
cursion of all of 0.5 mm (that's a displacement
volume of 6 billionths of a cubic meter, smaller
than most 1" done tweeters), all powered by a
9-volt battery. The total displacement ratio is
about 0.033%. To get to anSPL of 135 dB would
require a change in displacement ratio only about
2.5 times that, or all of about 0.08%.

Achieving very high sound pressure levels at one
specific point is not very difficult at all: it requires
simply that the pressure change at that point by
the requisite amount. You want 135 dB? make the
air pressure there chage rapidly enough by only
0.08%, and you have 135 dB.

So, inside a speaker enclosure, all you need to do
is change the volume by 0.08% at the right frequency
to get an SPL of 135 dB. Say you have a speaker with
an internal volume of 1 cubic foot, about 42 liter. You
have to change its volume by 0.08% of that, or about
0.034 liters, or 3.4 x 10^-5 cubic meters. Using a 10"
woofer, with a piston diameter of, say, 22 cm, you
need only a whopping excursion of 0.9 mm, a wee
more than 1/32", to get there.

Of course, there are some caveats: for this to work,
the largest dimension of the enclosure needs to be
substantially smaller than the smallest wavelength,
so the the pressure is essentially the same every-
where in the enclosure (for a 1.5 cubic foot box, this
limits the experiment to about 100 Hz or lower), the
enclosure has to be sealed and essentially loss-
less, and the item being subjected to the sound
has to, obviously, fit in said enclosure.

Enclosure too small? Make it bigger! And therein lies
the rub: The total displacement RATIO will remain the
same regardless of the size of the enclosure, so that
the displacement volume must go as the total volume.
Make it the size of a room (42 cubic meters, a room
only 8' high, 12' wide and 16' long), since it's 10,000
times the size of our enclosure, requires 10,000 times
the displacement volume to achieve 135 dB at every
point in the room (again, assuming the room is
sealed, etc).

Or get something that plays pretty loud, and just get as
close to it as needed. A speaker that's capable of
producing 105 dB at 10 meters will produce 125 dB at
1 meter., and 135 dB at about a third of a meter (1 foot)
from the source. Again, there are some constraints, the
neat inverse square ratio works fine untilm you're in the
near field, defined here as the point where the distance
from the driver is no longer substantially larger than the
driver itself.

There are definitely some restraints in my testing configurations that
lend themselves to this approach. At present, I have a system that can
generate about 128dB. During the test, I am wearing a protective
helmet, a lexan mask, ear muffs, and ear plugs. I stand at about 1 foot
from two speakers. My amplifier is only a 125W/channel Sony unit, so I
know I can go farther. Theoretically, I could make an enclosure that
would allow me to place just my helmeted head into a box mounted on the
ceiling. One aspect that is a bit unusual about the actual noise
environment around the jet engines is that the sound pressure wave
tends to come primarily from one direction.

Edward

"edward" wrote in message
oups.com...
There are definitely some restraints in my testing configurations that
lend themselves to this approach. At present, I have a system that can
generate about 128dB. During the test, I am wearing a protective
helmet, a lexan mask, ear muffs, and ear plugs. I stand at about 1 foot
from two speakers. My amplifier is only a 125W/channel Sony unit, so I
know I can go farther. Theoretically, I could make an enclosure that
would allow me to place just my helmeted head into a box mounted on the
ceiling. One aspect that is a bit unusual about the actual noise
environment around the jet engines is that the sound pressure wave
tends to come primarily from one direction.

Edward


do not most sound/noise sources come primarily from one direction?
discounting echo/reflections.

"TimPerry" wrote -
do not most sound/noise sources come primarily from
one direction? discounting echo/reflections.

At those kinds of SPLs, who would notice? :-)

"Edward" didn't mention the SIZE of the desired test area,
but it is certainly easier to develop that kind of SPL in a
small enclosed space than in a large area, particularly
outdoors (except with an actual jet engine, etc. :-)

Peter Larsen wrote:
edward wrote:

Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels.

This question was vaguely hinted at by Greg, how did you make the
recordings and how did you ensure that nothing clipped when making them?

Edward

Kind regards

Peter Larsen




Four, maybe three, 70's vintage Marshall stacks and one finely tuned
fender strat should do the trick.

(sorry I couldn't resist)

edward wrote:
Hello,

I am testing a sound protection and recording system that will
withstand very loud sounds. I need to test in a sound field that is at
least 135dB or better. I'm performing real world testing at 135 to
153dB SPL and need to simulate those levels in a room in my office
building. Can someone suggests a combination of components (speakers,
amplifiers, etc) and manufacturers that can get me close to these
ranges. The sounds that I am wishing to replicate are from jet aircraft
engines. I have make recordings at 44HKz, but am unclear about how to
play them back at levels similar to the actual recording levels. The
majority of the energy is below 12 kHz in the recordings I have. I
don't believe exact replication of the sound fidelity is critical for
my testing, but the amplitide is important.

Also, what might I use to keep the sound from getting too loud outside
of my test room?

Thanks,
Edward

-
Perhaps a little thinking outside the (speaker) box would help. The
most efficient means of producing extreme and sustained SPLs would be a
compressed air or steam whistle, which would be far cheaper than any
electronic approach. It would require some capacity for metalworking for
fab and tuning, however.

--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.