Petrol Fumes and microphones?

[ktime]

Hi all. Recently I have been recording some ex-soviet oil tanks (Martin Kay « Martin Kay) in Armenia, and am wondering about the potential damage it could be doing to my mics. I'm using some dpa 4060's for the job because I can soak them in distilled water afterwords. and they still seem fine. but I am now considering using some less noisy omnies.

so I'm just wanting to know what the deal with gasses and mics are?

the fumes are so strong in the tank that it is not possible to go inside my self for more than 30 seconds, and from the top of the tank (from where I am dropping the mics down) the fumes are shoot out like a hair dryer.

any info on the matter would be greatly appreciated

Marty

[sonare]

Contact DPA--

[JEGG]

Originally Posted by ktime

so I'm just wanting to know what the deal with gasses and mics are?

This is an area that I'm interested in as well, so I hope you and others report what you learn from manufacturers.

I could also see relevant information coming from EFX people, and also trades people who use mic's to measure/evaluate products and environments. I'm wondering who the mic/transducer suppliers are to those markets-perhaps B&K and Gefell. Perhaps the folks from Josephson might be of help. I'm also wondering about microphone powering and volatile environments.

Since manufacturers use different materials and methods in polarizing mic's, I suspect there will be an interesting variety of answers-unless manufacturers resort to something like "we don't advise using our microphones in those situations."

'Sounds like you do interesting projects, BTW........

[audibell]

First, don't change batteries, turn 48v dc on or off or use any electrical or iron (sparking) tool while tromping around inside those tanks.
Do you have a confined space entry procedure in place, which includes a tag line attached to your body (before it becomes a corpse) and some kind of compressed air breathing set outside, ready to be used to come get you when you exceed your exposure threshold?
Gasoline is a mixture of many components, most of them so volatile that just the cold hairdryer you referenced, will evaporate the VOCs (volatile organic compounds) and leave little or no residue on the diaphragm. I wouldn't submerge the mics in water until after the job is complete.
The greater problem to your health is that older tanks filled with vapor will also rust on the inside, which consumes some of the oxygen inside the tank, lowering it past the 19% considered marginally safe for humans. It's not just the vapors that will harm you, it's lack of O2.
I presume you're after the reverb inside these tanks so a starter pistol is not the impulse of first choice. Perhaps a clapper stick will be enough.
If you get permission to take the manhole cover off at the ground level of the tank and place a compressed air driven fan in the aperture, after about a week, it will be safe to enter, unless there's a two inch lake of petroleum tank bottoms still inside.
If you're stuck with the tanks as they are, just an open port on the roof through which you're dropping a mic cable, wait until night when the steel tank shell cools and the vapor stops rushing out and air starts sucking in. Once you have the mic at about 10 feet off the tank bottom, have a colleague smack the side of an uninsulated tank with a BFH (big fxxxxxx hammer) for your impulse. Record your response and process out the bang later. If you wait for equilibrium, around 2 am, there won't be much air rushing noise at all. There might be condensation drips which you can remove with NR software.
Tell us more about the situation.
Rgds
WalterT

[ktime]

WOW, thanks Walter. That would have to be the most detailed response to a question that I have ever posted on Gearsluts - much appreciated.

For some pictures and sound recordings of the tank please see (Martin Kay « Martin Kay)

The tanks have been abandoned since 89, around the fall of the soviet union in Armenia, as they were no longer an economically viable/capitalist way to heat a city. There are approximately 4 man holes which are permanently open, and roughly about 1 cm of of a muddy oily residue with a few puddles of oil scattered on the ground. (see picture)

As there is an opening at the top, I will definitely not be entering the interior of the tank my self, although I was considering sticking a couple of boompholes through the man-holes to compare the sound at the bottom and sides of the tank to that of the top center.

I am interested to hear your reason for only soaking the DPA 4060s at the end of the job as opposed to the end of each day, does soaking the diaphragm in water wear it out?

Also thanks for the recommendation and tips on capturing the impulse. I had not considered this, but can see how it would make for a very interesting acoustic postcard! The main reason for recording the tanks is to capture how the surrounding environmental sounds I.E wind, rain, passing trains etc. are processed through this reverb. I am finding that the 4060s are a little bit noisy to capture these general amiences of the tank, and I have SERIOUSLY been considering dropping my sennheiser mkh 8020 to capture the extremely rich bass tones the tank produces, but so far it has been to hard to bring myself to expose such an expensive mics to the fumes. - but it is very tempting.

I might also look at somehow submerging my hydrophone in the muddy oil with the assistance of a few buckets of sand and water. and see what recording I can get from this.

Once again Thanks for your help and I look forward to hearing any more tips that you have to offer.
marty

[John Willett]

For volatile environments, Sennheiser produced the optical microphone. This can be used in places where there are explosive gasses, etc. and can even be used inside a CAT scanner.


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[JEGG]

Didn't know that. Being the curious sort, is there a link for that and any other bespoke goodies Sennheiser has built for specific applications? I seem to remember an old mic for measuring artillery or some sort of thing? (Measuring *what* about artillery I don't remember.)

I am a bit interested in the optical mic.

[John Willett]

Originally Posted by JEGG

Didn't know that. Being the curious sort, is there a link for that and any other bespoke goodies Sennheiser has built for specific applications? I seem to remember an old mic for measuring artillery or some sort of thing? (Measuring *what* about artillery I don't remember.)

I am a bit interested in the optical mic.

The Optical Mic. should be on the Sennheiser website. If you can't find it I'll have a look when I get home. It is a normal product and not a bespoke device.

The "Artillery" mic. was the MKH 110 or 110-1. These were omni mics. in the same vintage as the MKH 406.

The 110 had a flat response down to 1Hz and the 110-1 went down to 0.1Hz. The military used to bury an array in the ground and used them for gun ranging. No more left and existing ones cannot be repaired as there are no more spare capsules available.


Posted via the Gearslutz iPhone app

[JonesH]

This is a cool thread
Very high S/N ratio as well (except for my post perhaps).

[audibell]

Marty,
I viewed your pics and they are pre-1950s lapstrake & riveted, non-insulated, gasoil storage tanks. They may be iron rather than steel and, rather like 1980s Moscow taxis, their design might be 1940s but they may have been built much later, though I doubt it - oil has been exploited throughout the Caucuses since before WWI.

We'll leave the "economically viable/capitalist way to heat a city" for another forum.

If the tanks have been open for months, the volatiles (light-ends) have probably long since evaporated but areas of low O2 will still be encountered until you forcefully exchange the air inside with fresh exterior air. So be very careful.

And if you're going to talk a brave local into "penetrating" the tank, have him catch a clothes-line you drop from the top center and lead it out through one of the manholes. That way you'll have a running line with which to carry & position a mic/cable at any height/place between the two openings, from the exterior.

Warm distilled water will probably have little effect on the diaphragm or wire weave but the heat which you will probably apply to thoroughly dry it out after each day's exposure to these hostile conditions will cause expansion and contraction of the various metals inside. Those mechanical excursions might create some electrical noise or even intermittents, so I would be using rat shack lavaliers or cheap LDCs for this, unless a rich Uncle is paying for the B&Ks.

All our little jewels are just expensive Black & Deckers. You've traveled 5,000 miles to record some WPA-type stuff - so use what you brung and any effects noticeable in later years can be proudly pointed out as battle scars on an honorable veteran bit of mic-age.

I would draw the line at submerging a hydrophone in dirty, tank bottoms though. because as the light ends are mostly evaporated, the remaining tars, waxes and sediments carried in under pressure, will be almost impossible to remove from within the microphone's labrynth internals without strong solvents. Ethylene di-chloride or warm toluene, while workable, will undoubtedly soften/delaminate the plastics inside. Dismantling the mic so as to use a fine squirrel hair brush is also a job best left to Sennheiser elves.

If you can talk local ethnic singers to perform some Armenian Christian or Eastern orthodox church chants into the four open manholes and record the reverberent mess from inside with the drop mic, that would surely be a unique and probably unreproduceable cultural artifact!

I'm wondering how a non-flat response at 3 or 4 Hertz would be manifest; on the artillery mics, I mean. I knew a Russian Bass once, who could sing so low he was just clicking like a dolphin but as he started his ascent back up the scale, it began to have tonality around 28 or 30.

BRgds
WalterT

[John Willett]

Originally Posted by John Willett

The Optical Mic. should be on the Sennheiser website.

It's HERE.