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Extremely Low Frequency Environment


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I was asked by a Director friend of mine to see if I could help some of his friends discover what is happening in their immediate neighborhood. In June this year, they started getting extremely low frequency sound getting into their wooden house. The effect is that they can't sleep at night as it is at its loudest then.

When they put their heads down on the pillows there's a constant but with slight variations,very deep rumble that goes most of the night.

They suspect that a battery recycling and disposal factory about half a mile away have installed some new equipment that is causing this. The factory has been there for years and has some bad environmental history. Also they recently installed a new smoke stack that is quite tall. Underneath their house is an aquifer that is common to the area and as they very close to the sea,is affected by the tides.

I had had a walk around their property and nothing seemed to be amiss.I had also had a listen across the road from the factory and noticed quite a large bottom end to the sound coming from it.

So I set up inside their house with a SD 302 and my Mk41 without any bass cut on a mic stand in a PSC mount. This was during the day and heard the usual traffic and heavy trucks etc. I closed down all the windows and doors to eliminate the higher frequency sounds and was then satisfied that the only constant sound there would be, would be the ELF if it was there.

I turned the 302 on and set it to my normal dialog setting and the meters were flicking along fairly low but constant.....so I upped the level to full on the gain control and adjusted the fader to give a constant mid range reading on the meters. I did several tests around the various rooms and found some variations in their lounge where a solid double chimney wall was blocking any direct sound. The readings here were significantly lower.They were at their highest where there was a bathroom with a skylight with hard surfaces...a real resonant chamber.It was at its highest here and in the 2 bedrooms. The beds were wrought iron frames and I placed the Mk41 against them to see if they were resonating,but no they weren't.

This sound has been keeping them awake since June....They have been to the local council that controls the permits and zoning but they can't do anything...the factory is correctly zoned and is about to come up for its resource consent to be renewed soon. Other neighbors with wooden houses notice the problem too,but the neighbors on either side of them are in solid concrete and brick houses that do not exhibit this problem as far as they can tell.

I think....

1. The factory is generating ELF from its new equipment that is activating the smoke stack and acting as a transmitter (not RF ).

2. This ELF resonates the older wooden houses but leaves the concrete and brick untouched as far as I know at this stage.

3. The ELF may travel underground by means of the aquifer but primarily through the air where the wave has a chance to develop over the longer distance from the factory, hence not so noticeable close to it.

The tides may affect the aquifer and thus the underground path.

So there's a great deal of work to do yet to so solve this.

The first thing will be to hire a spectrum analyzer and determine some real readings rather than just comparative ones. Then there will be measurements in other houses and at different points around the neighborhood to establish whether its the factory or some other place generating the ELF.

This could all take some time....I have been offered payment...we'll see how big this gets first....

So any thoughts on this would be good from you.

And...do you have any problems the same in your area or house...ELF can cause serious long term damage to your health and those of your family.

Thanks for reading this...its a world away from what I do in the film and TV business...but strangely akin in some ways. It may be that I pass it on to sound environmental scientists to look into.

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Is the noise bothersome in other situations that trying to sleep (ie head down on the bed)--like sitting in a chair?  Is the problem mostly being transmitted thru the bed?  How about isolation blocks (rubber pucks) of the sort used in floating recording studio floors and placing under noisy equipment--decouple the bed from the floor?  If the whole room is resonating they might have to consider doing something to damp the walls--for instance coupling a wall or two to another or to the foundation in a way that changes its resonant frequency.  Are they sure that the issue isn't with their own heating system or plumbing?  A neighbor's water pump or pool cleaning system? Take measurements by all means, but you probably know that your measurements would be easily disposed of by the opposing lawyers in court or in a hearing--you'd have to bring in a paid expert.  It seems to me that the factory is an unlikely source of the problem, unless it is a cover for someone drilling towards the center of the earth...  Is the sound in question more felt than heard?

Philip Perkins

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The Sherlock Holmes of the audio world. I love it.

Is there any time that the smokestack or suspect equipment is not in operation (like Thanksgiving or Christmas?). I'm thinking you might get readings then to use as a reference/control for later.

Doing this in the most scientifically acceptable way will help when you eventually go to the zoning board with your data. At that point, if they reject it, I'm thinking you might volunteer to sit outside each of their houses with a speaker and the recording of what your clients have to put up with.

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Thanks Phillip and Jason...yes I have suggested that they put a high density foam..like Spenco under the beds legs to isolate the bed from the floor.The other thing that I have tried at home but not there yet is a large wok filled with water and placed on a 4 point wok stand on the floor to see if the noise is structure born.If there's any movement it will show up at the edge of the wok particularly if there's a reflection on the water to highlight it.

The other thing that they may have to do is build a bass trap in the ceiling...there's no space under the house.

I have checked there heating and they have no pumps or swimming pools in the neighborhood...its summer here so no heat pumps or boilers going.

Whatever is making this ELF is big....the energy is there....

Yes I'm aware that the comparative readings I made won't amount to anything in court...but some spectrum analysis by environmental acoustic scientists will.

The sound is heard by the two people in their house,but they have talked to neighbors and those closer to the factory where it is very strong.....they are beside themselves as they can't sleep either and it will affect their property values.

They are wondering if a new all night shift has been put on since June as well....its at its strongest at night understandably as the daytime traffic and activities subside.

The factory will close at Christmas I suspect, so it might be a good time to check again then.

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At that point, if they reject it, I'm thinking you might volunteer to sit outside each of their houses with a speaker and the recording of what your clients have to put up with.

If the reproduction of ELF noise become necessary, I would recommend the Eminent Technology Model 17, available here: www.rotarywoofer.com/

Flat frequency response significantly below 1 Hz. That wasn't a typo.

But seriously...

One thought is that Schoeps only measured the frequency response of the Mk41 down to 50 Hz, according to their tech specs. Some Earthworks omni mics (like the QTC50) are flat to 10 Hz, and can record to 3 Hz or so. I don't know if the noise is that low, or if that matters. The wok idea seems cool. I haven't seen that before.

It wouldn't surprise me if the bedrooms act as resonance chambers. If my acoustics knowledge is still correct, a 50 Hz tone should resonate in about typical bedroom (20 ft long), (speed of sound @ 1130 ft/sec). The bathroom might therefore be a partial.

Let us know what you find. This is an interesting situation. Houses should not be musical instruments.

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I have any earlier Schoeps Mk41 and CMC 5U and I also put up the Schoeps CMIT as well so as to get a comparison and its much newer..no bass cut anywhere in my system.....the low end is there.....like very low...I do recall the reason for the Cut 1 being explained that the MK41 could go down to 20hz but the Cut 1 eliminated the sub sonics...I have not measured the bass response,but as I say its only comparative measurements.

The rotary woofer sounds interesting...I read an article back in 1960....when I was 15....the French Army had developed a high energy horn with compressed air that resonated at 7 hz and put out 300 acoustic watts....

apparently it killed everything in a 5km radius...I wondered at the time how they managed to turn it off....

it never became a weapon...

The bedrooms back onto three other rooms that are small but reverberant, so collectively there may be some thing to look at as well...

But it is not just their house...its a general phenomena in the area..some houses are worse than others...

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I worked on a story for NBC News many years ago about Noise Pollution.  We visited an organization that helps people with noise problems.  They're located in Montpelier Vermont and they work with people through out the US.  I think they could be very helpful.  Here is their web address  http://www.nonoise.org/

Andy

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Read a little of David's post

Explanations

In the case of Kokomo, Indiana, a city with heavy industries, the source of the hum was thought to have been traced to two sources. The first was a pair of fans in a cooling tower at the local DaimlerChrysler casting plant emitting a 36 Hz tone. The second was an air compressor intake at the Haynes International plant emitting a 10 Hz tone

Mike

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Facinating, you guys.  I did the Unsolved Mysteries interview of the lady in Taos ( http://en.wikipedia.org/wiki/The_Hum) and and was amazed at how much her life had be invaded by "The Hum"  She tried to  say that possibly the ELF communication of the US Navy with their submaries was at fault, but no serious connection was ever found.  She had to leave town for a time. Couldn't sleep etc.

Jim Mansen

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This sound has been keeping them awake since June....They have been to the local council that controls the permits and zoning but they can't do anything...

Wow, this is a weird problem -- kind of like "Subsonic Activity." This could be a great movie: a family terrorized by strange low-frequency sounds in the middle of the night, and a sound expert comes in to try to capture the phenomena.

Has the couple tried ear plugs? When I'm forced to sleep in a noisy place, I've used the Mack's "Pillow Soft" silicon earplugs and they've worked great. When I was stuck in Italy in 2004 working on HBO's Rome, I had to resort to double earplugs when the building crew in back of my hotel started using jack-hammers to tear down another building. Amazingly, it worked -- dropped the noise down at least 40dB, to the point where it was manageable.

Other neighbors with wooden houses notice the problem too,but the neighbors on either side of them are in solid concrete and brick houses that do not exhibit this problem as far as they can tell.

That's a major clue. I bet a mike planted in the dirt outside would pick up some kind of vibration.

Does the LF hum emanate just at certain times of the day? If they could keep a written record, this could be correlated to the factory down the street. I bet they turn a certain piece of equipment on and off on a schedule, and that might correspond to the LF hum.

Definitely a perplexing problem.

--Marc W.

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'Extremely Low Frequency' takes us lower than 1Hz...

sound can actually be measured in fractions of a Hz aka Cycles per Second ...

it could be cycles per minute, cycles per hour, etc. and still be sound. (not even Earthworks goes there!)

another factor could be the conduction of the sound through elastic media, including conduction paths through the earth (ground), structure, and when the person lies in bed, even bone conduction hearing could be involved...

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Interesting problem, I'd love to know what the source turns out to be!

For any measurements I would think omni capsules would be the way to go to try and accurately reperesent any LF activity. The LF rolloff on any directional capsule is considerable whether cardiod or hyper cardioid. A true pressure condensor element like the Schoeps MK2 would be a more accurate tool, but then the CMC bodies apply rolloff of their own.

Jon Chiles

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Been away for the weekend...and excited to see so many interested in this ELF situation....yes they have earplugs in at night...but that only takes out the higher frequencies not the subsonic ones...when they put their heads on the pillows its at its worst......they told me that they hear it most at night after 11pm but that may just be the daily activities subsiding...they can feel it and are aware of it all the time...I was in their house for about 2 hours during the day and my take on it was that it was subsonic but with higher harmonics coming through with resonating rooms adjacent to their bedrooms.

The small bathroom next to one of the bedrooms was a hard surfaced room with a newish rectangular skylight with 4 panes of glass slanted obliquely towards the factory......a perfect pickup....

I said they should try and raise the bedframes off the floor as a starter by putting some high density foam,Spenco (its used in the sports industry as a high impact protecting foam under sportswear) under the 4 legs of each bed...they sleep in separate rooms....

The other thing I suggested was, when it is at its worst, open the doors to all the rooms that face out onto the courtyard. This will then make these rooms less resonant...my guess. There are 3 rooms like this all between their bedrooms and the factory. So there could very well be rooms resonating,all with slightly different frequencies as they are all different in size.  The term Sympathetic Resonance seems to fit here.

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Ah, I think you've hit on something: the house has a resonant frequency very close to that of the interference in the area, so it's a perfect match. I've momentarily felt before that in cars, where there's a "magic" frequency at which the whole thing feels almost overpowering (below 100Hz). I agree, the earplugs don't do as much below 100Hz, but they did at least help me sleep -- those plus Ambien!

An old friend of mine used to live up in the Hollywood Hills, and he had noisy neighbors who tended to party late. His solution was to acoustically isolate his bedroom and actually use double-walls and decouple the floor, to the point where it was as quiet as a tomb on the inside. It cost a fortune at the time (I think over $10,000), but it definitely worked.

Sounds to me like B&K measurement microphones would be able to pick this up, since they're rated down to 4Hz (referenced to what, I dunno). I think Audio Rents in Hollywood was a dealer -- (323) 874-1000 -- or at least would probably know where to rent them.

--Marc W.

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'Extremely Low Frequency' takes us lower than 1Hz...

sound can actually be measured in fractions of a Hz aka Cycles per Second ...

it could be cycles per minute, cycles per hour, etc. and still be sound. (not even Earthworks goes there!)

  Senator this is SO COOL - stuff like the sound of the earth moving, trees growing and the sound of photosynthesis, pressure shifting probably has a sound under 1 cycle/sec!  These must be sounds we're supposed to feel not hear, just to know we're on planet Earth.  I guess that's why the astronaut went crazy in that Twilight Zone where he dreamed he was in a whole town that was vacated seconds before his arrival.

  Sorry to hijack but I just had to interject.

  I would go NUTS very quickly if I had any type of hum man, I freak out in "modern luxury apartments"

in NYC that have air circulating all the time in the kitchens - I wouldn't last a week!  I've almost unplugged my fridge because it can get loud at night.

  This is fascinating and I feel real bad for the folks with the resonating wooden houses.  Please keep up updated with this!

  One thing that might help mitigate the hum would be for the people to play a white noise machine at night?  You know those things that play the forest or ocean.  Maybe having the extra sound would turn down their ears so the hum is softer like the daytime?

  It's funny I recently read a comic about a hotel that boasted dead silent soundproofed rooms - it went out of business right away because people were freaking out at the silence.  I think I too need some kind of reference that the rest of the world is there outside my window...

  Dan Izen

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Dan, like your example of the hotel, it's exactly that - noise - that people living in cities are accustomed to. if you lived in a very quiet place for a very long time, i guess something like the low freq hum would drive you nuts. i guess it is not really a solution for these people to add some noise (albeit in the form of controlled white noise) to their lives! :)

-vin

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I've even mentioned the anti-noise solution,which we are all familiar with the principles.

Here's something from Tomlinson Holman.

http://www.good.is/post/inventions-anti-noise/

This would be difficult to incorporate in their house as there's not just one wall but a series of windows across the back of the house. But there are other anti-noise type setups which could offer a solution although I'd prefer to deal to the original problem as there are many houses involved. As I said in originally,this all started in June of this year. The factory has been there for many years and not caused the low frequency,just general broadband noise typical of many factories.

I do have a secret weapon up my sleeve ( always have another way of tackling your problems).... I have a lifelong friend who is a Technical Director for the City Council that governs the operating parameters for all the factories in our area......so we'll see what happens when that avenue is activated.....if you get my drift....it's complicated......

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Last night I went to our monthly local Audio Association meeting ( the Christmas Party). This is a group formed from all the people who work in any form of the sound business from Film and TV mixers,Live sound mixers,radio,hire people,the odd DJ...lol..and some who work in the scientific side of sound and development of products for commercial and scientific use. A great bunch of people who are all willing to share their many years of experience.

So I asked a scientist and an analytical troubleshooter who gets called all over the country to solve problems like we have here. They said "hmmmmmm thats difficult,especially when you are dealing with trying to measure and quantify subsonic sound."

We discussed several scenarios that I could go down......all of them look difficult.

The woman whose house it is, is doing door to door polling at the wooden houses in the area to establish the extent and nature of the problem as the residents hear or feel it.

One of my colleagues has offered a vibration measuring device that he uses for very low frequency problems....it'll go down to 1hz....but the problem is as he sees it..trying to get a measurement not affected by me holding it or mounting it so it doesn't pick up other extraneous low frequencies that are part and parcel of everyday life. The other thing is to try and define where it is coming from precisely,and that ain't easy. He also suggested that a large solid flat surface would be needed to propagate the amount of energy required to affect the houses in the manner we are seeing in this small sample. So I drove behind the factory we suspect on the way home from the meeting. There,adjacent to the factory is a tall,solid concrete block wall running for maybe 75 yards....the propagating flat surface?????

It all felt a bit surreal late at night in this out of the way side road...lol.....but I could hear the low frequencies emanating from their plant.....and could imagine the wave developing out into the local community.

He suggested calling in the experts..an acoustics firm that is very experienced in these matters....they have all the right equipment and knowledge to gather the data.

He also suggested approaching it from a different angle...getting an attorney involved before too much longer and proceed with it as a Tort of Nuisance....

To be continued.......

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