Why do I feel vibration in my head when I try to sleep?

Identifying source of/fix for low frequency vibration in apartment

• This one has me stumped so I'm hoping someone can offer some help... During the last couple of weeks I've noticed a low-pitched vibration in my apartment. It isn't audible, but I can feel it, especially when I'm still (such as when I'm studying or trying to go to sleep). It's really annoying and I can't seem to locate the cause of it. A few possibilties: 1. It just turned cold here in Minnesota so people have there heat on for the first time since I've lived in this apartment. Perhaps the vibration is eminating from the heating system. 2. They were doing some inspections on the fire alarm/sprinkler system in the building. It's possible that perhaps the water pressure in the pipes is too high/low and that is causing the vibration. 3. I just had a neighbor move in below me around the same time this all started. I checked with her though and she doesn't seem to be running anything that could be causing this (i.e. an air cleaner). The only things that she was running were a fan and a heat lamp for her son's iguana. I don't see how either of those could cause the vibration. Now on to my "question". 1. I'm looking to try to find out what is causing this. I'd love to see something (perhaps from Usenet) from someone who has experienced a similar problem before. 2. I'm also looking for the solution. If I can nail down the cause then a solution should be easier to achieve. But without a cause there isn't much hope for a solution. 3. I'm also looking for a way to "measure" the vibration. It is very subtle and my guess is that some people wouldn't even be able to feel it. If my apartment manager comes over to check this out I want to be able to have some tangible evidence of my problem. I was thinking a seismometer might pick this up but I have no idea where to get one cheaply or rent one. Any other suggestions? Finally, I don't expect the researcher to have all of the answers to all of my questions. However, I'm listing this with a fairly high price because I'm looking for information that will get me closer to a solution. Please feel free to let me know if there's any additional information that you need. I tried to provide as much as possible without boring anyone to tears with my quirky problem.

• Answer:

  Dear jpbischke - Thank you for the opportunity to help you out with this vibration issue. As a electronic engineer I have dealt a little with minute vibrations of unknown sources. Trying to find them and Isolate them. This is going to have to be a several step and clarification answer as I need some more assistance from you in order to get you the complete answer. Does someone in the building have a rock tumbler and lapidary as a hobby? Does someone have an aquarium with a pump? Does someone have vacuum pump running, sometimes associated with indoor Jacuzzi tubs? Have you turned off you own refrigerator or freezer? What other appliances do you have in your apartment? Is the vibration constant or intermittent? Is the location of the apartment near any mass transit or freeway systems? Are there any evaporative coolers or other heat exchangers on the roof of the apartment building? How old is the apartment building? What floor do you live on? What kind of flooring do you have? Hardwood? Carpet? Vinyl? How is the building heated? Boilers? Gas? Oil? What is relevant is that even on the 2nd or 3rd floor of an apartment building you could feel low frequency vibrations from the subway trains a block away under ground. I know you can also feel the low frequency vibrations from truck traffic on heavily traveled roads. The high frequencies travel through air but not very well through ground and rock. But low frequencies do travel well through the ground. Things like the joints in furnace squirrel cage blowers can cause low frequency vibrations as they rotate over the pulleys. Buildings have a natural resonance and if anything "drives" it the effect is to amplify it. Buildings unfortunately have resonance’s down in the 6 Hz range and road traffic can easily "drive" it. I talked to engineers designing SGS's fab in Phoenix and they had done low frequency vibration studies using seismometers and accelerometers and were then making a conscious effort to prevent the building from having a resonance at the frequencies present on their land next to Bell Road. I believe it should be possible to rent vibration sensing equipment from US Rentals, etc. but it probably isn't cheap. A cup or bowl of water often will show bulls eyes if there are vibrations present. You may also need to add coloring to the water if the vibration are so low as not to be visible in this way. Placing several around the apartment and plugging and unplugging items could isolate your apartment from the rest of the building if the vibrations remained. There is other equipment available for testing vibrations but most are used in University Study programs and are not cost effective for your needs. Depending on the ability to get cooperation, cutting the power to various parts of the building for a minute or so would narrow down the cause but of course getting people to allow it or getting the manager to shut off the circuits one at a time might be difficult. See the above water test first since you want to have proof that there really is a vibration in the building. I would also concentrate on your new neighbors somemore to see if they are willing to help you find the source of the vibrations. You can do the water test in their apartment as well. Try having her turn things off as well as you test her apartment if she will let you. You need to isolate as much as possible. Where the vibration is and is not. Is the vibration on the ground floor? Does it get worse as you go up levels. Think of this as a science project. Are there any architectural features of the building, which might be vibrating in the wind? It could be something as silly as a gargoyle. Unfortunately, you may be unable to isolate the vibration even if you find it in the end. So you may want to start considering how to isolate your bed so that you do not feel the vibrations when you try to sleep. I appreciate your question and look forward to working through this with you. Morningstar