# Help me solve a mystery **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [May 31, 2014, 10:03pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723 "2014-05-31T22:03:40Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Typo\_Negative](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/typo_negative/32/484_2.png) [@Typo\_Negative](https://boards.straightdope.com/u/Typo_Negative)\ **Post date:** [May 31, 2014, 10:03pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/1 "2014-05-31T22:03:40Z")
Or, more to the point, solve one for me. We will call this the Mystery of the Ghost Knocking at the Door. We moved to our present home last October. It is a two story house with 2 bedrooms and a bathroom upstairs. These are all on one side of the house. On the other side a very high ceiling, maybe 25 feet at the highest point. It highest in the center and slopes down on either side. There is a staircase. At the top, you can see living room, dining room and family room on the 1st story. Now the mystery. We keep hearing what sounds like someone knocking at the door. We keep going to the door and open it to …no one. The knocking started almost as soon as we moved in. The owner denies all knowledge of it. It started like a steady knock, maybe 4 or 5…normal for someone who knocked at the door. The knocks seemed a little slow, but not much. This would happen once every week to every other week. The knocking has now become more frequent and the knocks are faster, like someone knocking at the door in a big rush. The number of knocks has also increased, 10 to 15 at a time. Today, this has happened six times already but today is anomaly. As we have investigated, such as we can, we seem to notice that sound comes not from the front door, but above the kitchen, like a wooden shutter banging in the wind, except for the speed…and the fact that there are no shutters. There are no rooms above the kitchen. It is at the back end of the house. There is an empty crawl space above, accessible from the top of the stairs. It is empty space. There are no ac\heating ducts. At most, a vent from the stove. The empty space is the size of a small bedroom with a sloped ceiling. There is nothing that we know of that could account for the knocking. My girlfriend’s sister watches the ‘ghost adventurer’ and ‘haunted this-or-that’ constantly, so we tease her by saying it’s ghost. I started out sure it wasn’t. Now… What could it be? ---
**Author:** ![FairyChatMom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fairychatmom/32/22080_2.png) [@FairyChatMom](https://boards.straightdope.com/u/FairyChatMom)\ **Post date:** [May 31, 2014, 10:20pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/2 "2014-05-31T22:20:00Z")
A squirrel in the ceiling? I dunno, I got nothing. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [May 31, 2014, 10:33pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/3 "2014-05-31T22:33:02Z")
Has the knocking changed to coincide with the seasonal temperatures? House might be warming and cooling causing the knocking sound. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [May 31, 2014, 10:37pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/4 "2014-05-31T22:37:22Z")
Air in the plumbing? Sorry, I guess it’s more accurately lack of air in the plumbing. I don’t know nothin’ bout plumbing, obviously, except that sometimes, it knocks. [Yahoo | Mail, Weather, Search, Politics, News, Finance, Sports & Videos](http://voices.yahoo.com/how-fix-knocking-water-pipes-659729.html) > [@](#): > > Knocking water pipes seem to be a mystery to many homeowners. One day the knocking sound may occur, but each day the knocking will get louder. Although there is nothing seriously wrong with your pipes, the knocking sound is an unnecessary irritant. The fix for knocking water pipes is so easy that you’ll want to try it right away. It doesn’t require a plumber or any new parts, and you should be able to fix it in less than 20 minutes. > Knocking pipes occur because the water supply pipes in your home are under pressure. This is required so your plumbing system can function. In addition to the pipes that carry the water, there are air chambers built into the pipes that cushion the pressure when you turn on the faucet. > > The knocking occurs when the air in the pipes naturally depletes. When you turn on the faucet without the normal amount of air in the pockets, the water slams into the air or the end of the pipe, producing the dreaded knocking sound. ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [May 31, 2014, 10:43pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/5 "2014-05-31T22:43:57Z")
Tree branch? twigs, acorns, or other things falling out of a tree and hitting the roof or the side of the house? I lived in a house in a wooded area, and we got acorn falling off an oak all the time, not just in season. There’d be a gust of wind, and several would fall. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [May 31, 2014, 10:45pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/6 "2014-05-31T22:45:09Z")
squirrel ghost in the empty crawl space. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [May 31, 2014, 10:55pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/7 "2014-05-31T22:55:09Z")
Satan. ---
**Author:** ![not\_what\_you\_d\_expect](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/not_what_you_d_expect/32/3246_2.png) [@not\_what\_you\_d\_expect](https://boards.straightdope.com/u/not_what_you_d_expect)\ **Post date:** [May 31, 2014, 10:59pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/8 "2014-05-31T22:59:23Z")
Maybe a bird? We used to have one that knocked like that outside our bedroom. ---
**Author:** ![Typo\_Negative](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/typo_negative/32/484_2.png) [@Typo\_Negative](https://boards.straightdope.com/u/Typo_Negative)\ **Post date:** [May 31, 2014, 11:13pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/9 "2014-05-31T23:13:46Z")
> [@HoneyBadgerDC](#): > > Has the knocking changed to coincide with the seasonal temperatures? House might be warming and cooling causing the knocking sound. It does seem to have sped up as it got warmer. Although today is a moderate day. There are tree limbs in the area. No flora or fauna. ---
**Author:** ![Missy2U](https://avatars.discourse-cdn.com/v4/letter/m/3bc359/32.png) [@Missy2U](https://boards.straightdope.com/u/Missy2U)\ **Post date:** [May 31, 2014, 11:14pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/10 "2014-05-31T23:14:29Z")
Not real sure, but if it responds to the name “Jodie”, I’d be worried. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [May 31, 2014, 11:46pm UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/11 "2014-05-31T23:46:11Z")
We had a knocking/ticking sound coming from one of the fan vents in our bathroom when we moved in. Something about the wind blowing would turn the fan blades or something and make a knocking sound. I wonder if something similar is coming from your stove vent hood. ---
**Author:** ![PurpleClogs](https://avatars.discourse-cdn.com/v4/letter/p/f04885/32.png) [@PurpleClogs](https://boards.straightdope.com/u/PurpleClogs)\ **Post date:** [June 1, 2014, 12:01am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/12 "2014-06-01T00:01:47Z")
Do you have a whirligig (I don’t know what it’s real name is) on top of your roof? Squirrel running across the roof? Tree branch barely touching the house? Window pane rattling? Shutter loose? Pesky neighbor kid? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [June 1, 2014, 12:12am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/13 "2014-06-01T00:12:24Z")
Are you sure no one is knocking and running away? Just for kicks try leaving your front door open for a few weeks whenever you’re home and see if it stops. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [June 1, 2014, 12:16am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/14 "2014-06-01T00:16:53Z")
> [@USCDiver](#): > > We had a knocking/ticking sound coming from one of the fan vents in our bathroom when we moved in. Something about the wind blowing would turn the fan blades or something and make a knocking sound. I wonder if something similar is coming from your stove vent hood. In your bathroom fan there’s a check valve to keep outside air from coming in. When it’s windy out and air moves across the exhaust port and make the valve bounce. It’s just a light weight plastic flipper. You can see it in the open position in [this picture](http://optea-referencement.com/wp-content/uploads/2014/02/Broan-White-Bath-Fan-Design.jpg). ---
**Author:** ![toofs](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@toofs](https://boards.straightdope.com/u/toofs)\ **Post date:** [June 1, 2014, 12:21am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/15 "2014-06-01T00:21:44Z")
Quoth the Raven “Nevermore.” ---
**Author:** ![kayT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayt/32/3633_2.png) [@kayT](https://boards.straightdope.com/u/kayT)\ **Post date:** [June 1, 2014, 1:13am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/16 "2014-06-01T01:13:17Z")
Could it be your refrigerator? Ours makes some amazing rapping sounds and the owner’s manual says it’s normal that it does this. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [June 1, 2014, 1:30am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/17 "2014-06-01T01:30:57Z")
> [@Joey\_P](#): > > In your bathroom fan there’s a check valve to keep outside air from coming in. When it’s windy out and air moves across the exhaust port and make the valve bounce. It’s just a light weight plastic flipper. You can see it in the open position in [this picture](http://optea-referencement.com/wp-content/uploads/2014/02/Broan-White-Bath-Fan-Design.jpg). Yes. That’s the thing. ---
**Author:** ![joyfool](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@joyfool](https://boards.straightdope.com/u/joyfool)\ **Post date:** [June 1, 2014, 1:34am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/18 "2014-06-01T01:34:06Z")
> [@kayT](#): > > Could it be your refrigerator? Ours makes some amazing rapping sounds and the owner’s manual says it’s normal that it does this. Old school, like Run DMC, or more modern, a la Jay Z? 😛 ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [June 1, 2014, 1:34am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/19 "2014-06-01T01:34:30Z")
> [@USCDiver](#): > > Yes. That’s the thing. It took me a while to track it down in my house as well. I’m one of those people that has to know how everything works and if I’m sitting in my house and can hear a motor running or a thing making noise I won’t be able to sleep until I figure out where it’s coming from. That one took some thinking. I probably wouldn’t have been able to place it if I hadn’t installed the fan myself. Suddenly, I could picture it flappin’ around as the wind pulled a vacuum on the vent. ---
**Author:** ![Count\_Blucher](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@Count\_Blucher](https://boards.straightdope.com/u/Count_Blucher)\ **Post date:** [June 1, 2014, 3:34am UTC](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723/20 "2014-06-01T03:34:26Z")
Have you tried switching your furnace to “High Octane”…? [Next page](https://boards.straightdope.com/t/help-me-solve-a-mystery/689723.md?page=2)