We moved into our home about 20 months ago. Not long after we started noticing a noise. Until today, my wife and I were apparently the only ones who could hear this noise. That's because it's nearly inaudible unless you stand in one place (the master bath toilet area) when the house is completely silent. The furnace must be off, you have to stand perfectly still, and nobody can make any noise at all.

Under those conditions, you can hear what sounds like a cat crying. It's a sound that rises and falls and then is silent before rising and falling again. It repeats this in a perfect cycle and never stops. As far as we can tell it has made this sound 24/7 since we first noticed it about 18 months ago.

Up until today I had no way of conveying what this sound was like, but a friend of mine has a much nicer recording device and was kind enough to help us try to capture it. He did his best and we've now ended up with this audio file. Unfortunately it's still VERY noisy, and there's a bad hiss. I tried removing it in Audacity, but it made the file very garbled. I hope you can hear it over the hissing. The sound happens three times in that clip, about every four seconds at the 3, 8, and 12 second marks.

Does anyone have an idea of what this might be? Can you hear it?

Can hear it, no idea what it might be.

Do you still hear it after switching off the mains power at the breaker box?

Wow that is creepy. You are right, it sounds like an animal crying faintly in the distance. But if it were, it wouldn't go on for 18 months without changing. If you had animals living under your floorboards you would at least hear seasonal cycles. Although when I was a new parent, I thought that our baby would never stop crying, at least she didn't cry for 18 months straight. Wow.

So it must be mechanical, plumbing or electrical.

It can't be anything battery powered... unless... do you have a battery powered clock in that bathroom? I know I've had clocks which made faint unusual sounds sometimes.

Failing that, it has to be either something on the mains power, or it's something that just has a natural cycle, like some kind of thermal cycling. I would have suspected something related to the air flow in the house due to the furnace, but you said it happened with the furnace off. It can't be the house creaking, that wouldn't happen 24/7/365, it would go in cycles with the temperature, the wind, and the seasons.

As Mark said, cut the main power to the house and see if it still occurs, to narrow down whether it's caused by something that's plugged-in. Also listen more closely, move around the room, listen to hear if it's coming out of a drain pipe or an air vent, try to narrow it down further.

Is there some appliance, such as a water heater, in or near that bathroom? Could be the pressure release valve on the water heater, venting pressure and then letting it build again, at regular intervals. Or any other place where there might be that kind of pressure/build/release cycle. I know that some houses have a pressure regulator valve for the water at the point where the water pipe enters the house, maybe it's that.

If you're on natural gas supplied by the city, perhaps it's related to the pressure regulator for the gas, maybe that's just outside your bathroom. Also look and see if the electric or gas meters are on an outside wall near that bathroom, maybe one of them is making the noise.

Really interesting problem.

Ahh.. I suppose it could also be a "hidden vent" (under counter) valve for the plumbing, perhaps.

I don't know much about plumbing, but I'm wondering what kinds of vents that a plumbing system might have. The only kinds I can think of are the ones that vent pressure from water heaters, and the vent tubes from the sewer pipes that stick out the top of the roof. The latter is just a tube as far as I know, there is no valve associated with it that might make a whining sound.

But yeah, it sure sounds like some kind of pressure release/build cycle through some kind of...

OH HEY. You said it was in the master bath. Is the sound coming from the toilet flush mechanism in the toilet tank? I have, on more than one occasion in the past, had to replace toilet flush mechanisms because they would make intermittent noises.

Although yours seems to be occurring in much faster cycles than I've ever heard before, I could see how it might happen this way. Here's how the cycle worked in the ones I had to replace:

- Flapper drain seal is not particularly good. Old flapper or some such. Or perhaps the chain that attaches to the flapper is loose enough to have folded and lodged partly under the flapper, causing a continuous leak.
- Tiny amount of water leaks past the flapper slowly.
- Water level lowers slightly over time.
- Floater sinks slightly and barely engages the flush valve. Not enough for a full flush, but just enough for a tiny amount of water to come out (here's where the noise is).
- Water level rises a bit and lifts the floater, closing the valve.

A combination of old flapper which leaks water, and an old flush mechanism with old seals on the valve that allow small amounts of water to leak out without fully flushing, can cause this.

I've also had the floater in one system be made of styrofoam, which got old and no longer stayed dry, it started to waterlog, which made the mechanism be "twitchy" where it sort of was on the edge of flushing constantly, thus making nearly continuous noises.

Yeah, could be the toilet valve. Almost certainly!

To test:

1. flush the toilet.
2. turn off the water valve for the toilet before it refills the tank.
3. listen for the sound.

Feel free to reverse steps 1,2 if you don't mind a bit of sewer gas or extra vent noise.

Thanks guys! I do need to try turning off the mains and see if it still happens. If it does, that'll really creep me out.

Here's some responses in no general order:

I don't think it's the toilet valve, but I'll check. The sound seems far more removed than that.

The water heater is two floors down from the bathroom, and the gas meter is pretty far away as well. I've also never heard this noise when standing right next to either of those things.

I suppose it could be plumbing or vent related, but the perfection of the repetition really makes me feel like it's electrical. I guess I'll have to wait to test that thought until the mains test.

The only place where this noise is audible is in the separate toilet room inside the master bath. One side of this closet-sized room is the shower, which has a complex valve in the wall that could be the source (but I know exactly where it is and I don't hear the sound louder where it is). Another side is a guest bedroom where my office is, but there's no sound in there. The third side is trickier because it's an attic-like area over the garage, which is actually somewhat separate from the rest of the attic. This makes me think it could be an attic fan, which would make sense because it could be something spinning up and down repeatedly.

I'll cut the mains and let you know what happens!

Yes, if you have automatic electric-powered attic fans, that could be the source of your noise too.

The fact that you only hear it in the toilet room makes me think it's the toilet, though. That kind of "moaning" sound makes me think plumbing more than it makes me think electrical.

Well, it's not the innards of the toilet. I drained it and turned off the water and I could still hear it. It was also coming from nowhere near the toilet.

It's odd, though, I'm completely unable to hear which direction it's coming from. I would at least think that I could hear whether it's coming from a direction on one side of the toilet area or the other, but I have no idea at all!

Then it's likely coming from above or below you.

Does that bathroom have a window? Does the noise change depending on whether the window is open or closed?

Oh hey. Here's a question. Does your house use a booster pump? You mentioned it was a multi-story dwelling.

http://inspectapedia.com/water/Booster_Pumps.htm

Maybe that's what's making the noise, and the pump or its pressure-detection circuit is faulty.

Also, I don't know whether you're on a city sewer system or on a septic system. If you're on a septic system, those have pumps too, which can make noises like that. Although I don't know why you'd hear a septic pump only from an upper floor bathroom, unless the vibration was transmitted through the piping.

Cool ideas, but we're on a city sewer and I'm almost certain that we don't have a booster pump. I know that would have come up. A little after when we moved in we had water damage and had to gut the master bath. I'm 99% certain that all we have is the main water heater (which we also had to replace this winter - don't get me started on the things we've had go wrong with this house).

The toilet area does not have a window, but the bathroom does. However, by the time I get anywhere near the window I can't hear the noise anymore. I really can't hear it very well at all if I'm outside that toilet closet. Even when I'm in there it sounds like it's very far away.

I should mention that I've been up in the attic, and I've had workers up in the attic, and none of us have ever heard anything up there.

*edit*
And the only thing that's below the toilet is the garage. I can't hear anything in there either. That's one of the things that makes this so weird: the way this noise sounds in that toilet closet, you would think that it would get louder if you moved in some direction. I can get to almost every single side of that room except the area over the garage and part of the attic. I'll have to figure out how to get in those areas (the garage one is particularly difficult).

I'll try turning the power off first...

Try blocking off the various sink holes / drains one at a time or all to begin with. Plugs in where possible but given it's such a quiet noise, shouldn't take much to muffle it if that's where it's coming from.

All the drains should have water traps on them but perhaps it's coming through on the pipe itself?

Well, we can cross plumbing off the list.

I just shut off the power and the sound went away. I guess we haven't had enough power outages at our place to have noticed whether the sound was gone when the power was out.

Now we just need to figure out which powered device is making that sound...

Switch off circuit breakers one by one would narrow it down to a particular circuit (e.g. lights vs power outlets)

In my house, each breaker is geographic. The lights and the power outlets for a given section of the house are on the same breaker. So narrowing it down to one breaker might not help that particular thing.

But... narrowing it down to one breaker might certainly be of help. For instance the garage or attic might be on a different breaker than the bathroom. So if you kill the garage breaker and the noise stops, then there might be a chance you're hearing something from the garage filtering through.

Here's another question for Dignan:

You mentioned somewhere earlier that the section of the bathroom with the noise did not have a window. You had to leave that section to get to a window. Well, I'm pretty sure that WCs which don't have windows are required to have ventilation fans. Have you already narrowed down that it's not the vent fan for that room?

Most vent fans are activated by a switch. Where is the switch for the vent fan for that room? If you don't know, then, maybe there's a switch somewhere that's always been on and the noise will go away if you turn off the switch.

The noise certainly could be a vent fan turning on and off at regular intervals due to being old and flaky. I've seen fans that have gone bad which, even when turned on all the time, will spin up and spin down like that. If the fan blades were rubbing against something, they would make a rising and falling pitch, much like that sound.

Another suggestion: Does your house happen to be situated next to a dog park?

Heh, I wasn't aware of Night Vale. Very interesting!

There is a vent fan in that room, but I know where the switch is and the fan is brand new. It's possible that the sound could be coming from it, but I'd be surprised...

I could try turning the breakers on and off, but I don't think that would tell me all that much about where it is. I already know that it has to be somewhat near that WC, but I don't know which direction. Like Tony's place, the breakers are mostly geographic and are extremely poorly labeled. I'm always shocked by how poorly most breaker boxes are labeled in this country. Most of mine just say something like "lghts & plgs," with no indication of WHERE those lights and plugs are located. I've also noticed from past experience of replacing wall switches that there is rarely a logic to which switches are on which breaker. For example, there are three breakers that cover all the light switches in our kitchen.

I think the next thing I'll try is to find a way into that space above the garage. I'm a little worried about what I might find up there. It's extremely difficult to get to, so I don't know if I want to risk my health to get up there, but we'll see. Thanks for your help so far, guys.

I just love a good mystery.

Me too! This has been a good one because a lot of people didn't even believe my wife and I that the noise was there. My father in law went in the WC to listen for it, but swore we were imagining things. Then again, he's a general contractor and his ears are probably shot...

Ok. In Australia breakers are always (to my knowledge) broken up into lights vs power points/fixed electrical. Definitely "geographical" after that though of course. Usually light circuits aren't RCD protected so are on separate circuits.

Still might be worth turning all off bar the one you think it is. Might help rule out something elsewhere somehow transferring the sound? If you know which breaker you could at least go around the house and see what's still active.

Edit: Yeah Tony said the same - missed it.

Same here. Power sockets are also on 20A breakers and use 2.5mm² wire, while lights are on 16A breakers and use 1.5mm² wire. Up to 8 power sockets may be implemented on one circuit that's protected with a 20A breaker. If there are more, you need to create an additional circuit.
Also, ALL circuits are RCD protected. There are 2 sorts: 30mA for the "wet" rooms, like bathrooms, kitchens and the room with the washing machine (basically, anywhere where there's water), and 300mA for the "dry" rooms.

Very interesting how the building electrical codes differ in different countries.

So, any word? We're waiting excitedly for the next chapter in this mystery.

Ha! Very sorry, I'm just trying to build the suspense!

Actually, I just let my neighbor borrow my only ladder, so I'm going to need to wait until at least Wednesday before I can go up to check out the area I think it may be coming from.

In reality, that gives me some time to think about whether I actually want to go up there. It's pretty dang high up and I don't think my ladder can get me up that high...

I think you want to.

If it's electrical, and it's making that repeating on/off noise, that means it's probably a pump or a fan or something that's not working right. Electric motors that aren't working right are potential fire hazards.

Of course if it's been making that noise for 18 months without catching fire, then maybe it never will.

Good point! Yeah, it's partially been a worry to me. Given all the things that have gone wrong with this house (so many things!) I do want to figure this one out.

Turning the power off would at least clarify whether the noise is coming from an electrical device or something non-electric.

Powering down the entire house will also make the house very quiet, which might help you hear and possibly better locate the sound.

Dang. I don't think it's coming from that area over the attic. I poked my head through the access panel in the garage, easily 12-14 feet off the ground. I didn't have the guts to lift myself up into the area, but I was able to look around pretty well and there wasn't a single thing in that space that would have electrical power running to it.

The mystery continues! Sometime I'll have to try to get back into the attic space over the bath. It's a very difficult area to get to...

He's already done that (see above).
But has not done a breaker by breaker isolation yet.