What is causing strange sounds from glasses in my apartment at night?

[mcgyver123]

In our apartment, for the last few months, my wife and I are being puzzled by strange sounds coming from the dining area while we remain in the bedroom at night. The first time we heard, I was quiet. Then my wife said, "Did you hear that?" So, it was no hallucination whatsoever. It is a distinct sound of a spoon stroking a glass. Sometimes once, sometimes twice.

These are the confirmed facts about the surroundings:

1. At night, after dinner, we leave our glasses on the dinner table.
2. The glasses are kept far enough from one another. So, no earthquake in the world can bring them together for mutual bombardment or anything like that.
3. There are no spoons on the table.
4. Our mobiles/tabs do not have any settings for notifications, emails, messages, that would sound like that.
5. We reproduced those sounds by one of us hitting a glass with a spoon on the table and another staying in the bedroom in order to sense any difference. There was no difference. The sounds definitely originated from the dinner table and, more precisely, from those glasses.
7. Other possible sources are compressors of the fridge, air cooler, etc, but they do not sound like that.
6. We do not drink. So, we do not get drunk. We do not take any powerful medication. We have no history of hallucination.
7. Those sounds are so sharp and distinct that they just cannot be coming from neighboring apartments in the building.

So, would any physics enthusiast attempt to explain what is the physics behind those sounds being produced from glasses kept apart from one another on the table?

 

[Simon Bridge]

Welcome to PF;
Not enough information. (I used to investigate these sorts of things.)
It's reproducable though - so you may be able to investigate: set up a camera.

You are getting a "ring" as if a glass is being struck "pinggg"?
It is strongly tempting to think that this means that someone or something is striking a glass - but let's resist that for now. There are lots of reasons you may get a ring like that. You will be aware that cooling metal often makes pinging noises exactly as if struck by small ball-bearings but that is not happening. I'm not saying the glasses are just cooling down, I hope to illustrate that what something sounds like may not tell you much about what is happening. We need more information before proposing possible causes to investigate.

You are consistently getting no more than two? How many glasses are left out on the table?
(Vary the number and see what happens. Put all the glasses away and see if you still get a noise.)

Have you always left glasses out and the ring noise has just started up recently?

What sort of glasses are they? How, precisely are they placed? (Photograph the typical setup.)
What sort of surface are the glasses sitting on?
Does the noise stop if you put a tea towel over each glass individually?
Does it stop if you change the surface the glasses are sitting on?
Does it have to be the table? ie what happens if you put the glasses on a sideboard or on the seat of a chair?

What happens to the temperature in the room?
Are the glasses warm when placed on the table: ie. maybe fresh from being washed?
(If the cause is related to the environment, it may stop before being isolated.)

 

[davenn]

do you have smoke alarms in your house ?

I remember being driven nutz for several months some years ago by a smoke detector that was in storage but had battery in it
and at nite when all was quite, we would hear this regular high pitched squeak.
was the detector alerting that the battery was getting flat and needed replacing

if you have detectors, it wouldn't surprise me if it was the same thing
if you don't have detectors, then I would do as Simon suggested and set up a camera ... that's not difficult to doDave

 

[sophiecentaur]

Try taking out the alarm battery or putting a new one in. The experimental approach could be the way forward before you have the place exorcised. [emoji846]

 

[A.T.]

7. Other possible sources are compressors of the fridge, air cooler, etc, but they do not sound like that.

They sometimes create vibrations, which cause other stuff to make noise.

 

[litup]

It certainly has nothing to do with your glasses and most likely due to some form of electronics, like the smoke detector mentioned. It would help if you were in the room when it made the noise but if you have a smoke detector in the kitchen, you could just put it in your bedroom and maybe the thing will make that noise in the middle of the night.

 

[NascentOxygen]

Metal bars can ring like a glass tumbler. Your focussing on the glasses when there is nothing that can strike them might lead you to overlook the real culprit.

 

[mfb]

Sometimes once, sometimes twice.

Does zero also happen?

I would not expect the glasses to be the origin, but that is easy to check by putting them away or wrapping them in a towel, as suggested already. Further investigation then depends on the result of that check.

 

[fresh_42]

There also might be vibrations from nearby trucks, trains or aircrafts ... or pets, eventually mice.

 

[mcgyver123]

Thank you everyone for your precious replies. Each reply is thought provoking.

Simon, I tested with one glass, and then two glasses. Here is some more information, as you said the provided information is not enough.

There is a heating+cooling system in the living room. The system is, sort of, part of the wall. Old-fashioned but effective. We just change the mode of it depending on the season. Its mouth, through which warm/cold air comes into the room is pointed toward the dining room, from all the way across the living room.

It all started toward the end of winter when one night there was a glass on the table. I do not remember leaving glasses on the table before that. My wife and I heard a "ping" sound, as you termed. But it was not a pingggggggggg sound. It was sharp and short, like "ping". Then we tested with two glasses and the result was "ping ping". One ping after another in quick succession. Sharp and short. We even tested by putting the glasses upside down. The same results were attained. Recently, 2 weeks ago, we changed the mode of the system from heating to cooling.

And, yes, I tested by putting away those glasses and no sounds were heard. Even when I put glasses on the table, I do not hear the sounds every night. Or, should I say, I do not get awakened by sounds every night?

I wish I had pictures of the living room, dining room with glasses on the table. I will do it soon.

 

[mcgyver123]

Another thing is that, there is a smoke detector on the wall. But, recently, there was a fire incident in the building and all apartment units had the detectors making sounds, forcing almost everyone to go out. In our apartment, there seemed multiple sources of sounds! So, I am unsure if I have one or multiple smoke detectors!