Random annoying noise from speaker

[Tnr_1]

I have "Logitech Z-313" (2+1 speaker) and and randomly (even when they are not plugged into computer or phone) they make annoying sounds for about 30 seconds. The sound is the same, even when the volume is all the way down.

When I plug it to phone suddenly annoying sound disappers but the result is not the same for computer, ie. plugging to computer does not change anything. It does not matter computer is on or off, annoying noise occurs randomly.

Thanks in advance.

 

[Tnr_1]

So far no electrical equipment fails.
I tried to connect speaker and computer different power plugs and also tried to use surge protector, but nothing is changed.

There are usb sound cards, planing to buy one. But i am not sure it works.

 

[Tnr_1]

Does the sound change if you touch the 3.5mm plug?

Yes, touching she speaker' 3.5mm jack drastically affect sound.

I think speaker has no problem since when i connect it to phone everything is fine.

 

[Tnr_1]

One more observation:

As I said before when speaker plugged into phone random annoying noise disappears but when phone connected to PC via usb cable then random noise again occurs.

Also, I did the same things by connecting speaker to TV. Random noise comes from speaker when plugged to TV, too. When I connect phone to TV while speaker plugged to phone, noise again occurs.

I do not think it is ground loop issue since both TV and speaker have not ground pin (they have just two pins). Thanks in advance.

 

[tuna1983]

Hi again,
When i touch ground/sleeve part of 3,5mm jack while it is not plugged to pc, annoying sound goes away. Since speaker has not ground pin, touching sleeve part of jack may cause ground affect. Any idea to use this to eliminate noise?

 

[jsmithepa]

Post a link to a mp3.

 

[Tnr_1]

Have you tried plugging your 3.5 mm jack into another pc? it may be that your pcs jack is damaged and is not contacting the ground pin

I do not think cause of noise is damaged jack. I used the same speaker and PC in my old house and there was no such noise problem. Frequency of noise drops during night, I heard less noise especcialy after 11 pm. Therefore I think sourse of noise is related with electricity. Maybe a prasite in electricity or maybe grounding is not enough during day time for thirty-floors building. Any more suggestions? Thanks