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.
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?
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