ELI5: what causes the weird buzzing noises when you touch a 3.5mm jack plugged into a speaker?
Your body is acting like a radio antenna, and conducting that signal into the input of the amplifier. The most common local source of noise is going to be the magnetic fields generated by the power grid. So the noise is usually 50hz or 60hz depending on what country you live in.
Your body becomes an antenna. Sometimes you can actually hear a radio station (very quietly) this way!
It's the sound of a million audio engineers crying out in pain at whoever thought it was good to make a connector with the signal on the tip and ground on the sleeve.
Other people explained why, I just wanted to point out that it's mainly the fault of poor design, and relatively newer connector formats like XLR avoid this issue. Ground connects first is now the rule.
Seeing as this thread is filled with alot of smart people I have another question.
Back in the late 90s I had an external active speaker connected to the family PC. If you cranked that bad boy up I swear I could hear what sounded like an eastern-european radio-show of some sorts. This was 20 years ago so I can't recall much detail about the pc being on or off or anything, but both me and a friend of mine agree that is what we heard.
Can speakers pick up radio-waves or something? Is there a phenomena that can explain what we heard?