# [Physics] Speakers and Static from Hands

electric-currentelectricityelectrostatics

Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?

First off, what you describe only happens for highly amplified speakers. The current change when you touch the wires is pretty tiny and you'll only hear a sound when that signal is being amplified significantly before being sent to the speakers.

There are many reasons why a tiny bit of electric current flows from your body to the speaker wire so I'll only list a few off the top of my head:

• When you first touch the wire any static electricity can flow to the wire which could make a loud pop
• Air moving over your body provides a constant source of static electrons which can flow into the wire
• Sweat and salt can act as a tiny saltwater battery between your fingers and the wires
• Your body produces tiny amounts of electrical current (this is how your neurons work)
• Your body can act as a giant inductor for the $50$ or $60$ $\mathrm{Hz}$ electric current from the power grid (and therefore changing magnetic field) surrounding you
• Your body is a (poor) antenna for the radio waves passing through you
• The "ground" your body is making contact with may have a tiny varying potential which would allow current to flow from the wire through your body to this ground (and vice-versa)
• The speaker wire is typically two wires right next to each other that act as an antenna. if you touch only one of the wires you act as a ground allowing induced current from radio waves to flow through you to the ground

Without a lot of experimentation it's hard to know which of these are the significant sources of electric noise and of course, there may be others I didn't list.