Almost certainly speaker wire or something similar acting as an antenna. You can find videos of the phenomenon on YouTube. The creepy voice would just be down to distortion; it can sound a lot like someone is using a voice changer, as though they're a movie villain making a phone call.

I wouldn't put much stock into what the phrases sounded like. It's easy to misunderstand distorted speech, especially when you're primed to hear something weird or spooky. The repeated "duct tape, duct tape" seems like what one would expect from someone using a walkie-talkie, where repeating words for the sake of clarity is common. E.g., "all stations, all stations, blah blah blah...".