@benjojo You'll also need to be very careful with the hardware design with such a thing -> USBs physical layer isn't quite symmetrical, frames are separated by pulling both D- and D+ to the same potential. Because USB frames are sent at 1 (or 8 for USB HS) kHz, you'll get a weird high-pitched noise if you have any leakage/interference from the USB lines at all.
I'm sure most people reading this have heard it before but probably didn't know why: https://0xstubs.org/understanding-usb-microphone-whine/