I have a portable speaker similar to these - Philips SPA2210, it is many years old, when plugged into the USB port of a PC, it does not emit sound.
Pros
1. Price.
2. Brand, probably.
Cons
They emit noise when plugged into the USB port of my PC.
You need to take a power supply for a smartphone, and power these speakers from it. I checked on the charger from the iPhone. When powered by it, there is no background noise in the speakers at all. Even at maximum volume.