I put it down to low quality chokes, but my knowledge of electrical engineering is not extensive enough to judge the safety of the brick. It sounds like a regular step-down transformer when not under load but I'd expect a neighborhood transformer to make noise, not a power brick. The periodical rhythm it makes under load baffles me. It's also kinda hot. You can smell the hot/burning plastic smell, and my ear gets quite warm while listening to the song of the power bricks.
TL;DRListen to the sounds and tell me if my power brick is in danger of catching fire, por favor.
And yes, this isn't strictly a power supply, but it's close enough, methinks.