Let me guess, its 'within spec'. I have similar on Prime PSU - its even been compared next to another Prime PSU that was totally silent - just as I expect them to be
I didn't get that far! The dealer got in touch with Meridian, Meridian emailed to ask me about whether I had tried it in different sockets. I then played around with sockets for a bit and replied to say it made no difference at which point they went silent, despite repeated emails from me asking what we should do next.
It's difficult to say what it causing it, but I can say it is coming from the LED display at the very top of the unit. I wonder if there is a transformer hidden in that circuit?