Hi there... I had the same problem and have sent a reply into Jonathan. I wasn't sure if my reply would be visible to you but I have copied and pasted below the message sent as it may be beneficial for apple and its communities to be transparent about the issue. I feel my 'noise' issue in the watch was created by the new version upgrade (but unsure). Did you have a similar experience?
" Hi Jonathan. Thanks for this thread and your reply which I read with interest since I had the same problem on my watch which was purchased only 3 weeks ago.
I did the re-start and the noise seems to have gone for now.
However, can Apple be transparent and advise if the real nature of this issue since it seems to be experienced by a number of users? My watch was running on the previous operating version and I have updated to the latest version a couple of weeks ago.I cannot say for certain (as I can't remember) but it's likely that this noise issue has started only after the recent upgrade.
Please advise. "