It's noticible... Obviously it's going back as it wasn't put in the description that it has coil whine.
So it was miss sold and miss advertised.
Best of luck. Thankfully I had no issues with the returns and refunds etc with the 27" monitors I had bought, the first return being made on a Saturday night for a collection and replacement first thing Monday AM.!. It took three before I got a keeper. Thankfully all done and dusted in less than a week with full refunds etc.
When you are buying hardware it can sometimes be a lottery, that is when you need to find a good etailer to work with you.