Power adapter making high-pitched sound when using magsafe

Hi there, so I’ve been using the Apple 20W adapter with a magsafe charger to charge my iPhone 12. Everything’s been working fine for the past couple of months but recently, the adapter has been making high-pitched sounds when my phone is charging. The weird thing is, it only does that when I’m using magsafe to charge my phone; using a charging cable doesn’t activate the high-pitched sound. Is there any explanation or fix to this apart from replacing the adapter? Thanks.