Why does my Qi charger hiss?

[AC Question]

My new qi charger is making a sort of hissing noise when charging my phone and when connected to the wall via the samsung adaptive quick charging brick.

 

[Chris Parsons]

I'm not sure of the science behind it but it's not uncommon according to various other threads here.

http://forums.androidcentral.com/google-nexus-5/339991-wall-charger.html
http://forums.androidcentral.com/verizon-droid-dna/254195-wireless-charging-buzz-hum-whistle.html
http://forums.androidcentral.com/go...ion-does-your-charger-emit-hissing-noise.html