I noticed a new feature that has caused a bit of inconvenience. New laptops including the X1 Carbon running a Realtek audio chipset will allow you to "multi-stream", i.e. play audio from both headphone jack and speakers simultaneously. However, when I plug in headphones, it usually means I want to keep my audio private because I'm in a public place. What instead happens is my music blares through my speakers and I continue wearing my noiseless headphones like a big idiot.

To fix:

Go to Realtek HD Audio Manager

Top right of the window, advanced settings

Switch from Multistream to Classic mode

Voila!