How to automatically switch to HDMI audio when closing lid on macbook air?

I used to have a Samsung Laptop, and when connected to my 50" HDTV, all I had to do was close the lid to switch displays, but it would not only switch displays, it would also switch to HDMI sound for the TV as well. Was nice and seamless. But with my Macbook air, I have to manually change audio BEFORE closing lid. Any way to eliminate the step and make the whole process more seamless?
Any help would be greatly appreciated -- thanks in advance!