My phone (LG G3) shows two different types of headphone icons. They are the leftmost icons in the images below. The first is a normal headphone icon. What is the second one?

I think it might be USB headphone, but that doesn't make sense, because I don't have USB headphones and never use USB headphones with the device.

I have noticed sometimes when I use the aux cable for my car, it displays the second icon instead of the first one. It shows the first icon whether I use headphones with a built-in mic or headphones that don't have a mic - it's the same icon.

Image 1: normal headphone icon

Image 2: ??

Any thoughts?

Edited images to make them smaller