Identify new icon

I just noticed a new icon when making outgoing calls. It's in the upper right hand corner on the left side of the volume icon and it's square that's blue and black that is devided by stars.
Anyone know what this icon means?

Thanks

Its for enhanced audio while in a call, while in a call you can hit menu and then hit enhance call audio, you will see the icon display. I am not 100 percent sure why it displays on its own sometimes.....

Can you hear the difference when it's on and off?

I have never tested it. Without it I hear fine :)

Call someone and menu over to it as I posted above and test it out. You can adjust treble etc etc....... Enjoy

awesome thanks.