Q: Muting/Unmuting a call?

Is there any way to mute/unmute a call besides unlocking the phone, opening the phone app and hitting the mute button on screen?    It's very annoying when I quickly need to mute/unmute a call (dog barking, etc.) to have to go through those steps.    Is there an external mute button or a mute button on the earbuds?  I had that with my old blackberry, but can't figure it out with the iphone 5s.  Thanks.