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.