How to get my dog to start barking?

I have a shetland sheepdog who will bark at anything he sees. It's really annoying when I try to do a baseball drill in my basement or outside and all he does is bark and bark until about 30 seconds later my parents come down or outside and chew me out. I really need to do these drills if I want to get better. If he comes down with me, all he'll do is stand right in front of me or jump on me like he WANTS to get hit by the bat or something. Please help.