What I did, was take my mp3 player and put on a bunch of Varmint Al's sounds on it and hooked it up to the Cass Creek Bighorn speaker that I purchased from Sportsman's Warehouse for about $40...it operates on I think 4 C cell batteries. So since I already had the player, it was a pretty cheap way for me to go. But if you don't already have one, they are pretty inexpensive, and you can get them just about anywhere.