If you need to cover more than an acre, you can order additional speakers. Speakers are sold by the pair, and will cover an additional 2 acres per set. Each speaker set comes with 50 feet of wire per speaker, and plugs directly into the back of the unit. You can add up to 4 external speakers to each unit.
The Sonic Satelite speakers add up to one acre of coverage to the Bird Chase Super Sonic or the Goose-B-Gone Super Sonic. They are easily plugged into the side of the sonic units and come with 50ft. of speaker wire. Each sonic unit can take up to 4 satelite speakers.