audio

I have a macbook (2.4 Ghz Intel Core 2 Duo 4 GB 1333 MHz DDR3 Macintosh HD) and the sound of it not working, so if I connect a sound box. What can it be? He stopped suddenly and I'm on the inside does not have a service center nearby. I need help. I'm in the state of Minas Gerais in Brazil, if anyone can answer I thank you in Portuguese, but, okay, I give it my way. Thank you! I await!