Could be an equipment or an operator issue or both. Squeaks happen for many reasons, but the root cause is always that the reed vibration is disrubted for one reason or another. Regardless, I would recommend going to a hard rubber mouthpiece. If you're a beginner alto player, check out a Meyer 5MM, Vandoren V16 A5M or Optimum AL3, Selmer S80 C* or Selmer S90 (180 or 190). Also make sure your reed is positioned on the mouthpiece so the tip profile lines up perfectly with the tip profile of the mouthpiece. Also, be sure you are soaking your reeds for at least 10 minutes before trying to play and that there is not a warp in the tip (tip doesn't look wavey).

If you do all of this and still have a squeak, then you need to consider operator error. The best suggestion here is to take a lesson with a trained saxophone teacher who knows how to assess embouchure and can teach proper tone production. Best of Luck!!

Cheers,
     Mark Overton
     www.saxquest.com