When using full volume on my iphone 4s sounds cuts out but if I blow air into speaker it comes back on this hardware issue or software issue

Just recently my iphone 4s speakers started acting up. I have restored it twice once to a back up and the other time as a new phone. The speakers get really staticy on full volume and then it cuts out but if I turn down the volume and blow air into the speakers it goes back to play fine until I turn up the volume again. I'm going to try to clean it out with a toothbrush and see if that helps. But I'm curious does this seem more like a hardware problem or is it a problem with the operating system and I should try to hold out until ios 6 comes out and see if that helps. I've read all the problems with this so I'm hesitant to send it in since there is no apple store around here and find out I have to pay to get it fixed. Tried to talk to them on the phone but since it's a week past ninety days I would have to purchase apple care in order to get any help but yet that's only available for 30 days after your purchase so I'm not sure how come they can offer that over the phone. Thanks for any help.