Hello. No matter what sound plays on my phone, it only uses 1 speaker. I don't have any song on it, but I tried it with some youtube videos and there is only 1 speaker working. I tried covering the one that's playing and I can not hear very well while it's covered, plus my finger vibrates. When I cover the other one, nothing happenes. There is no difference in sound and my finger doesn't feel a thing. However, when I plug in the headphones(stock)...they both work. P.S. Where is the microphne located on the 3GS?