I bought a macbook pro 15 yesterday and have been playing music on full volume straight out of the box. Now with the majority (70%) of songs everything is fine. However, some songs cause a faint rattle/distortion type sound on the left speaker. I have moved the slider to both the left and right speaker and the problem does not occur in the right speaker; only the left. It is not unlike the sound when you turn the equaliser on any small speakers to max and there is a kind of stress on the speaker. However I am just listening to normal songs and at max volume. I noticed it stands out more with low quality audio. It is not all that noticeable but it can be annoying when it pops up on certain songs... but it is subtle. Im not sure if this is normal. I don't want to go to the shop and have four apple sales assistants crowding round trying to hear the problem; I'm also far away from the apple store so it would be difficult.