I have the hissing sound, too, and it definately is coming from the speakers at the lower end of the lcd. I think there are several sound issues with mini 9's, etc. This is one that appears to happen while the battery is charging. I have OSX on it, and simply muting the speaker, either in the OS or by the keyboard function keys, it stops. It starts up again after turning up the volume, but stopped when the battery was fully charged. It's like that annoying sound speakers make near someone with a nextel phone. And it is annoying so that is the only reason you need to consider it a flaw. I do not have good ears and do not have to have it sitting on my face in order to hear it. It is at arms length and in a room next to a room with a toddler (on hardwood) so I would not say it is not noticeable.