The camera has an actual mechanical shutter. You will not be able to take non-noisy pictures. How much of this noise is attributable to the sound file and how much is attributable to the shutter I don't know.
I but if you set your phone to the silent profile it won't make the shutter sound anymore, that is how the Sony Ericsson K790a works, and I know its OS is based on Sony's version of symbian. Its not really a solution, but a work around.