I recently bought an Ibanez EDA900, and it's great. Only problem is, after what seems like no difference in atmosphere, and no knocks, there is a hissing sound coming from the magnetic pickup. It sounds like a fizz/static noise, that only sounds when the strings are played. The louder I play, the more prominent the noise. I think it might be either something loose inside the bass, or maybe just a need for a new battery (though the volume is constant and there is no distortion)

Any ideas to what it could be/how to fix it?
Also when I plug the cable into the bass, the hissing sound starts really loud then dies down, if that helps in any way. Thanks in advance for any help.
First, change the battery. If that fixes it, then it is a cheap and easy answer. If it has no effect, you've probably got a loose wire connection inside. Have a tech check it out and have him or her make sure the ground is good also.
"Maybe this world is another planet's hell?" - Aldous Huxley
I've changed the battery and raised and lowered the pickup to no avail. Looks like a trip to a guitar tech. Thanks for your advice!