guitar noise

[Suet]

Hi guys.
I'm not sure if this is a pickups or wires noise. Actually my S320 is even making hum in clear mode (when volume level is relatively high), though its level is significantly lower then in overload mode. This is not amplifier 'cause my friend's guitar doesn't make any noise on the same cable and amplifier. So I think this noise comes from my Ibanez S320. Interesting that when I turn volume up to maximum noise level is getting slightly lower.
Could anybody tell/advise something on this subject?

With respect, Suet.

[Crazy_Guitar]

You may not have your cavities correctly shielded.

[Suet]

Thanks for reply.
I opened back cover plate and it is covered with some foil. But this is it. Nothing else is shielded.
At least with foil.

With respect, Suet.