thanks ericbalajadia for the response. like you've said, there are two possible major culprits- tires or wheel bearings.. haist. it seems to be coming from the rear. if its the tires, why is it that i only got to notice it now and the weird thing is those with me during the ride said they haven't heard any high pitched humming when i broached it to them. so i brushed it off as due to whatever ear sensation felt during long travels.. hehe. but i can't seem to get it off my mind so here i am.

anyway, i did notice that there's an uneven wear on the rear tires (low profile dunlop 16" by the way) especially on the outer side where there appears to be faster thread wear and medyo kalbo na yuong sides, though it has been so for quite a long time already. wala namang kabig ang manibela but it's really not full proof of misalignment of the weels as i've been told. i guess might as well bring it to casa for proper inspection and for peace of mind na din. maraming salamat po.