I've been on Lamictal for a few years, haven't had this, in fact I have never seen any info that hallucinations as a side effect of Lamictal.
You may want to pay a visit to an ENT, have the ear doc check it out, it can be something happening in the ear canal and/or eardrum.
Sometimes I can hear certain sounds that the rest of the family can't, but my dogs do. 9 out of 10 times I'm able to track down where it's coming from, usually it's some kind of "house" sound,furnace,sump pump,appliances,machinary outdoors being used. Try not to get worked up, thinking it is hallucinations, most likely isn't. Take it up with your doc, to rule out anything.
Lots of luck with this.
Take care,
DE