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Hello, this is Dr. Jess. I am sorry to hear about your cat! It sounds like he could be having trouble adjusting to his new home. I would be sure that he has access to places to hide (rooms where he can be alone or boxes he can hide in), and that his food and water are somewhere that he feels safe- you could even provide more than one spot for food and water to start out with- be sure one is not right out in the open/the room with lots of traffic (people tend to put it in the kitchen or other high traffic areas and he may be nervous to spend much time in those areas right now).
You can also pick up some products at the pet store/your vet/or online that may help with some anxiety. There is a feline pheremone called Feliway http://www.petco.com/shop/en/petcostore/product/comfort-zone-diffuser-refill-with-feliway-for-cats, which plugs in like an air freshener and can have a calming effect in many cats. I would also consider a calming supplement like Zylkene or Composure. https://www.amazon.com/VetriScience-Laboratories-Composure-Feline-Bite-Sized/dp/B003KV7XVA, https://www.amazon.com/Vetoquinol-Zylkene-75mg-30-capsules/dp/B00GYHPAFI/ref=sr_1_1?s=pet-supplies&ie=UTF8&qid=1480090053&sr=1-1&keywords=zylkene+for+cats.
I would also keep an eye and make sure kitty is eating and drinking and urinating and having bowel movements. If you notice he is not doing these, then there could be a medical cause for his vocalization (not urinating at all in a male cat is a medical emergency).