Weird "Howling" Meow???

The howling may have something to do with the fact that he's a Himalayan MALE! I have a Siamese male and a Siamese/Himalayan male, as well as a gray tabby male. The Siamese and the Himalayan howl/sing for quite awhile at night. They also prowl around, like they're looking for something/someone. You know that cats are nocturnal, so when it gets "nighttime", they're ready to prowl. For some reason, my gray tabby male doesn't do this, so that's why I'm thinking it could be the Himalayan in yours that causes this. Also, since cats have such extremely good hearing, he may be hearing something at a great distance, that you can't hear...train ?....something that happens every night at the same time. Do you have him shut out of your room? Maybe his previous owners let him sleep in the bedroom with them? Good luck........