My ideas - I have a couple of snakes that only pee in their water bowls...looks like a ball of yellowish snot with some ribbons of it...not sure this is the same for you. If it was mucus then when you picked him up you would surely see it in his mouth since snakes can't cough it up.

Also, if the sound has been going on for 10 days and it loud enough for everyone to hear constantly then you should easily be able to tell if it is the snake or not...as he would be doing it all the time.

I would get him out and just check him out...look for mucus (use a Qtip to look in his mouth) and just listen to his breathing. Any mucus or wheezing and I would get him to the VET ASAP as his RI is very far along.

If not then you really need to figure out what the sound is...it could be some sort of electrical short that is arching and so you don't want a fire.