Snakes often make noises - especially when they are being held or messed with - that emanate from the glottis and the nares. These are usually the expulsion of breath due to stress.

Occasional situational whistling/crackling/static from the glottis is normal, and is a by-product of the shape of the glottis X the rush of air forced through it. It is completely normal and is nothing to worry about.

Since you mentioned that this sound came from the snake when you were holding it - and coupled with the fact that there were no other symptoms - I would hazard an educated guess that he did not have an RI.

However if you amp up his heat and add moisture to a closed environment that is only occasionally fully disinfected of it's fecal matter - you can probably count on fighting some sort of infection in the future.

Ball pythons are fans of relative humidity. Spritzing the crap out of tupperware tub or wetting the heck out of the substrate does nothing but create ideal breeding conditions for bacteria.