I used to have the "rice crispies" sound in my neck all of the time.

Mine was mostly from repetitive & forward head work postures - it puts added strain on the c spine and neck muscles. {age 48 at the time}

A very good chiro helped with a lot of my RSI/TOS & some alignment issues.
I only get very minor sounds now if I do a lot of heavy or strenuous chores - like stacking hay or rototilling the garden - did both this weekend.

Are your neck muscles tight or do you limited range of motion in your neck or shoulders?
Are you at a desk or computer often, or even doing a hobby, with arms & head forward of the body?
If so those could be a cause of the sounds.