Welcome aboard, Melissa! Your whole family is in for one very magical sailing aboard the
Disney Fantasy next month! I bet you are already counting down the days!
Disney's ships each have Disney-themed horn songs that are played when leaving ports of call and a few times throughout each sailing. I get a bit teary-eyed when I hear "When You Wish Upon A Star" ring out from the ship's horn! It really is a magical way to begin each cruise!
It's a great idea to prepare your son for that noise, as when you're on deck, it can be pretty loud. However, the good news is that if you're inside the ship, you may not even hear it go off. Staterooms with Verandahs will have a better chance of hearing the horn, though muffled if the door is closed, but anywhere else farther inside the ship, and most likely you'll miss it altogether.
Usually the horn sounds when the ship leaves a port, including during the
Sail Away Party on the first day, and sometimes around noon on the sea days after announcements are made, and during the
Pirates IN the Caribbean Deck party when I've heard the horn play "Yo Ho Yo Ho, A Pirates Life For Me". You may wish to stop down to Guest Services when you first board to inquire about when to expect the horn on your particular sailing so you can better prepare your son.
I hope those details help as you continue planning, Melissa!
Have a great cruise!
Marcy