If you want to mute sound Instagram stories then you must follow these steps:-
1. First launch the Instagram app on your mobile device and then log in to your account.
2. Then swipe right from your home feed or tap on your profile picture to access your own stories.
3. Then create a story and before sharing you can mute your story’s audio by tapping on the Speaker icon which is located at the tap of the screen.
4. Then finally tap on the Your Story button to post your story without sound.