Summary:

EDIT: Apparently, there is a bug MCPE-96015 that prevents all items from making burning sounds in lava including nertherite items so this bug is kind of fixed.

All netherite items make burn sounds when they are in lava. The items themselves don't disappear but they just make burn sound. They shouldn't do that as they are lava resistant

Repro Steps:

1. Get some netherite items on creative

2. Throw the items in a lava pool

Observed Results:

You will hear some burning sounds from the lava but the items isn't affected. The sounds don't stop and they increase by throwing more items into lava.

Expexted Results:

Netherite items shouldn't make burn sounds in lava as they don't burn.