The Bug:

Turtle Helmet, diamond, gold, chain, iron and leather gear play the corresponding minecraft:item.armor.equip_<X> sound when they lose durability when the player takes damage while swimming in lava.

How to reproduce:

1) Open a world with cheats

2) Give yourself any of the above, for example give yourself golden leggings

3) Give yourself a lava bucket

4) Go in survival mode

5) Go for a hot swim and take notice of the sound being played every time the leggings lose durability