Turtle Helmets don't have a unique armor sound effect

Turtle Helmets don't have a unique armor sound effect, it just uses the Elytra equip sound.

How to reproduce: 

1. Get a Turtle Helmet
2. Right click to equip
3. Observe the Equip sound

Observed Results: It uses the Elytra Equip sound

Expected Results: It should have its own unique equip sound.