Nagi Nagi no Mi

The Nagi Nagi no Mi is a Paramecia-class Devil Fruit that allows the user to become a "Soundless Human". Nagi (凪) means "null" in Japanese. It was eaten by Rocinante, but with his death the fruit has returned to circulation.

Usage
The user of this Devil Fruit has the ability to create a soundproof field. The field makes that the sounds from the outside cannot be perceived from the inside. This applies in reverse too, making the sounds inside the field unperceivable from the outside.