'響' translates to 'Hibiki' meaning 'sound.' This kanji is used in both the noun and verb 'echo.'
In the story by Shinobi-dono, it is called the Sound-Sound Fruit.
In the series Batten Down the Hatches, it is called the Echo-Echo Fruit.
The Hibi Hibi no Mi is a blue, spherical shaped fruit with a spiral pattern. It's overall appearance resembles a grapefruit.
Strengths and Weaknesses
The primary strength of this Fruit is the ability to control sound. The user is able to control the volume and pitch of sound within a certain range, as well as how long the sound lasts and the direction it goes in.
Aside the standard Devil Fruit weaknesses to water and Seastone, users of this fruit must have existing sound waves to control, and cannot create sound with only their Devil Fruit. As such, Fruits like the Nagi Nagi no Mi have the ability to completely nullify the abilities of the Hibi Hibi no Mi.