Death From Below - Call of Duty: Black Ops II - Vengeance DLC

In Buried, drop the beat on Zombies 10 times - 10

Firstly you will need to build the Subsurface Resonator.

All parts can be found in the General Store:

Roulette Table

Motor

Speaker

Mount

Secondly you will need to build the Generator, as the Subsurface Resonator needs a power source, it does not run off of the main power supply.

All parts can be found in the General Store:

Fan

Tail Fin

Mannequin

These will have to be built on separate Craft Tables. This can be tricky in solo, it is easier doing this with a partner.

Zombies will be attracted to both devices, destroying them, meaning you'll have to pick up another one.

Place the Subsurface Resonator done first, then the Generator near by.

The Subsurface Resonator blasts out a sound wave; killing zombies on lower rounds, while only knocking them over in higher rounds.

You need to kill/knock over at least 10 zombies. 

Subsurface Resonator