The ornamental design for wireless acoustic box, as shown and described.
FIG. 1 is a perspective view of the wireless acoustic box of my design viewed from the top, and left front corner, showing the top, front and left side;
FIG. 2 is a perspective view thereof viewed from the bottom front, showing the front;
FIG. 3 is a perspective view thereof viewed from the top front, showing the front and top;
FIG. 4 is a perspective view thereof viewed from a top rear corner, showing the rear and right side;
FIG. 5 is a perspective view thereof viewed from the top, and right front corner, showing the front, top and right side;