To prevent noise in punching by placing a sound absorbing material to be put on the inner face of the cover, frame, etc., of the machine, in a staggered arrangement in which the adjacent patterns are different vertically and horizontally from each other, and designing the sound absorbing material to be of a four projection composite type rugged pattern.

A rectangular material, in which a rugged pattern is formed on the surface of a sound absorbing material, is quadri-sected in grid shape, to form a staggered arrangement in which the adjacent patterns are different vertically and horizontally from each other, and is designed to be the sound absorbing material 7 of a four projection composite type rugged pattern. It can also be designed to be the sound absorbing material 8 of an one projection single type rugged pattern, freely cut into a prescribed size, and placed with the pattern direction freely set. When a workpiece placed on a table 5 is worked by moving a striker 4 vertically through the action of a cylinder 3, the striking sound vibration are generated and propagated in all directions. However, the four projection composite type and the single type sound absorbing material 7, 8 are placed closely in a zigzag on the inner face of the cover 1 and the frame 2; therefore, the noise and the like are absorbed, greatly suppressing the leak outside.