ROCKWOOL Rockboard 40 and Rockboard 60 are three densities of mineral wool board insulation available to support a variety of interior applications, including insulating mechanical or utility rooms, adding also a barrier to noise and fire. Rockboard 60 in particular has been used for sound studios and theaters, as it has exceptional sound absorbing characteristics and is effective at reducing sound transmission across a wide range of frequencies. Formerly known as Roxul Rockboard.