once the big hole was dug and the surrounding hillside, house, and pool were shored up with cement barriers, it was time for the foundation. at our location granite is very near the surface, so it was possible to proceed straight to laying out rubble, followed by gravel. then came a first layer of thermal insulation and moisture protection. thereafter various layers of rubber were layed down for the 150 square meter (1'650 sq ft) recording room to rest on. incidentally, all of the walls are also coated in a layer of rubber. the reason for this is to attenuate (and hopefully eliminate) very low frequency vibrations emanating from the rail line which passes 15 meters from the studio's east wall. as a final step before the pouring of the concrete substratum of the floor, steel armature was laid out in a grid pattern.