NOTES AND DISCUSSIONS
299
from the ceiling and the floor; it is not even connected to them by nails. The
partition is held in position by being nailed to the heavy layers of hair-felt, which
in turn are nailed in place. The flooring and the ceiling between the two sides of
this wall are broken, as shown in Fig. 3, so that they will not transmit vibrations
to the inner room. The ceiling is isolated by means of a 16-in. layer of sawdust,
lath and plaster, and a layer of insulite. The floor upon which the inner room
is built is isolated from the room below by means of ceiling boards, lath and
plaster, 16-in. joists and air spaces between them, rough flooring, hard wood
tongue-and-groove flooring, and sheets of slater’s paper. The construction of the
side walls is shown in Fig. 4. Overlapping sheets of slater’s paper are spread over
the stone wall; then there is a 2-in. air space and a layer of insulite.
Fig. 5. Detail op the Floor-Supports of the Soundproof Room
The inner room is completely surrounded by an air-space. A 4-in. air-space is
left between ceilings and, as shown in Fig. 2, between the walls on three sides.
On the fourth side there is a 4-ft. passageway. The floor studding of the inner
room rests upon five 4 x 6 in. joists—only two of which are shown in Fig. 3—which
in turn rest in felt and metal gutters. The detail of these gutters is shown in
Fig. 5. Four layers of one-inch hair-felt separated by sheet-iron valleys support
the joists. The purpose of the felt and metal gutters—as of the entire floor con¬
struction—is to eliminate vibrations. Across the 4x6m. joists is a layer of
insulite, and over that is placed a second set of joists (2x6 in.) at right angles to
the first. The outer wall and ceiling of the inner room are supported by these
joists. They also support, by means of rope hammocks made of 1 /2 in. hemp rope
and held in position by staple irons, a third and parallel set of joists, which in turn
support the floor and the inner walls and ceiling. The floor is made of tongue-
and-groove hard wood. The space between the floor and the insulite sheeting
nailed to the other side of the second set of joists is filled with sawdust. The
outer and inner walls and ceiling are covered with insulite, and the spaces between
them are also filled with sawdust. The room is to be lined with a sound absorbent
and the floor covered with cork-linoleum and rugs.