The ceiling

The ceiling is the more complex surface of the construction. On the floor above there are two classrooms and a corridor and some chair's dragging noises comes into the room through the slab. Another problem is the height of the room that is only 3 meters. Is very difficult to fit all the necessary isolation in the available space without compromising the effective height inside the room.
As mentioned previously, the construction can not touch the school's building in order to prevent the vibration transmissions. With this, the ceiling can not be rigidly stuck to the ceiling of the room. The solution chosen relies on wooden beams to support all the weight, fixed to the top of the sand wall.

Cut bricks to fit the beams.

The first step was to put the last row of bricks in a special way. These were cut to give space to the wooden beams. The centers of the beams are apart from each other by 60 centimeters. The beams are about 5.5 meters long with a section of 15 by 7.5 centimeters.

Cutting a brick.

The bricks were cut with a machine because they break easily if hammered and they have to be perfectly sliced, so the wooden beams fit with no gaps. We can not forget that the room have to be air tight as much as we can.

Installing the wooden beams.

After the bricks were all placed, glued to the top of the wall and filed with sand, the wooden beams were installed. The beams have only 15 centimeter and the bricks 19 centimeter.

It was necessary to put some wooden blocks to raise the beams in order to let them aligned with the top of the bricks.

Applying glue to the ceiling.

Once the beams were installed, the first layer of insulation was glued to the ceiling. It should have been mineral wool but it would be very difficult to fix it because of it's structure.

We used reconstructed foam. The acoustical performance and the price do not have any comparison with the mineral wool but for technical reasons we had to use it.

Ventilation tubes between
the wooden beams
and the ceiling.

The space between the ceiling and the beams is very narrow. The main problem is to fit the ventilation system. It was necessary to build costume ventilation tubes, but I will explain that in other post.

Ceiling isolation materials.
(test only)

On top of the wooden beams we will add an isolation "sandwich" with several materials. From top, the materials to use are:

- Reconstructed foam.

- Air space.

- Mineral wool (5 centimeters).

- Plasterboard.

- M.A.D. 4

- Plasterboard.

- PKB2 (between the wooden beams - not in the picture)

All the ceiling will be cover with this "sandwich", and will be glued to the bricks and nailed to the wooden beams.

TESTING THE ROOM

Ceiling with reconstructed foam.

After gluing the reconstructed foam all the surfaces of the room have already the acoustics characteristics expected. It doesn't isolate the sound from the outside because it has no door yet, and the ceiling it's not with all the layers, but the reverberation inside its already as it would be when its finished.

Playing music.

I have played some music inside. It sound great!

The reverberation inside its almost null, but the room it's not uncomfortable and super dry. Muting the music makes the sound disappear instantly. Other test made was turning one speakers to the wall, away from the listener, and the sensation was very similar as setting the stereo balance to the other side; most of the sound just doesn't return. It's not ready yet but is responding as expected, witch is good.

The walls

The walls are the larger areas of the isolation, and for that reason, the components responsible for the most soundproofing work. Moreover, one of the walls is the weakest point of this isolation, since it has the door.

The walls were carefully designed to fit the exact measurements of the bricks to use. The aim was to avoid the necessity of having to cut bricks. The door was also designed so it's size was the most accurate possible in relation to the brick's measures. In a normal construction, the walls are built without great care, and when it reaches the extent of the door, the bricks are cut in order to maintain the desired shape. Moreover, all the electric installation is also placed later, which means, cutting the grooves for the tubing after the wall is constructed. In this case, this technique would not be acceptable because not only compromise the wall finish, as its acoustic performance.

Another important aspect is that the wall is not resting on the floor or have any elements that connect it rigidly to the building structure.

Mineral wool glued to the exterior wall.

The first step was to isolate the outer wall acoustically. This wall is part of the building and can not be removed in order to be properly isolated. Therefore, it was isolated with medium density mineral wool, about 70kg/m3. The acoustic sense changed radically after this application; upon entering the room, almost all exterior sound disappeared, but in an uncomfortably way, because it was absorbing too much reverberation in the room: the room was to "dry".

Gluing the mineral wool to the wall.

The application was made with glue. The mineral wool is not a solid material and there are the risk of get loose, but there was no possibility of using screws to fix it to the wall. The mineral wool is there to avoid vibrations of the outer wall being transmitted, and any screw would transmit these vibrations to the interior through the head of the screw.

The second step was to prepare the surface on which the wall rests. The inner wall is floated so there is no vibration transmition from the building to the wall.

First row of bricks to set the alignment.

One row of bricks was place and adjusted like the design on the project. Note that the door frame was previously built and used to perfectly align the bricks. With reference to this alignment, the felt was cut and placed on site with the first brick's row above.

Glued bricks.

After some tinkering and small tuning their positions, the bricks were fixed with glue between them.

Adding sand to the brick.

After the glue cure, the bricks were filled with sand. The process was repeated on each row to the top.

Boxes and tubing for the power sockets.

The technical boxes and tubes for electric sockets were installed when the elevation has been reached, thereby preventing further opening of the wall. Note that the brick is already the finished wall and therefore can not be damaged.

Four bricks were drilled with the diameter of the boxes for the outlets. These were fitted with tubing connection therebetween, and then cemented to maintain the boxes fixed. There are only four bricks with cement across the structure.

Do not forget that this structure is very heavy. Each wall is about 5 tons and does not cause damage to the building because underneath there is the planet earth. It would never be possible to build this room on the first floor without structurally reinforcing the slab. This weight can damage the building if it is not prepared to endure such a weight.

If the studio had to be built up at the first floor, other isolation technique had to be used, lighter, but at the same time, bulkier and more space consuming.

Preparing the room

Preparing the room

The room where the studio is built is square. Had electrical outlets, light switches, technical boxes where the electrical, alarms and communications cables pass, and two windows.
After removing all the school equipment, such as tables and chairs, all the technical boxes were dismantled and taken away. Cords were removed from the interior of the wall and the empty boxes have been filled with foam. Four boxes however, could not be removed because they are part of the emergency and communication circuits of the main building. Two of them were rebuilt facing the other side of the wall, since they are in the interior walls, and so, with access from the corridor and from the next room. The other two could not be turned due to the wall being outwardly. Two small doors were added to the sand wall so we can access the boxes in the future without having to demolish the wall.

Closing the windows with

sand bricks and cement.

The windows were closed with brick and cement.
On the other side of these windows is where the students gather together at class's break, and they make lots of noise. The exterior wall has 40 cm of thickness but the bricks only have 15 cm.

Filling the brick with sand.

The bricks were filled with sand to reinforce the isolation with the outside.
The sand acts as an absorbent once the sound energy has to bounce from one sand grain to another, thousands of times inside the brick, and this kills the energy. The sand also destroy the air cavity inside and the brick no longer resonate.

Mineral wool on the exterior side

of the closed window.

On the outside, a 5 cm layer of mineral wool was added before the finishing plate. This is another layer of protection against the sound energy. The sound that will be able to reach the bricks, will be so weak that the sand bricks will have no "work hard" to prevent the sound entering the room. The rest of the wall its a double wall with brick on the inside and reinforced concrete on the outside.

Metallic door´s frame
aligned with the
room's door.

After the room was empty, the sand wall position has been marked on the floor and aligned with the outer door.
The door is the weak point of the sand wall, with respect to acoustics.
The door frame was built first so that the wall could be perfectly integral with it. This, ultimately enhances the way the wall is related to the door and its expected insulation.

The project

This project is to build a sound proof room, with controlled acoustics to be used as a sound recording studio at ESAD College of Art and Design.
The main objective is to create a comfortable space where the school's noise do not interfere with the silence needed to record and edit sound.

The room has twenty seven square meters of free space. The inner wall is made with split brick filed with sand and it is floated. The floor is a structure made with wood and sand, with carpet on top, and floating foam at the bottom. The ceiling is completely supported by the sand wall, and do not touch the building. It is made of wood, plasterboard, M.A.D4, PKB2, and mineral wool. The door is made of solid wood and mineral wool, with eight centimeter of thickness.
The room also has an ventilation system made with silent motors and conducts, mounted two floors above, as far as possible.

One important aspect of this project is the weight of the structure. The sand wall and the sand floor are too heavy, and it is only possible to build this because it is located on the ground floor. There are others methods to insulate a room, with less mass, and more suitable to build on higher floors, so beware! If you intend to use this technic, always do all the math and ask an engineer for a professional opinion, or you can damage the building in an tragic way!

Next post: Prepering the room.