Jute, cotton, coir, flax and their derivatives can be used as acoustical absorber in walls and ceilings of buildings. Such application of the biocomposites helps in con­trolling the reverberation time and the SIL. A typical case study using jute is pre­sented here. Raw jute fiber, chopped jute strands and jute felt as shown in Fig. 6.3 can be used for wall and ceiling treatment. These jute derivatives can be held against a wooden board and faced with a perforated sheet or kept inside a jute cloth packet. The sound absorbing properties of such sample varies with thickness as discussed earlier. These jute derivatives can also be used in office partition and cubical ceil­ings. Since these materials cannot be put by themselves onto a wall they have to be kept inside a jute cloth packet which can be either glued or stapled to the wall. Some of these jute cloth packets can be stapled or screwed against a hard backing surface as shown in Fig. 6.15.

FIGURE 6.15

Natural rubber based jute fiber composite panels have adequate transmission loss and can also be used as partitions in office cubicles. The transmission loss of such panels can also be measured as per ASTM E90 standard38. They also have adequate amount of flexural strength and can be used in such application. A typical used ofjute fiber based panel with a perforated facing of 47% open are ratio used in our office cubical for noise reduction is shown in Fig. 6.16

Typical board size are 600 mm x 600 mm with a thickness of 50 mm. Figure 6.17 shows such boards being used in a room ceiling for controlling the reverbera­tion time. Such jute boards can also be fixed on auditorium walls for improving the acoustics. These boards can be either screwed or nailed into the backing wall at the
corners. These materials have good thermal stability properties and are fire retardant themselves, thus can be safely used56.

These boards have been used in ceilings of rooms for more than three years and have no signs of degradation in their physical condition. Depending upon the requirements, these acoustical boards can be made of larger dimensions for instal­lation in the walls of auditoriums, cinema complexes, shopping malls, hospital, li­brary and airports.