Usually in certain applications when air flows over the jute fibers at grazing inci­dence, at times the fibers may come out of the jute felt with the airflow. In order to prevent the fibers from separating natural rubber is sprayed on to the jute felt sur­face. However, this coating of natural rubber may close some of the pores of the jute felt and thus decreases its sound absorbing capability. Thus rubber spraying has to be done with caution. Table 6.10 shows that untreated jute felt (density 117 kg/m3) has higher NRC value (0.85) as compared to 1% natural rubber latex jute composite (density 219 kg/m3).