The efficiency of the sound absorbing materials made from Portland cement 1 sand and used tyre crumb rubber had been studied. The experimental conditions emphasized on the effect of thickness, ratio and grain size of crumb rubber on sound absorption coefficient. The study was divided into two parts. Part1 : Study an efficiency of the sound absorbing materials, the mixture of Portland cement, sand, crumb rubber and fresh water. The specimens with different in thickness and ratio and grain size of crumb rubber were tested to determine their acoustic properties. The sound absorption coefficients were measured by the standing wave apparatus which was followed the ASTM C384-98 standard method. The results showed that the composition ratio and grain size of crumb rubber had affected to the sound absorption coefficient with statistical significant at 95% confident. Thickness factor did not show any relation to sound absorption coefficient. The most efficiency ratio of the specimens contained small, medium and large grain size crumb rubber were 5:10:4. The average absorption coefficient were 0.24-0.27. The specific acoustic impedances were 7360.06 -8748.01. Ratio composition 5:10:4 showed the highest dominated sound absorption in high frequency range between 2000-4000 Hz. Part 2 was a study on the efficiency of the sound absorbing specimens when large grain size crumb rubber were laid separately from the cement paste. The laid crumb rubber on the surface 1 back , middle and both surface and back of the specimens had the average absorption coefficients were 0.23 1 0.24 1 0.25 and 0.26 respectively.