the feasibility of using impedance tube with two microphones and sound absorption coefficient measurement of iranian-made materials using transfer function method

background: sound is one of the most important factors threatening workers’ health. the most efficient and practical method for controlling noise pollution is the use of sound-absorbing materials. impedance tube with two microphones is used to determine the sound absorption coefficients and should be tested periodically for accuracy and efficiency. the purpose of present study was assessing the feasibility of tube performance and measuring the sound absorption coefficient of some iranian-made materials. methods: after designing the impedance tube and ensuring its effectiveness via comparing the measured chart with the reference curve of standard foam, the absorption coefficients of four samples including glass wool (15 kg/m 3 ), mineral wool (40 kg/m 3 ), cork (390 kg/m 3 ) and rubber (89 kg/m 3 ) were measured in two different thicknesses. each sample measurement was performed three times and then, the average results were showed as graphs using va-lab4 software. findings: the results of the accuracy and efficiency showed that the impedance tube could be used with a correlation coefficient of 0.98. in addition, the glass wool sample and mineral wool had the highest absorption coefficients and the cork and rubber sample had a lower sound absorption. besides, comparing glass wool with reference values showed that in both samples, the absorption increased with increasing frequency. the measured mineral wool with greater thickness had better sound absorption in all frequencies except of 2000 to 3300 hz. however, the reference mineral wool with 50 mm thickness had lower absorption in frequencies of 2000 and 5000 hz. conclusion: according to the results, the absorption coefficient can be determined with the highest accuracy for all materials via 2-microphones impedance tube and in this way, we can achieve the desired results of controlling noise pollution in environment and industry.