Question

Question B1 A building material X transmits 1% of the sound energy incident upon the wall under centre frequency of 250Hz. Another building material, Y has transmission coefficient of 6 x10? Define and calculate the sound reduction index R of materials X and Y at this frequency. Which building material has better sound insulation? Given that the threshold of hearing intensity Io = 10-12 W/m? (Correct the answer to 4 significant figures) (10 marks) 1

Answer 1

The sound reduction index (R) is given byer te transmission coeff. R = 10 los 10 log (it -12 elů Transmitted inteneity Io = 10-12 W/m ( given 1% 10 = 0.01710 = 16" Wilmi ta - -14 lo 0.01 loti te 6X100? Rez 10108 (60) 16x 2 = 20 For material y given R = lolog to log tokio Since sound retelelson is more in X, it acts as better sound insulator 12:22 a