Study on the optimal stack diameter on the efficiency of thermoacoustic engine by Irna Farikhah, Irna Farikhah, E. A. Elsharkawy, E. A. Elsharkawy, Harto Nuroso, Harto Nuroso, Mega Novita, Mega Novita, Dian Marlina, Dian Marlina, Kwartriani Rahmatunnisa, Kwartriani Rahmatunnisa, Abd. Rahim, Irfan, Md. Zain, Mohd. Zarhamdy, Mohd. Paad, Khairunnisa, Masruri, Ahmad Nadhif