Based on the commonly used indicators for speech intelligibility,this work acoustically evaluates the two largest auditoria in the Faculty of Engineering,Helwan University,Cairo,Egypt,using experimental and digital simulation techniques.Design treatments were also suggested to improve the acoustic performance of the auditoria,where the impact of these treatments was checked using the simulation as well.The models that were analysed using the CATF software were first validated utilizing the results of the field work in the unoccupied rooms.The results showed that the acoustic quality of the two auditoria are far from the optimal conditions due to their improper acoustic characteristics and the high noise levels as well.The results of improvement proposals showed that altering the ceiling shape and adding efficient absorptive materials to the rear surfaces successfully reduced the excessive reverberation time to the optimal values,increased the early reflections and eliminated the shadow zones.In addition,decreasing the noise levels by 20 dB due to improving the window insulation noticeably improved the speech intelligibility at all receivers.