The aim of this paper is to compare two different methods of measuring the Modulation Transfer Functions (MTF) and the corresponding derived STI-RASTI indices to assessing intelligibility. The first method uses, as test signal, a band filtered (500 and 2000 Hz) amplitude modulated noise. The second one uses MLS signals to obtain the impulse response of the system; further post processing allows us to calculate the MTF and STI-RASTI indices from this filtered respons