Abstract: In measuring parameters of room acoustics, different signal processing methods will lead to different results. Based on the international standard ISO3382 and using digital measurements, acoustical parameters including reverberation times (T₂₀, T₃₀) and other quantities such as EDT, T_s, and D₅₀ are used to study and compare the influences of different filters, initial time judgment and noise correction methods on the obtained results. It is concluded that at low frequencies there is more deviation if signal-to-noise ratio is low or the reverberation time is short. Compared to ordinary noise correction methods, non-linear fitting with a middle and later impulse response function is more advantageous when SNR is relatively low.