The Accuracy of Speech Transmission Index Estimation under Conditions of Joint Action of Noise and Reverberation

In this paper, the full modulation method of speech intelligibility index (STI) estimation and its modification in the form of the full formant-modulation (FM) method are compared in terms of measurement accuracy in conditions where the speech signal is masked by noise and reverberation. Dependences of STI estimation errors on signal-to-noise ratios and on the duration of test signals for the reverberation time typical for university auditoriums of 0.8 s were obtained. It is shown that the accuracy of STI estimation in the presence of reverberation practically does not depend on the choice of estimation method. The obtained results indicate that an acceptable for practical use error of 0.01-0.02 of STI estimation in the conditions of joint action of noise and reverberation can be ensured when using test signals lasting 8–16 s.