Blind method of estimating speech transmission index in room acoustics based on concept of modulation transfer function

Abstract

The speech transmission index (STI) is an objective measurement that is used to assess the quality of speech transmission in room acoustics. This paper proposes a simplified method of blindly estimating the STI in room acoustics based on the concept of the modulation transfer function (MTF). STI can be estimated with this method in four steps: (1) MTF is estimated in the whole band from the reverberant signal without having to measure room impulse responses (RIRs), (2) parameters of the RIR, TR and a, are estimated in the whole band by using the estimated MTFs, (3) RIR is estimated from these parameters based on Schroeder's RIR model, and (4) STI is estimated with the algorithm in IEC 6026816:2003 from the estimated MTFs in the seven-octave bands. Simulations were carried out to evaluate the proposed method to estimate the STI in both artificial and realistic environments (43-realistic RIRs from SMILE2004 datasets), by using artificial AM signals to verify the concept and by using speech signals to confirm whether the proposed method was possibility to implement. The results revealed that the proposed approach could be used to effectively estimate STIs without measuring RIR by using observed signals such as speech signals.