Broadband interference in speech reinforcement systems

The paper undertakes underestimated problem of influence of the number and distribution of loudspeakers in speech reinforcement systems (SRS) on the quality of publicly addressed voice messages, namely the speech intelligibility in auditory rooms. Linear superposition of time-shifted broadband waves of the same form and slightly different magnitudes that reach a listener from numerous coherent sources, is accompanied by interference effects leading to a deep modification of the received signal waveform and, consequently, of its frequency spectrum. Signal transmission in a multisource SRS and distortion of fundamental voice elements (phonemes) have been simulated and analyzed with the use of linear time-invariant (LTI) model of multichannel communications system. Calculations have been made on the basis of impulse responses (IR) of modeled reverberation-less auditorium. MLS correlation measurements in a real- life lecture room have been performed as well, for verification of the SRS quality.