When measuring the Speech Transmission Index (STI), until now one had to choose between two alternatives: impulse-response based full STI measurements (indirect method), or measurements based on modulated STIPA signals (direct method). Limitations apply when using either method. A novel procedure is proposed to measure the full STI through the direct method. The procedure combines advantages of indirect full STI measurements and direct STIPA measurements, completing a full STI measurement in 65.52 seconds. Similar to STIPA, the test signal is simultaneously modulated with 2 modulation frequencies per octave band. However, a rotation scheme is applied that uses a different set of modulation frequencies during different stages of the measurement, ending up with a full matrix (7 octaves x 14 modulation frequencies).
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