Experimental Comparison Between Direct and Indirect Measurement Methods for Speech Transmission Index

Abstract:

The speech transmission index (STI) and speech transmission index for public address system (STIPA) metrics at 12 receivers in 4 rooms, with a total of 48 acoustic conditions, were measured using the direct and indirect method and the measurement results of the two methods were compared, with a particular attention on the influence from the frequency response of the measurement system. The results show that, there is no substantial difference between STI and STIPA metrics; both direct and indirect measurement can be used as an objective rating method for speech intelligibility, as long as the standardised measurement program and measurement system are adopted.