Laboratory experiments for speech intelligibility and speech privacy in passenger cars of high speed trains

Abstract

This study explores the speech privacy criteria in passenger cars of high-speed trains. In-situ measurements were performed in running trains to analyze the acoustical characteristics of interior noises in train cabins, and laboratory experiments were conducted to determine the most appropriate single-number quantity for the assessment of speech privacy. In the listening tests, the participants were asked to rate (1) speech intelligibility, (2) speech privacy, and (3) annoyance with varying background noises and signal to noise ratio (SNR). From the results of the listening tests, the effects of background noise levels and SNR on the speech privacy and annoyance were examined and the optimum STI and background noise levels in the passenger car concerning both speech privacy and annoyance were derived.