Computer modelling of speech intelligibility in underground stations

• Main Author: Yang, Lening
• Published: London South Bank University 1997
• Subjects: 534; Acoustics & noise analysis
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245130

The aim of this study is to develop a ray tracing computer model for predicting speech intelligibility in underground stations. There are four parts to the study: correctly modelling the sound field in underground stations; developing a mathematical model for predicting speech intelligibility using a ray tracing computer model; using the model to investigate ways of improving speech intelligibility in underground stations; and using the model to analyze the sound field in long enclosures with multiple source systems. Four computer models have been developed for investigating acoustic parameters in different conditions or different types of space. The models have been validated with scale model measurements, and the predictions have also been compared with classical room acoustics. Three new contributions to the ray tracing computer model have been developed in this project: the reverberation time tail compensation, the exact representation of curved surfaces, and diffraction effects. A mathematical model for predicting speech transmission index in long enclosures using the ray tracing method has been developed. The model has been shown to be more accurate and efficient by comparison with scale model measurements and measurementsm ade in a real underground station. The model has been used to investigate ways of improving speech intelligibility in different noise levels and with different source spacing. Finally, the quasi-diffuse sound field theory for long enclosures with multiple source systems has been developed and justified as an approximation method for a quick investigation of speech intelligibility in underground stations.