Psychoacoustic Evaluation of Noises Generated by Passenger Seats for High Speed Trains

Abstract

Passenger acoustic perception is one of the main factors in order to evaluate the comfort in a High Speed Train (HST). While current measurement standards for interior noise (ISO 3381) only take into account objective measurements, some aspects of the soundscape inside a high speed train are not considered. Noise produced by the vibration of different interior assemblies, like squeak and rattle, are evaluated subjectively during commissioning tests. The first topic treated by this study is the development of a methodology for the specification of squeak and rattle (SR) noise produced by passenger seats. A correlation between a subjective assessment of rattle noise and psychoacoustic parameters is done. The novelty of this study is to take into account these anomalies as a part of the correlation and to find a method to allocate targets to seat suppliers during project development to reduce costs by avoiding expensive retrofit works. Another aspect related to the acoustic perception of a product is the sound quality associated to its functioning. Interior components are normally static components where a specific noise signature is not expected, but a passenger seat can have a dynamic operation by the passengers which could influence the perceived quality of the final product. Perceived quality is often used to target designs for different type of users and applications. It is applied widely in the automotive industry but no references exist for a rolling stock application. A methodology has been applied to assess the sound quality of passenger seats for typical operating noises of a seat like reclining, armrest, footrest, seat tray, etc. This part of the study allows the establishment of psychoacoustic targets for those operations in order to achieve a desired level of perceived quality. The methodology that has been used for both topics is based on jury tests of different acoustic recordings, using a statistically significant sample of participants of different ages and social positions. During this survey, people were asked to evaluate the acoustic comfort of the interior soundscape of high speed trains, and to evaluate also the robustness, quality and annoyance of some devices linked to the train seats. The subjects rated the response on a scale with several categories according to certain criteria. In summary, two methodologies are proposed: one for the specification of squeak and rattle noises related to high speed train operation and another one for the perceived sound quality of passenger seat operation.