A novel method for measuring highway barrier or retaining wall sound reflections in situ

摘要

Large retaining walls and sound barriers have the potential to reflect traffic noise towardsrnnearby neighborhoods and by doing so may increase imission sound levels there. In arnrecent project it became necessary to determine the sound-reflective properties of such arnwall before and after the installation of sound-absorbing material in order to assess thernperformance of the absorbing material. More conventional methods, such as impedancerntube testing and impulse testing using a yachting cannon, were deemed undesirable becausernof small area coverage and the potential for startling drivers, respectively. The impulsernresponse of reflections off the wall can be determined using a steady-state filteredrnmaximum length sequence (MLS) signal. Synchronous averaging of numerous impulsernresponses causes moving traffic to "vanish" in the long-term in a manner similar to timelapsernphotographs. Results have been shown to be comparable to impedance tube tests.rnThe method is conceptually robust and straightforward, but can be affected by variousrnfactors that require careful consideration.