National Traffic Safety and Environment Lavoratory

Traffic Noise Reduction


This fiscal year, we began working on the development of technology to contribute to further reductions to tire-road noise. The technology consists of a sound absorption system using the tire-wheel-in method that is able to be implemented independent of both road surface pavement measures and improvements to tire grooves and structure. In connection with the development of the tire-road noise prevention, we are conducting research on the aging of vehicle noise measurement tracks, on the sound intensity measurement method of transient noise, and on the methods to identify noisy vehicles and evaluate of the level of annoyance caused by the increase in the number of noisy vehicles fitted with modified mufflers. With regard to railway noise, we are conducting research in areas such as the effect of Noise barrier walls in order to improve the accuracy of railway noise estimates. We are also working to evaluate and study noise created by new railway traffic systems such as light rail systems.

Current Major Research Topics

  1. Research on techniques to prevent tire-road noise by optimizing noise absorption characteristics of car bodies
  2. Research on aging of ISO test track surfaces
  3. Research on sound intensity based analysis methods of sound radiation characteristics emitted from transient noise sources
  4. Research on methods for identifying noisy vehicles and evaluating the annoyance caused while driving
  5. Research on improving the accuracy of estimates on the effect of Noise barrier railway noise estimation methods

Past Major Research Topics, etc.

  1. Research on bench test and evaluation methods for automobile tire-road noise, and techniques for reducing this noise
  2. Research on testing methods for evaluating noise produced by tires when driving
  3. Surveys of vehicles fitted with replaceable mufflers and surveys of the impact of noise
  4. Research on the optimal placement of microphones for searching for mobile noise sources
  5. Research on improving accuracy of noise forcast methods for local railways
  6. Fundamental research on methods for reducing noise generated by pressure waves transmitted along tubes

Major Testing Facilities and Devices

  • Vehicle-mounted tire-road noise testing device
  • Multipoint noise analysis device for use in anechoic chambers
  • Vehicle-mounted ANC control device
  • Standard noise emitter for anechoic and reverberation chambers
  • Microphone motion device
  • Microphone impedance meter
  • Road surface irregularity meter
  • Sound shielded duct simulation device
  • Flat tire detection system for train operation