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Project Experience: U.S. Route 101 Noise Monitoring, California

The Challenge

The California DOT (Caltrans) needed a study of traffic noise exposure and the effects of reflections from noise barriers.

The Strategy

HMMH conducted the study in close coordination with community groups. We provided extended long-term monitoring and detailed reporting of existing traffic noise levels at many locations within the community. The ongoing program involves short-term noise monitoring before, during, and after a roadway-widening program, which includes:

  • Replacing a noise barrier
  • Applying sound-absorbing materials to the barriers
  • Resurfacing the road with open-graded asphalt to reduce noise emissions
An article on the barrier sound-absorbing materials was recently published in the Marin Independent Journal, titled, Soundwall pays off: Residents along Highway 101 say noise has been reduced. An excerpt follows:
quote Patrick Murphy of San Rafael likes what he doesn't hear. Crews are finishing the installation of thousands of sound-absorbing panels as part of a $3 million retrofit of the existing Highway 101 soundwall to give area neighbors relief from freeway noise. quote