Struggle to stop 520 Bridge ‘kerplunk' sound continues in Medina

MEDINA, Wash. — Neighbors concerned about the noise from vehicles on the new SR 520 bridge are learning what the state might be able to do to mitigate the issue.

On Friday afternoon, researchers from the University of Washington presented preliminary results of a study into the noise to the Medina City Council.

Since the bridge’s opening, neighbors have complained about the “kerplunk” sound they hear every time a car drives over an expansion joint.

The Washington State Department of Transportation had previously pointed to a 2016 study that found the new bridge is quieter than the old bridge – and the perception of increased noise is due to quieter pavement in relation to the expansion joint noise.

So far the newest study has found the noise is loudest above the expansion joints, at night, with skinnier tires causing more noise than wider tires. However, WSDOT says the noise levels are still well under federal levels that would require mitigation.

UW researchers recommend a controlled laboratory study into how speed affects the noise and potential ways to reduce the noise, including using “sinus plates” or filling the gaps between the center beam with foam.

The study is on-going with the final report expected in 2019.

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