SEATTLE - Normal conversation ranges between 60 and 70 decibels.
When trying to talk to neighbors of the ship canal bridge in Seattle, conversation is hard because the decibel from traffic in the express lanes is about 85 decibels.
Now, the Washington State Department of Transportation is trying to fix it with sound-deadening curtains.
There is no dispute about the nearly half-century of loudness coming from traffic on the bridge. And this is not the first time that WSDOT has tried to fix it. But this may be the first real chance to knock the noise level below 67 decibels, which is the target threshold WSDOT has set for itself.
The heavy plastic and fabric curtain about four feet by eight feet in size. WSDOT says if they have enough of them, they should be able to knock about 20 decibels off and transform the neighborhoods that surround the bridge.
Why is the ship canal bridge a bigger noise maker than others? WSDOT says it's because of its double deck design. Most of the noise on the upper deck goes up. But on the lower deck express lanes, it bounces off the upper deck and down and away from the bridge into the places where people live and work.
Lorena Eng, the administrator for WSDOT's Northwest region says the neighborhoods "were here first" before the bridge was built with the expansion of the interstate highway system.
So why not just put up a concrete sound wall like WSDOT has been doing along I-5 and I-405 for years now? The issue is determining how much weight the bridge can safely tolerate. Even the weight of the heavy curtains to be hung in layers paralleling traffic lanes could even be a factor. It could restrict how many curtains the bridge could handle.
All this is a test of a $7 million dollar project. The work begins on Wednesday for the first section along the south end off the bridge.