SEATTLE (AP) — No one knows for sure what caused a humming noise that annoyed residents of the west Seattle neighborhood on Puget Sound, but one theory is the buzz was a fish mating call.

Noise abatement inspectors from the city’s Department of Planning and Development have been looking into the complaints, said the department’s Moon Callison. But, reports have been coming from such a wide area they have not been able to pinpoint the source.

The source could come from the water, which surrounds west Seattle on three sides. The sound? It could be the romantic habits of male Midshipman fish, calling females to their nests.

Or the hum could come from a cement plant, idling trucks or trains, ventilation fans, air compressors, the engines of ferries crossing Puget Sound or street sweepers in empty parking lots. These are all causes residents considered as they lay awake listening to the low frequency drone over the Labor Day weekend and posted comments on the West Seattle Blog. No one could track down the source.

The blog’s Patrick Sand said the sound was active for two or three days but stopped after people wrote about it. “That seems to have scared off the noise,” he said.

The hum has recurred over a number of years, he said. In the spring, it’s heard on the Puget Sound side of west Seattle, and in the late summer it’s heard by residents closer to the Duwamish River, Sand said, although he’s never heard it himself. “It comes and goes.”

A KING-TV report Thursday suggested it could be the mating call of the Midshipman fish amplified by reverberations from ships in the Duwamish River.

That’s not too farfetched, although it’s hard to imagine there would be enough energy generated under water to make a metal hull resonate with sound over a wide area on land, said Joseph Sisneros, an associate professor in psychology from the University of Washington who studies animal behavior.

“It would take a lot of fish to do that,” he said.

Sisneros was out until 11:30 p.m. Thursday dipping a hydrophone into Puget Sound, Elliott Bay and the Duwamish River, listening for Midshipmen fish looking for love. He heard no calling fish.

He did record a low frequency sound outside a cement plant, but it didn’t carry very far.

“I hate to be inconclusive, but we didn’t really find out one way or the other what the sound is,” he said Friday. “It’s an interesting mystery that’s for sure.”

Sisneros studies the Midshipman fish and says they were documented as the source of low humming heard by residents of houseboats in the 1980s in Sausalito, Calif.

The foot-long fish with a toad-like face ranges from California to Alaska waters, and they are common in Puget Sound, he said. It’s a deep-water fish most of the year, except for late spring and summer when they make nests in rocky shallow waters for egg laying.

“These fish sing like birds at night to attract females,” Sisneros said.

The sound is generated from the swim bladder that most fish have to control buoyancy. Midshipmen fish contract a muscle attached to the bladder to make their music.

“It’s like squeezing a balloon,” he said. “When females hear this it’s like an advertisement and the males bring them in to spawn.”

(© Copyright 2012 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)


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