Hummer a Bummer : Mysterious Buzz Torments Sleepless Houseboat Owners, Confounds Scientists

Donna Michel first heard the mysterious sound last year as she was drifting off to sleep in a lower-level bedroom of her houseboat. The eerie humming “clicked on” in the early evening, peaked in volume around midnight, and finally went away in the morning--a pattern that would be repeated all summer.

“At first I thought it was a transitory type of thing,” Michel said one recent afternoon. “Then when it didn’t go away, my husband and I started to ask ourselves: ‘Are we going crazy?’ ”

After talking with neighbors, Michel found out otherwise. The hum, Michel learned, had been tormenting her neighbors for years and was well-known among residents of Marin County’s houseboat community--about 500 homes that float in the shallow waters of Richardson Bay just north of San Francisco.

Some houseboat residents describe the noise as similar to the buzzing of an electric razor--only 10 times louder. Others say it sounds like an Air Force bomber or a neighbor using a powerful generator. One houseboat owner said the eerie humming is tuned to the middle C key on her piano.

Unknown Source

But while residents are specific when it comes to describing the mysterious sound, no one has yet discovered the hum’s source or why it seems to be heard only at night and during the summer.

Theories on the source of the hum abound, however. Suggestions have ranged from an obscure sewer pump to a secret military device, but none have been confirmed. This week, officials at the Steinhart Aquarium in San Francisco suggested that the hum may be traced to the mating activities of fish in the bay.

Among the baffling aspects of the hum is the fact that some houseboats conduct the noise, while others do not. Peculiar also is that some houseboats carry the hum some of the time and are otherwise silent.

For example, Tom Watson, president of the Marin County Floating Homes Assn., did not hear the noise until he added a bedroom to his houseboat and floated it on several large metal spheres. The added bedroom proved to be a good conductor for the hum.

“It was so loud it gave me a headache,” Watson said recently, adding that he had to cover his head with pillows in order to sleep. The noise then disappeared for a “good two-year lull” Watson said, before returning.

Lots of Earplugs

Michel said she has overcome the hum by “investing in a wide array of earplugs” and by using a white-noise machine that provides a more soothing sound to drown out the annoying buzz.

“Grim resignation sets in. . . . Now that we know what to expect, we have learned how to live with it,” she said.

Residents here are clearly willing to tolerate the inconvenience in order to enjoy the more pleasant features of marina living.

Assortment of Boat Styles

Houseboats have been moored in Richardson Bay for more than a century. Floating homes here vary in price and style, from ragged-looking barges with makeshift coverings to the more stylishly designed $1-million wood-frame homes with picture windows.

Most houseboat owners pay up to $500 a month to lease a berth that allows them to tether their homes to wooden docks and connect to utility lines from shore. Others simply drop anchor in the bay, but county officials have ordered these so-called “anchor-outs” to leave the bay within the next two years.

Nestled among the Marin County hills, Sausalito and the Tiburon peninsula, houseboat owners are afforded spectacular vistas of San Francisco Bay and easy access to aquatic recreation.

Sound Engineers Baffled

Baffled Marin County health officials have enlisted the aid of sound engineers from Frank Hubach & Associates of Berkeley to investigate the hum. The research has only added to the mystery.

Stephen Neal, a Hubach engineer, has paddled around the bay in a small rowboat several times, tracking the hum and recording its frequency with special listening devices dropped into the water.

Neal located several “hot spots”--areas where the sound appeared strongest--but further investigation turned up nothing.

“The sound appears to come from nowhere and get louder and louder,” Neal said.

A report by Hubach & Associates did conclude that the frequency of the hum is not consistent with that of typical frequencies made by standard mechanical or electrical equipment.

Having ruled out standard machinery as the cause of the hum, engineers and health officials are now testing the noisy fish theory.

‘Singing Fish’

The suspected fist-sized fish, officially called the plainfin midshipman but also known as the “singing fish,” apparently favors the shallow waters and mud flat environment of Richardson Bay.

The modus operandi of the plainfin seems to provide a possible link to the hum. According to marine biologists, male plainfin collect in the bay during the summer, burrow into the mud and then vibrate their bladders in a seasonal mating call.

But the fish theory has produced skepticism and chuckles among some houseboat residents, who doubt the hum could be produced by anything biological because it is so constant and sounds like the buzzing of machinery.

Nonetheless, researchers from San Francisco’s Steinhart Aquarium went trawling in the bay Tuesday and collected several plainfin to bring back to tanks at the aquarium for study.

After the toad-like fish are given time to settle into their new environment, sound engineers will record the sound of the fish and compare it with charts of the Marin County hum. If it matches, sound engineers are confident they will have solved the longstanding mystery of the hum.

But even if the singing fish are found to be the answer, there is little that can be done to silence them or to remove the entire population from the bay.

“Residents there will just have to chalk it up to one of the charms of living on the bay,” said aquarium assistant curator John Hewitt.