I have previously written on the subject of the phenomena of low resonance noise which can intrude into our lives and cause annoyance, discomfort and even drive some particularly sensitised individuals to the brink of madness. My In-Laws have been so afflicted and with no resolution to their problem in the offing.
It may not be possible to trace the source of a particular mysterious noise because not everyone can actually hear it.
What can be done?
In most cases it is just a matter of becoming acclimatised to the sound and like those living next to a busy rail route or under a commercial jet flight path the regularity and familiarity of it may reduce its intrusion.
In many incidences of the noise it is not entirely clear if the resonance is generated by mechanical or human activities.
What about if the source is in nature?
Houseboat residents in California, United States first heard a mysterious noise some years ago .
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 through the summer months. Those in the Marina location did not at first think much about it. There were many competing natural sounds in the environment from crickets to birds, dogs to cats and so on.
However, the eerie sound persisted and those new to the intrusion, after comparing notes with longer serving moored residents some 500 in total , came to realise that others had been tormented in such a way for many years.
Some houseboat occupiers described the noise as similar to the buzzing of an electric razor--but magnified 10 times louder. Others said it sounded like an Air Force bomber or a neighbour using a powerful generator. One houseboat owner said the eerie humming was tuned to the middle C key on her piano.
These were specific descriptions of the the mysterious sound, but no had been able to uncover the hum's source or why it seemed to be heard only at night and during the summer.
Populist theories on the source of the hum included an obscure sewer pump or even a secret military device.
Marine Scientists from the Steinhart Aquarium in San Francisco suggested that the hum may be traced to the mating activities of fish in the waters beneath the houseboats.A particularly baffling aspect of the hum was the fact that the hulls and superstructures of some houseboats were able to conduct the noise, while others did not. In one instance it was only when a resident added a bedroom to his houseboat and floated it on several large metal pontoon spheres that the hum became evident where before it had not been heard.
The more pleasant aspects of Marina living began to be affected by the persistent noise and residents had to resort to investing in a wide array of earplugs" or by using a white-noise machine that provided a more soothing sound to drown out the annoying buzz.
The level of the complaint became very real and County Health Officials enlisted the aid of sound engineers to investigate the hum. The research initially only added to the mystery.
The specialists paddled around the bay in a small rowing boat several times, tracked the hum and recorded its frequency with special listening devices dropped into the water. Several "hot spots" where the sound appeared strongest were plotted but otherwise it proved transient and unpredictable in its intensity.
One important conclusion was that the frequency of the hum was not consistent with that of typical frequencies made by standard mechanical or electrical equipment.
By deduction there could only be one real source- that of "singing fish".
One suspect, a fist-sized fish, called the plainfin midshipman was common to the shallow waters and mud flat environment of California.
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. This "sexed up" fish theory produced scepticism and humour amongst some houseboat residents, who continued to cast doubt that the hum could be produced by anything biological because it was so constant and still sounded more like the buzzing of machinery.
In a bid to support their lovesick fish theory Marine Researchers resorted to trawling in the bay and collected several of the toad-like plainfin to bring back to tanks at the aquarium for study.
After the midshipman fish had settled into their new controlled environment, acoustic engineers were able to match up the sound of the fish to an archive recording of the same species from 1977 thereby proving beyond reasonable doubt that the source had been found.
This revelation, you may think, would give a degree of closure to the afflicted houseboat dwellers but there was little that could actually be done to attenuate the sound of the amorous fish.
It will certainly have crossed the minds of those hard pressed and exhausted residents to adopt the unthinkable, drastic and wholly unrealistic measure of eradicating the entire population of the midshipman from the local environment.
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