Many people have heard and been puzzled by this type of phenomenon, John. A=
bout 10 years ago, while leading a soundscape trip to SE Alaska, a group of=
us was standing on the northern shore of Chichagoff Island one evening whe=
n, suddenly, there occurred a sonic event that was completely baffling. It =
was a very intense and low frequency sound that literally shook us physical=
ly, meaning that it was more felt than heard (since it was mostly infrasoni=
c). We were at least a dozen miles distant from any human electro-mechanica=
l source and there were no boats or marine mammals anywhere within sight. B=
ut most of us instinctively felt that this was not biological in origin. Mo=
re likely it was geophonic (earth-generated, somehow). It didn't last long =
enough for us to recover from the impact of the physical sensation and for =
me to grab my equipment to try to record it. But there were seven of us who=
had no doubt about its presence.
Bernie Krause
On Jan 22, 2013, at 8:31 AM, John Crockett <> wrote:
> Greetings
>
> I mostly record around our property in southern Vermont, except when
> I go to the Bay of Fundy in August. I have noticed for some time that =
> there is a constant low frequency noise in all of my recordings. I
> never investigated it until last night when I woke up and could hear
> a loud hum at around 90 Hz. That turns out to probably be low
> frequency tinnitus because it is not present in the test recordings I =
> made in the night, while I could "hear" it plainly. But in the
> process of investigating that hum I was reminded of this other noise
> because it is so prominent in the spectra.
>
> I made multiple recordings in various rooms of the house and the
> cellar and porch today, and outside pointing the microphone in four
> directions. The noise is there in all recordings, loudest outside,
> quietest in the cellar.
>
> The frequency is low, around 45 Hz with clear harmonics. The
> intensity is low, around 5 dB SPL inside and about 15 dB SPL outside. =
> Those numbers are very, very approximate. I do not have a SPL meter
> that reads that low, so I extrapolated based on the levels in the wav =
> file. Also, in order to hear it at all and have the harmonics show up =
> in a spectrum image, I had to apply a High Cut filter above 100Hz.
> Otherwise it is buried in mic noise and whatever else.
>
> It's not a problem, I'm just curious what it is in the environment
> that is producing this sound. Is this normal background noise? We
> live in a small valley between two modest ridges. The sound seems to
> be louder by a few dB when the microphone is pointing south, down the =
> valley. I wonder if it is an acoustic feature of the valley. My next
> experiment will be to get out of this valley and see if I still
> record this rumble.
>
> Any thoughts?
>
> John
>
> John Crockett
>
>
> Let us live in harmony with Earth
> And all creatures
> That our lives may be a blessing
>
>
>
>
>
>
> ------------------------------------
>
> "While a picture is worth a thousand words, a
> sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
>
> Yahoo! Groups Links
>
>
>
>
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