>> John Neville said he'd heard the humming, and the quote of the Nature
>> abstract says
>>
>>> free oscillation peaks have been consistently identified in seismic
>>> records in the frequency range 2-7 mHz
>>
>> Either there's a typo or John needs a rather high sample rate to
>> record that hum...
>
> Hi, Dan,
>
> The way I read this is 500 seconds/cycle to 143 seconds per cycle.
> The lower-case "m" refers to milli or 1/1000 of a Hz or 1000 seconds
> per cycle.
>
> Does that make sense in context? Is this why it took seven years of
> analysis?
>
> Upper-case "M" refers to mega or 1,000,000 Hz.
Thanks, Richard, that clears it up for me. But John Neville isn't
hearing the infrasonic "hum," either. John, have you ever been in an
anechoic chamber and heard the internal sounds you perceive when
there's no external stimulation?
Then there's the possibility of something like a gas well compressor a
couple of miles away, too.
The best "nothing" I think I've ever recorded was in July, an
overnight (with permit) session in Yosemite's Mariposa Grove. I was
ready for a sweet dawn chorus when some kind of highway or pipeline
construction started up at 4:00 AM some miles away. Not audible with
ears, but amplified it replaced the superb natural quiet.
-Dan Dugan
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