... You certainly haven t. The Hum is generally described between 30 and 80 Hz. You will record LF rumble such as you describe everywhere from many (includingMessage 1 of 16 , Jun 4, 2009View Source
> -----Original Message-----You certainly haven't. The Hum is generally described between 30 and 80 Hz.
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Behalf Of Joe Breskin
> Analyzing these recordings (in a neighborhood where several other
> houses are plagued by hum) I have found some low frequency components,
> most centered around 12Hz that appear to be composed of several
> asynchronous sources modulated at around 2-5Hz at around -56 dB but
> this system has not conclusively captured the "hum"
You will record LF rumble such as you describe everywhere from many
(including natural) sources, even out in the wilderness due.
FWIW the PMD671 has rather noisy mic preamps (I repair these in my day job).
But the level that people hear Hum is not subtle, so that shouldn't be a
>Search the archives for "Earthworks" and you will get the details of my
> Who else is currently actively trying to record the Hum and how are you
> doing it?
Also search the message archive here for aggregate rumble and you ll find links to my floor slab recording via a levitated piezo, and stereo comparisons toMessage 2 of 16 , Jun 4, 2009View SourceAlso search the message archive here for "aggregate rumble" and you'll
find links to my floor slab recording via a levitated piezo, and stereo
comparisons to two other recordings (the original of one - Surrey -
seems to have evaporated) and one of Moir's Auckland recordings.
I've spoken to our water utility engineering group about the well pumps
here in Cape Coral and visited two of them, one with an induction motor
drive and one with VFD. I listened to the downpipe on each with a
contact microphone (an electret) and found nothing that sounded like
what we seek. The induction drive spins up quickly to 180Hz and 540Hz
principal components while the VFD slowly spins up and settles at
~400Hz. All of the well pumps here (several dozen of them over a few
square miles) are set at about 750 feet depth and run irregularly as
dictated by demand and the control system's load distribution criteria.
These pumps were ruled out as my source, although they surely contribute
to the earth rumble I've repeatedly captured. The closest is about a
mile north of my location.
I've also investigated the sewage system here. There are lift stations
all over the city which are all induction drives. Each cycles as
required and typically runs for a minute per cycle. I can see harmonics
from one of them on a VLF loop (and also could on an E-Field whip before
switching to the loop) that I operate and stream continuously
(http://126.96.36.199/vlf9.m3u). These, also, sound nothing like The Hum.
Hi Tom, Looked extensively at your drawings, very interesting. Go for it, some substantive progress needs to be made on the issue. Your idea seems to be wellMessage 3 of 16 , Jun 4, 2009View SourceHi Tom,
Looked extensively at your drawings, very interesting. Go for it, some
substantive progress needs to be made on the issue. Your idea seems to
be well thought out.
My idea with the strain gauge and large metal disk would be to increase
the surface area of the device significantly more than a microphone
could offer, with the hope that the additional area would move the disk
sufficiently to produce a reasonable and replicable output from the
strain gauge. Also, the idea of examining the effect that the HUM may
have on the disk by using an oscilloscope may allow an interpretation
not simply based on audibility.
It's just a thought. I am going to contact my aspiring inventor friend
and try to pique his interest.
Oddly enough, the HUM seems to have disappeared from my area, my wife
heard it a little in the country last weekend, but in the city, silence.
--- In email@example.com, Tom Becker <gtbecker@...> wrote:
> > ... the use of a fairly large metal diaphragm with a strain gauge
> centered on the plate may show the effects of the HUM, rather than
> conventional microphone technologies...
> Perhaps, but that sounds like a large conventional microphone, I
> Jim. Most mics have a diaphragm with a magnetic (a dynamic mic) or
> electric (capacitive or piezo) motion sensor, usually centered on the
> The thing I'm tinkering with is a microphone variant, a pair of
> piezo-coated copper disks that are magnetically levitated - in an
> attempt to measure gravity modulation or noise. It makes a great
> seismometer when the disks are summed in phase; out of phase, they
> cancel except for the different motions imparted on two differing
> that they support. This is a small device, but very sensitive.
> http://rightime.com/Hum/Gravity/Floater3.bmp A simple one looks like
> this: http://rightime.com/Hum/Gravity/DSCN5317a.JPG