Re: HUM_FORUM: Re: New member questions, again
> ... piezo accelerometers...
Eleanor, the accelerometers are actually capacitive devices, similar to many modern MEMS sensors. This is one, an Analog Devices ADXL203 that can resolve 0.001g at 60Hz, which is what I'll use for a few experiments. FYI: http://www.analog.com/en/prod/0%2C2877%2CADXL203%2C00.html
Your hinged-beam-on-piezo sure sounds like a turntable tonearm with less mass. In fact, a magnetic phono cartridge might do as well as a piezo, and a piezo sounder might do a better job than a quartz RF crystal (which is what, I think, you described). Nevertheless, I no longer have a turntable - and, I imagine, tonearm cartridges cost a mint today - but I do have a small pile of piezo disks with which I can play with your idea.
> ... gravity waves, or gravitational waves?
Neither; I proposed modulation.
I have been thoroughly chastised for my mention of gravity; one previously-dominant member left this group because of the cavalier mention of it. He did not read the words "gravity waves" from me but inferred them, nonetheless, and couldn't continue - so blasphemous, apparently, must be the notion.
I am an engineer of several disciplines but I am not a physicist, so I cannot enter into a technically accurate discussion about gravity except to the extent that I understand that "down" is in the direction of the local gravity vector, which points toward the apparent center of mass of the earth beneath it. Objects fall toward it.
I suggested that gravity might be modulated - that it's force might change with time. It seems rational to me that a change in local gravity intensity and direction might result from movement of the mass density beneath it, perhaps in the magma. That should generate waves only if gravity exhibits velocity, but that is beyond my conjecture.
Most seem to view gravity as an unerringly constant force; I question that. I suggested only that a suspended mass might deflect a magnetic spring differently if the force of gravity changes, and attempted to detect that at audio rates. I built a simple vertical magnetically-suspended-mass sensor, using differential piezo disks that supported the magnetic gap and, thus, the mass. A recording produced by that device is here: http://rightime.com/Hum/Gravity/CapeCoral20080525Below100Hz.mp3 I do not propose that this is a recording of The Hum, calling it "aggregate rumble", whatever the source.
On the chronology of the sensation, others here have quoted quite old apparent observations.
I'd like to hear your comments.