Hi Randy,
Well, at times I've been led to believe that the heating/air
conditioning might be the source of the problem. But when I take a
closer look, there is no correlation at all. I live in a typical
suburban neighborhood, and I can definitely see a daily cycle of noise
that correlates with the traffic on a nearby busy street. But nothing I
can identify correlates with the occurrence and eventual subsidence of
the noise episodes.
I definitely do see seasonal variations that effect the need for
re-leveling the system. Especially in the spring and fall when the
ground freezes and thaws. I don't believe the water table is a
significant issue in my location.
I also can see a daily cycle in the leveling of the sensor. I have a
spare channel of my A/D converter connected to the leveling test point
on the circuit board. I display the voltage, updated at 30 second
intervals, on a readout in my data logger display. Gives me a way to
monitor the status of the system and get a heads up when the tilt is
starting to get out of the acceptable range. I record the voltage in a
"pseudo-PSN" file and can track the long term drift, on which is
superimposed a sort of daily sawtooth pattern that I take to be the
consequence of solar heating on the house or surrounding ground.
Interesting, but not related to my noise problem in any way that I can
fathom.
Larry
On 6/20/2012 11:19 AM, Randall Pratt wrote:
>
> Larry,
>
> Is there a vibration source that could alias to low freq? If the
> loose leveling screw increased the effect then maybe that indicates a
> location input.
>
> A second thought is your water table or frost level. In my case the
> ground water level comes up to or above my basement floor most spring
> seasons when the ground thaws. I seem to get increased transmission
> of traffic noise when the ground is saturated. When I operated my
> Lehman I had large tilts during freezing, thawing and ground water
> changes.
>
> Randy
>
Hi Randy,
Well, at times I've been led to believe that the heating/air
conditioning might be the source of the problem. But when I take a
closer look, there is no correlation at all. I live in a typical
suburban neighborhood, and I can definitely see a daily cycle of
noise that correlates with the traffic on a nearby busy street. But
nothing I can identify correlates with the occurrence and eventual
subsidence of the noise episodes.
I definitely do see seasonal variations that effect the need for
re-leveling the system. Especially in the spring and fall when the
ground freezes and thaws. I don't believe the water table is a
significant issue in my location.
I also can see a daily cycle in the leveling of the sensor. I have
a spare channel of my A/D converter connected to the leveling test
point on the circuit board. I display the voltage, updated at 30
second intervals, on a readout in my data logger display. Gives me
a way to monitor the status of the system and get a heads up when
the tilt is starting to get out of the acceptable range. I record
the voltage in a "pseudo-PSN" file and can track the long term
drift, on which is superimposed a sort of daily sawtooth pattern
that I take to be the consequence of solar heating on the house or
surrounding ground. Interesting, but not related to my noise
problem in any way that I can fathom.
Larry
On 6/20/2012 11:19 AM, Randall Pratt
wrote:
Larry,
Is there a vibration source that could
alias to low
freq? If the loose leveling screw increased the effect
then maybe that
indicates a location input.
A second thought is your water table or
frost level.
In my case the ground water level comes up to or above my
basement floor most
spring seasons when the ground thaws. I seem to get
increased transmission
of traffic noise when the ground is saturated. When I
operated my Lehman
I had large tilts during freezing, thawing and ground
water changes.
Randy