Re: Relationship Between Velocity, Phase and Frequency
- From: Robert Baer <robertbaer@xxxxxxxxxxxx>
- Date: Thu, 27 Nov 2008 21:19:46 -0800
nomi wrote:
Dear all,There is no specific relationship.
I am currently here to monitor the seismic activity in Pakistan, I
have a problem,I want to know what is relationship between particle
velocity, Phase and frequency in case of vibrosies
2. there is main power line passing over seimic lines and we are
failed to get any fruit full information in all chennels after this
seismic line, even at distance more than two Km, power line noise is
dominent,
If u gays have any sugession, please send me,
Phase can be measured or considered as a time difference of one (sine) wave WRT another at the same frequency; one complete cycle being 360 degrees and a time shift making one waveform "start" (or "end") when the other is at a peak is 90 degrees (or 270 degrees) delayed or advanced (or shifted, depending on terminology one is most familiar using).
Particle velocity i would think is dependent on the medium and the kinetic elasticity, where the energy supplied by a given disturbance (say sonic shock wave) may be more closely modelled to particle velocity and intensity, and the frequency (assuming sine wave) may be secondary.
I am an electron pusher, not a rock pusher so that part is a bit outside my expertise.
Obviously, even if the above answers some questions posed, it is useless in solving the implied problem.
Now, there may be ways to tackle power line noise interference.
One could use sharp (narrow bandwidth) analog filters tuned to fundamental, third, fifth, and seventh harmonics of the line frequency.
That can be rather sucessful in reducing the noise, but can time-distort and waveform distort electrical analogs of shock waves that i presume you are trying to analyze.
A second approach is to digitize the incoming waveforms, perform a Fourier Transform, pick out (ie remove) the line frequency harmonics, and then do an inverse Fourier Transform; I believe that this could be done in real time with little trade-offs.
A third approach is a bit nastier; requires repetitive shocks of the same type at intervals NOT correlated to the powerline frequency(ies), sampling and "building up" a count of each timeslot measured from time zero (when the shock is applied).
Since the desired signal is not correlated, everything else is noise and does not add up as fast as desirable signal.
This approach is a slight variant of pulse height analysis used in determinimg nuclear radiation specie.
A fourth approach is to try shielding the powerline junk from the detecting equipment, which might require a combination of a modified Faraday cage and high permability sheeting.
Depending how severe the interference is, one may need to combine the fourth approach with one of the others.
.
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