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#1
Posted to rec.audio.pro
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Earthquake recordings?
Just curious if anyone happened to be recording a take as the quake hit. It
would be interesting to look for infrasonic signals in the audio - if there was no high-pass filter being used. Sean |
#2
Posted to rec.audio.pro
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Earthquake recordings?
"Sean Conolly" wrote in message ... Just curious if anyone happened to be recording a take as the quake hit. It would be interesting to look for infrasonic signals in the audio - if there was no high-pass filter being used. *All* professional microphones have a built-in high pass filter. For cardioids and bipolar microphones, the back side of the diaphragm is necessarily exposed to the atmosphere. For omnis, there has to be a vent or the diaphragm would be damaged if you changed its elevation too much. If you want to see the true infrasonic signals in a quake hit, you want a siesmograph, but even they have high pass filters, just ones tuned to far lower frequencies. Ground distance measurements by a GPS lack the high pass filter, but their high frequency response is relatively poor. |
#3
Posted to rec.audio.pro
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Earthquake recordings?
Arny Krueger wrote:
"Sean Conolly" wrote in message ... Just curious if anyone happened to be recording a take as the quake hit. It would be interesting to look for infrasonic signals in the audio - if there was no high-pass filter being used. *All* professional microphones have a built-in high pass filter. For cardioids and bipolar microphones, the back side of the diaphragm is necessarily exposed to the atmosphere. For omnis, there has to be a vent or the diaphragm would be damaged if you changed its elevation too much. If you want to see the true infrasonic signals in a quake hit, you want a siesmograph, but even they have high pass filters, just ones tuned to far lower frequencies. Ground distance measurements by a GPS lack the high pass filter, but their high frequency response is relatively poor. I have used B&K lab mikes for classical recording and they have some very interesting issues that result from the very good low frequency response. Once had a run-through that was great but then as soon as they lit all the candles in the hall, the air currents started pegging the meters.... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#4
Posted to rec.audio.pro
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Earthquake recordings?
"Scott Dorsey" wrote in message ... Arny Krueger wrote: "Sean Conolly" wrote in message ... Just curious if anyone happened to be recording a take as the quake hit. It would be interesting to look for infrasonic signals in the audio - if there was no high-pass filter being used. *All* professional microphones have a built-in high pass filter. For cardioids and bipolar microphones, the back side of the diaphragm is necessarily exposed to the atmosphere. For omnis, there has to be a vent or the diaphragm would be damaged if you changed its elevation too much. If you want to see the true infrasonic signals in a quake hit, you want a siesmograph, but even they have high pass filters, just ones tuned to far lower frequencies. Ground distance measurements by a GPS lack the high pass filter, but their high frequency response is relatively poor. I have used B&K lab mikes for classical recording and they have some very interesting issues that result from the very good low frequency response. Once had a run-through that was great but then as soon as they lit all the candles in the hall, the air currents started pegging the meters.... Classic case of being careful about what you wish for, as there may be unintended consequences once you get what you wish for. B&K apparently invest quite a bit in the venting system that they use to obtain that kind of LF response. I hear tell of porous ceramic plugs and the like. |
#5
Posted to rec.audio.pro
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Earthquake recordings?
"Sean Conolly" wrote:
Just curious if anyone happened to be recording a take as the quake hit. It would be interesting to look for infrasonic signals in the audio - if there was no high-pass filter being used. Sean I was surprised how smooth it was and something just over 1 Hz. Some light rattling in my kitchen. Greg |
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