PSN-L Email List Message

Subject: Fw: geophone for urban search work
From: "Larry Cochrane" cochrane@..............
Date: Thu, 16 Aug 2001 20:55:06 -0700


From John Lahr. -Larry

----- Original Message -----
From: "The Lahrs" 
To: ; 
Sent: Thursday, August 16, 2001 8:33 PM
Subject: Re: geophone for urban search work


> (Larry, could you forward this to the PSN?  Thanks!)
>
> Hi Rick,
>
> I don't think a 1 Hz geophone would be the best tool to pick up a tapping
> noise.
> You might want to use a less expensive 4.5 or 8 Hz geophone or even a
> microphone.  In 1992 I used microphones to locate neighborhood gunshots.
> The recording system digitized the signals at 2,000 samples per second.
> A high sampling rate would also be required for a your search and rescue
> system, both to record the high frequencies and to allow very accurate
> timing for locating the source with three sensors.
>
> There is information on the gunshot system here:
> 
>
> Cheers,
> John
> At 02:29 PM 8/12/2001 , you wrote:
> >Rick,
> >
> >I'm not sure if a geophone would be good for this type of thing,
> >maybe....I'm CCing the PSN mailing list. Maybe someone on the list has
some
> >ideas for you.
> >
> >PSN'ers, please CC Rick at seadog@....... since he is not on the list.
> >
> >-Larry Cochrane
> >Redwood City, PSN
> >
> >
> >----- Original Message -----
> >From: "Rick Howard" 
> >To: 
> >Sent: Sunday, August 12, 2001 12:43 AM
> >Subject: geophone for urban search work
> >
> >
> > > Larry,
> > >
> > > Please advise whether you feel a geophone like the Mark
> > > Products L10B you have for sale might prove useful as
> > > a device to detect a person tapping on a collapsed structure
> > > when buried under rubble.
> > >
> > > I'm a Technical Search Specialist for one of the FEMA
> > > Urban Search & Rescue Task Forces, and we use a
> > > sophisticated device (http://www.delsar.com) as a person
> > > locator, but this equipment is expensive and limited as
> > > far as access for training.  How might a geophone work as
> > > as a detector if someone was tapping on a structure (pipe,
> > > concrete, etc) 20-100 feet away?  The general frequency
> > > range the Delsar unit calls for is 1-3000 Hz.  I'd love
> > > to buy a geophone to experiment with.  I can solder circuits
> > > pretty well, if you can recommend a circuit to go with it.
> > >
> > > Any advice would be appreciated.  I serve in search and
> > > rescue as a volunteer; you'll incur no liability in
> > > giving me your recommendation - I'm just looking to
> > > experiment with other available, cheaper tools in a
> > > quest to do my search job better.
> > >
> > > Thanks -
> > >
> > > Rick Howard
> > > Tech Search Specialist
> > > California Task Force 3, Menlo Park


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Larry Cochrane <cochrane@..............>