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Re: Infrasound recorder

Subject: Re: Infrasound recorder
From: "Mike Rooke" picnet2
Date: Wed Feb 10, 2010 1:30 pm ((PST))
Depends if you wish to make your own sensor, or go with a scientific instrument 
with a known calibration to compare with other papers on the same subject?

The actual observable point where both channels on the Zoom H2 merge to DC is 
around 0.06Hz (16384 FFT Square windowing, sample rate 46.875 Hz (48000 Hz 
Decimated by 1024)

>From Memory the Korg MR1 is good to DC but I'd not recommend it for field use. 
>(short battery life and quite fragile)

Edirol R09HR I can test if needed, tends to have a bass lift where as the 
Olympus LS10 the opposite, I'd not recommended it due to its low frequency roll 
off / crud in the lows - that said Ive not tested the LS10's. - Sony D50 not 
sure never looked that low.

This (old) blog entry shows a large polymer electret:-
http://www.urlme.net/blog/?p=528

PVDF and Piezo Bender disks if cut to around 4nF capacitance are more sensitive 
than the EMFIT film - however since it can be shaped is quite a versatile 
material.

--- In  Randy Perretta <> 
wrote:
>
> I'd be real careful. Very few recorders go that low. Most bottom out at 20Hz. 
> They usually have DC blockingcaps on the inputs. Bass response is quite 
> commonly associated in quality with something that came from the wrong end of 
> the elephant. 
> 
> I just Googled for digital recorder frequency response. After a few pages, I 
> gave up. 20Hz is it. 
> 
> Maybe someone knows of something portable that goes to DC.  Personally, and 
> this is just me, Id be looking at scientific Or seismic gear (there's plenty 
> of infrasonic seismic gear out there suitable for field work) rather than 
> audio or contact the research staff at a place that does whale research and 
> see what they use.

PVDF Sensors or EMFIT Electret film coupled to a FET feeding one of the 
recorders from the wrong end of the elephant :) should suffice.

If the goal is to check the infra-sound, decimation & analysis in something 
like baudline  would also work. 

For scientific purposes a calibrated geophone or hydrophone with known 
sensitivity to a recorder that is a known quantity = used by other researchers 
providing you have the funds is the way to go.  No short cuts if you wish to 
compare data unless both systems are calibrated / measured & known.

BR
Mike.



> 
> Good luck,
> 
> Randy
> www.calmediaarts.com
>








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