Integrate PDM to PCM?

On Saturday, October 22, 2016 at 6:27:14 PM UTC-4, Tom Becker wrote:
> > Have you tried making your own elements?
> 
> No, but maybe someday I'll tinker with a 30mm Polaroid 200V electrostatic but I am, for now, put off by the patterns that large-diaphragm sensors exhibit.  High voltage is surely also more problematic.
> 
> I don't want narrow lobes.  I enjoy recording in stereo to hear the bat flight dynamics; omnidirectional, figure-eight and cardioid patterns, sometimes recorded in Mid-Side which allows manipulating the pattern later, suit that well.
> 
> Most government, commercial and academic bat freaks are seeking species identification and population counts best achieved with more directional mics (for which more than one company gets $1200 each: http://www.ultrasoundgate.com, for example).
> 
> The equipment is often exposed to dew that requires conformal coating and heaters to combat.  My mics have eight resistors that warm the assembly to prevent condensation and consequential corrosion - an instant serious noise generator - and that's at 12-48V.  I expect 200V must be a PITA.
> 
> 
> Tom

"Most government, commercial and academic bat freaks are seeking species identification and population counts best achieved with more directional mics (for which more than one company gets $1200 each: http://www.ultrasoundgate.com, for example). "

Wow !

Those "bat freaks" certainly have some bucks to spare cause this route is more expensive than the one I suggested (e.g. National Instruments DAQ hardware)

I also would say that (sufficiently large) array of omni-directional microphones is much better than few directional mics - you can point it in any direction at any point in time, e.g. after recording is done  

angrydude  <simfidude@gmail.com> wrote:

>I also would say that (sufficiently large) array of omni-directional
>microphones is much better than few directional mics - you can point it
>in any direction at any point in time, e.g. after recording is done  

Excellent idea. 

I know form folks in the National Park Service that they deploy
many many audio sensors for wildlife detection.  If they are not
using the above beamforming approach presently, they certainly should be.

Such a technique might also make it possible to detect bat sounds and 
other animal sounds with an overhead system, such as a blimp.  

Steve

> ... beamforming...

One very intriguing feature of InvenSense's TDM mics is that currently up to 16 elements can be daisy-chained in an array and sampled simultaneously at 48kHz.  Data is then clocked out at ~3MHz on a single data line, 24 two's complement bits per element.  Not good for ultrasonics, but for an audible-audio steered beam it'd be great.  I suspect it would take a lot of array processing power.

See pg 12: https://www.invensense.com/wp-content/uploads/2016/10/DS-000121-ICS-52000-data-sheet-v1.1.pdf

Tom