Which micros should I buy?

Hi,
I need some help to decide which type of microphone would be best
suitable for a 1D linear audio array for sound source localisation and
beamforming. In the moment I have pretty cheap omnidirectional electret
condenser microphones. But the problem is that the computet AOA is only
quite accurate really close ( <=1m ) to the array which is a result of
I think the low SNR of the signals. Unfortunately I would like to use
it in an area up to 4 or 5 meters and do then beamforming in this area
as well.

Therefore I would like to buy some better microphones, but I don't know
really which ones are good for this task and if an omnidirectional or a
cardioid would be better? Sure my array design will matter. Currently
my micros are position horizontally at a wall, so that the micros point
to the opposite wall of the room. Therefore I think a micro with a
cardioid polar pattern would make sense. Is it right, that for a micro
with a cardioid pattern I would have to turn the micros by 90 degree so
that they the point towards the ceiling?

In the moment I'm thinking of buying this: (Which is also roughly the
most I
can spent on one micro)

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

Thanks for any suggestion!!!!

Cheers

Thorsten

Thorsten wrote:
> Hi,
> I need some help to decide which type of microphone would be best
> suitable for a 1D linear audio array for sound source localisation and
> beamforming. In the moment I have pretty cheap omnidirectional electret
> condenser microphones. But the problem is that the computet AOA is only
> quite accurate really close ( <=1m ) to the array which is a result of
> I think the low SNR of the signals. Unfortunately I would like to use
> it in an area up to 4 or 5 meters and do then beamforming in this area
> as well.
> 
> Therefore I would like to buy some better microphones, but I don't know
> really which ones are good for this task and if an omnidirectional or a
> cardioid would be better? Sure my array design will matter. Currently
> my micros are position horizontally at a wall, so that the micros point
> to the opposite wall of the room. Therefore I think a micro with a
> cardioid polar pattern would make sense. Is it right, that for a micro
> with a cardioid pattern I would have to turn the micros by 90 degree so
> that they the point towards the ceiling?
> 
> In the moment I'm thinking of buying this: (Which is also roughly the
> most I
> can spent on one micro)
> 
> http://www.behringer.com/ECM8000/index.cfm?lang=ENG

It seems to me that unless you are prepared to account for and exploit 
in software whatever directionality the microphones may have, the closer 
to omnidirectional they are, the better. That usually means small, and 
that in turn implies relatively inexpensive.

Microphones differ in sensitivity, but the SNR you get is probably 
determined more by the room than by the microphone. At close range, 
reflection matters less and distant noise sources are better masked. 
Reflections can be handled by better room modeling, but noise -- the air 
conditioner in the next room, for example -- are best dealt with at the 
source.

Another improvement that close proximity provides is greater angular and 
path-length difference from the source to individual microphones. I 
would consider all these variables carefully before spending money on 
new microphones.

Jerry

P.S. In this business, "micro" usually means microprocessor.
-- 
Engineering is the art of making what you want from things you can get.
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