Some question regarding the use of array of microphones.

[Gaurang]

Hi,
I am doing a project on audio source localization using 4 microphones (not something new) using TI DSP. I do not have an audio background, hence the silly questions. Please assume that the possible combination of line inputs and mic inputs are available. I would really appreciate if you could give me some options, suggestions or hacks.

1. Can I combine and later on split audio from 2 Electret microphones (after the required pre-amplification) using a stereo line input. And hence I could use 2 stereo line inputs for the 4 microphones.
2. Or do I need 4 different line inputs for 4 pre-amplified Eectret(Ec) microphones.
3. Or can I just use 4 mic inputs for the 4 Ec micrphones.
4. Is the line input (default that comes with commonly available soundcards) a stereo line input or a mono line input.

That's all for now.
Thanks in advance. I appreciate any help.

[sabianq]

HI
you are on the right track,
here is something about pro audio.

it can be argued that there is really no such thing as "stereo" in the pro audio world.
we have input channels and output mixes
Stereo is actually two (2) channels with each panned to the right and left main output of the mixer.

a mixer takes multiple channels and "mixes" then down to be routed to different outputs like an AUX, Bus or Main Mix.

so to answer your question/s

1. Can I combine and later on split audio from 2 Electret microphones (after the required pre-amplification) using a stereo line input. And hence I could use 2 stereo line inputs for the 4 microphones.

Yes, assuming you have the equipment that will allow you to "record" up to 4 channels.
in order to "split" a "stereo" mix, all you have to do is record 2 different microphone inputs into a "stereo" recording, they need to be hard panned (meaning you need to pan each microphone all the way to the right and left independently to minimize cross talk between the channels)
on play back you will have two channels with the "right channel" as one microphone and the left channel as the other microphone.

if you record 4 channels and want to later split the microphones into individual microphones (called tracks, ) (your interface needs to be able to accept 4 independent channels and you need software that will allow you record multiple tracks).

2. Or do I need 4 different line inputs for 4 pre-amplified Eectret(Ec) microphones.

now you can record two seperate stereo channels (4 channels) but if you bounce down or mix down the tracks to a 2 channels stereo track, the information will be lost and you cannot seperate the 4 microphones in the future.
so if you keep a 4 track mix of the microphones on your DAW (digital audio workstation) software, then you can isolate the independent microphones later.

3. Or can I just use 4 mic inputs for the 4 Ec micrphones.

yes 4 microphone inputs will also work assuming your AD/DA (analogue to digital interface) can accept 4 channels in.

4. Is the line input (default that comes with commonly available soundcards) a stereo line input or a mono line input.

yes, the Line in should be 2 channels or a stereo input,
however if you want to record 4 channels using a single stereo input, you need to make 2 seperate recordings onto 2 stereo tracks giving you 4 channels.

you cannot make a simultaneous 4 track recording using a sound card with only 2 channels in, you would need to record your sample using a stereo pair of microphones into a stereo track or two mono tracks then go back and record your sample again onto another stereo or two mono tracks giving you a total of 4 tracks.

i hope this helps
cheers!

[130dB]

As a supliment to what sabianq said, most recording software will see a "stereo" input as two inputs that can either be recorded to a single two channel "stereo" track, or to two separate mono tracks.

[Gaurang]

Thank you guys, It surely helps a lot to clear these things from the experts.
Thanks again.
I will ask more questions as I progress through the project or I do not understand anything.
I appreciate it.-