Combining Signals for Sound Card Line-In

Hey everybody,

I'm currently working on a sound-source localization project and was
hoping you could offer me some help.

First, I have two microphones which I am running to two amplifiers (one
for each signal). I want to read these signals with my PC sound card's
line-in and signal process using MATLAB. Can I simply connect a Y-cable
to combine the two amp outputs into a single, stereo input into my
line-in (and then use software to seperate it into right and left
channels for processing)?

Second, assuming I get the system set up and working statically, how
exactly does one go about running such a process
(record-->process-->repeat) in real-time? I'd really appreciate it if
anyone could give me a pretty basic overview of the vital concepts and
components of setting up said real-time system.

Thanks a lot for the help.

Polar wrote:
> Hey everybody,
> 
> I'm currently working on a sound-source localization project and was
> hoping you could offer me some help.
> 
> First, I have two microphones which I am running to two amplifiers (one
> for each signal). I want to read these signals with my PC sound card's
> line-in and signal process using MATLAB. Can I simply connect a Y-cable
> to combine the two amp outputs into a single, stereo input into my
> line-in (and then use software to seperate it into right and left
> channels for processing)?

A stereo signal is two channels of mono. What's to separate?

> Second, assuming I get the system set up and working statically, how
> exactly does one go about running such a process
> (record-->process-->repeat) in real-time? I'd really appreciate it if
> anyone could give me a pretty basic overview of the vital concepts and
> components of setting up said real-time system.

You write the program as a loop, and make it lean enough so  the loop 
can execute in the allotted time. A more detailed answer would require a 
more detailed question from you.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

"Jerry Avins" <jya@ieee.org> wrote in message 
news:BPCdnRSD15KxSvPeRVn-tA@rcn.net...
> Polar wrote:
>> Hey everybody,
>>
>> I'm currently working on a sound-source localization project and was
>> hoping you could offer me some help.
>>
>> First, I have two microphones which I am running to two amplifiers (one
>> for each signal). I want to read these signals with my PC sound card's
>> line-in and signal process using MATLAB. Can I simply connect a Y-cable
>> to combine the two amp outputs into a single, stereo input into my
>> line-in (and then use software to seperate it into right and left
>> channels for processing)?
>
> A stereo signal is two channels of mono. What's to separate?

The OP probably just means he would make the recording of both channels at once 
as a single stereo file and then separate it into two mono files with sound 
editor software.  If so, then yes, that should be no problem.  You just need to 
make sure you get the right Y-cable, i.e. one that combines 2 mono sources into 
stereo, rather than one that mixes 2 mono sources to mono.  I happen to have one 
sitting on my desk here that has 2 RCA jacks on one end and a stereo (aka 
tip-ring-sleave) 1/8" jack (i.e. like most headphones) on the other.  Something 
like that would be perfect.

>> Second, assuming I get the system set up and working statically, how
>> exactly does one go about running such a process
>> (record-->process-->repeat) in real-time? I'd really appreciate it if
>> anyone could give me a pretty basic overview of the vital concepts and
>> components of setting up said real-time system.
>
> You write the program as a loop, and make it lean enough so  the loop can 
> execute in the allotted time. A more detailed answer would require a more 
> detailed question from you.

You could try looking for some open-source recording software or libraries. 
Someone else may have a specific recommendation, but failing that, try 
http://www.google.com/search?hl=en&q=open+source+audio+record.