# Question regarding beamforming on data acquired through sound card

Started by April 16, 2007
```I have taken data from single microphone in MATLAB work space through
MATLAB data acquisition tool box as left and right channels(inorder to
simulate the data from 2 microphones).Here is the code I have used for
sound data acquistion.

AI
duration = 2;
SampleRate = 44100;
set(AI,'SampleRate',SampleRate);
set(AI,'SamplesPerTrigger',duration*SampleRate);
set(AI,'TriggerType','Manual');
AI
start(AI);
AI
trigger(AI);
AI
X= getdata(AI);

To apply delay and sum beamforming,I should know the spacing between the
two microphones,the frequency of the source.How to know these
parameters.Also,can I take this problem as linear array problem.Here,I am
trying to align all sensor outputs by using the appropriate delays and
then summing all sensor outputs as Y. i apply code like this

Y=sum(abs(X*exp(-i*(2*pi*f/c)*d*m'*sin(Psi0))));

where X is the data we already obtained in MATLAB workspace.f is the
frequency of source,d is spacing between the microphone,m is [0
1]corresponding to linear array.Psi0 is the angle we will test for the
maximum power.

I would be thankful if I get some clear procedure about taking data from
microphone and how to use beamforming algorithm on this data(how to know
spacing between microphones and frequency of source if physically i have
only one microphone and i want to use data from left and right channels as
two microphones outputs).

Thanks for ur help
Sylvia

_____________________________________
Do you know a company who employs DSP engineers?
Is it already listed at http://dsprelated.com/employers.php ?
```
```Sylvia said the following on 16/04/2007 17:01:
> I have taken data from single microphone in MATLAB work space through
> MATLAB data acquisition tool box as left and right channels(inorder to
> simulate the data from 2 microphones).Here is the code I have used for
> sound data acquistion.
>
...
>
> I would be thankful if I get some clear procedure about taking data from
> microphone and how to use beamforming algorithm on this data(how to know
> spacing between microphones and frequency of source if physically i have
> only one microphone and i want to use data from left and right channels as
> two microphones outputs).

If you only have one microphone, you don't have a microphone array, so
you can't do beamforming!  If you attach the same microphone source to
both left and right channels, then clearly the data you receive will be
the same on each channel.

Technically, I suppose you could say that the separation distance is
therefore 0.  But this obviously won't be very useful.

--
Oli
```
```>Sylvia said the following on 16/04/2007 17:01:
>> I have taken data from single microphone in MATLAB work space through
>> MATLAB data acquisition tool box as left and right channels(inorder to
>> simulate the data from 2 microphones).Here is the code I have used for
>> sound data acquistion.
>>
>...
>>
>> I would be thankful if I get some clear procedure about taking data
from
>> microphone and how to use beamforming algorithm on this data(how to
know
>> spacing between microphones and frequency of source if physically i
have
>> only one microphone and i want to use data from left and right channels
as
>> two microphones outputs).
>
>If you only have one microphone, you don't have a microphone array, so
>you can't do beamforming!  If you attach the same microphone source to
>both left and right channels, then clearly the data you receive will be
>the same on each channel.
>
>Technically, I suppose you could say that the separation distance is
>therefore 0.  But this obviously won't be very useful.
>
>
>--
>Oli
>

I want to test the beamforming algorithms for uniform linear array.Now,I
need following questions to be answered.

1)If I have to use more than one microphone for applying beamforming
algorithms,what physical arrangement these microphones need to be(for
example,microphones need to be in line etc)

2)which sound card is better to get data from these multiple microphones

3)how do i get same sound data from multiple microphones into matlab
workspace using matlab sound acquisition tool box