Sound Localization using Sound Amplitude

"Eric Jacobsen"  wrote in message 
news:4e1b9db6.38140731@www.eternal-september.org...

On Mon, 11 Jul 2011 20:34:11 -0400, "Phil Martel"
<pomartel@comcast.net> wrote:

>
>
>"Fred Marshall"  wrote in message
>news:50ISp.87892$fD6.45795@en-nntp-02.dc1.easynews.com...
>
>On 7/11/2011 7:15 AM, Clay wrote:
>
>>
>>
>> Hello Fred,
>>
>>
>> You can take 2 different sets of data for the same signal where the
>> only essential difference is the time delay and frequency offset and
>> then do a frequency domain approach to the TDOA. For example find the
>> DFT of each signal. Then conjugate one of the signals and then form a
>> sample by sample inner product between the two. The find the argument
>> of each resulting sample. When plotted (argument vs sample(frequency
>> bin) you will get a straight line whose slope is the time offset and
>> intercept is the frequency offset. Notice how the TDOA and the
>> frequency offset get separated out in the analysis - I found this
>> quite useful in RF applications when I didn't have to worry about
>> carrier and doppler frequency offsets.  You can even weight the
>> samples by their spectral power before doing the regression fit.
>>
>> This is basically doing TDOA autocorrelation via FFT except for the
>> converting back to the time domain and peak search.
>>
>>
>> Clay
>>
>>
>>
>
>Ah!  OK.  Thanks Clay.
>
>Fred
>
>Hi,
>
>The approach we used was somewhat different, but probably isomorphic.
>We FFTed each channel, summed the magnitude squared then selected peak
>frequencies,
>then took the phase difference at a given peak between one channel and each
>of the others.
>From that information and the geometry of the array, we were able to
>determine the DOA of the signal at that frequency.
>
>   Best wishes,
>   --Phil
>

How well did that work?   I've been thinking of using a very similar
technique for a slightly different application.


Eric Jacobsen
http://www.ericjacobsen.org
http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php

Reasonably well.  We were getting about 3 degrees RMS error with good S/N, 
in-an-open-field sorts of situations.