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Ng- Yes, I think the maximum cross-correlation value is what you want. That should get you delay between mics. You can also estimate relative amplitude to confirm which quadrant. -Jeff PS. Cool diagram. -------- Original Message -------- Subject: Re: Using PCM3003 to perform Sound localization Date: Thu, 13 May 2004 07:37:31 -0700 (PDT) From: ng enghsiung <> To: Jeff Brower <> Hi, Jeff Brower Thanks for answering so many question...for the cross correlation i have implemented but for detecting the delay....i got one question to ask...can?...the problem is--->i will show in the diagram.....the diagram was show in attachement thanks. From the diagram...the time delay for two sinewave is 0.305ms..this is observed from Matlab. If i implemented in C language...is't look at the peak point of the cross correlation? Is't Accurate? Because the number of point is presented as 1/fs..is't? Thanks Regards Eng Hsiung --- Jeff Brower <> wrote: > Ng- > > > Thanks for you reply, do you know how to measure > the wavefront > > (source to mics) or what is estimation > measurement? Because i got one > > problem in measuring the angle at the different > distance (source to > > mics) and the resulting of the angle are always > different at the > > different distance. It is have any algorithm can > solve the problem? > > > > Is't when frequency changing the resulting angle > with be change at > > the same position? > > > > How to estimation error bounds in real time > system? > > Not sure... you are asking algorithm / > application-specific questions rather than DSP > questions. But I might suggest you use a sweep > rather than constant sine function. > for a constant wave it will be hard to get delay > accurately. Have the source sweep > from dc to half your PCM3003 capability (approx 20 > kHz), then perform a > cross-correlation function between the mic inputs > and you should be able to obtain a > reasonable estimate of delay. > > -Jeff > > > --- In , Jeff Brower > <jbrower@s...> wrote: > > > Ng- > > > > > > > Thanks for your reply. > > > > > I'm curious -- how is it going with this? > Once you > > > > > have PCM3003 daughtercard > > > > > correctly configured (for 48 kHz Fs, I > assume) and > > > > > algorithm is correct, are you able > > > > > to get past 45 deg with real signals? > > > > > > > > Ya i got the sampling approximately 48kHz and > the > > > > simulation given angle is around 45 to -45 > degree. > > > > what that simulation is only work for this > range? is't > > > > because of the "sin" function? how to solve > that > > > > problem so that i can get the angle or > direction from > > > > 180 to -180 degree. > > > > > > I think you mean 90 to -90 -- with only 2 mics > you cannot resolve > > between front and > > > rear. > > > > > > > > How far apart are your microphones? > Depending on > > > > > the sampling rate, you will need > > > > > some minimum separation to obtain correct > results... > > > > > > > > i'm just use the microphone from the PCM 3003, > it will > > > > cause the problem or not? Because i still can > not get > > > > the right angle in real time system. Actually > i have > > > > try using external pre-amp (two microphone > also) to > > > > test that simulation but still give me the > problem. > > > > Is't the distance between the microphone will > cause > > > > the problem to getting the angle or direction? > > > > > > > > Experiment set-up > > > > The distance between source and microphone > > > > approximately 60cm (more that one wavelength). > and > > > > distance between micphone approximately 6cm. > > > > > > > > > Also, are you connecting mics directly to > PCM3003? > > > > > Will that work, or does it > > > > > require line-level input? > > > > > > > > Ya it was. but only work for 45 to -45 degree. > > > > > > I would record stereo signal at 90 deg and look > at it with software > > to verify about 9 > > > sample delay between L and R channels (for mic 6 > cm apart). That > > will check your > > > sampling rate and other assumptions. > > > > > > -Jeff > > > > > > > > -Jeff > > > > --- Jeff Brower <jbrower@s...> wrote: > > > > > Ehng3 > > > > > > > > > > > I am currently do some testing in sound > > > > > localization, but now i got > > > > > > one problem.........still can not be > solve......:( > > > > > > > > > > > > The ALgorithm located on his book "DSP > > > > > Applications using C and the > > > > > > TMS3206x DSK" "Page 268 Acoustic Direction > > > > > Tracker". There are no > > > > > > problem for the simulation, when the input > signal > > > > > injected by > > > > > > function generators directly, but when the > input > > > > > signals coming from > > > > > > real world (microphones buit-in > PCM3003)then the > > > > > simulation is only > > > > > > can allocate/detect the angle from > approximatly 45 > > > > > degree to -45 > > > > > > degree...why? > > > > > > > > > > > > First i guess the problem may come from > echo and > > > > > noise....but the > > > > > > simulation can work in function generators > > > > > signal.... why it can not > > > > > > work in real world signal?? Any idea??? > Please... > > > > > > > > > > > > Same Algorithm, the equation given from > the > > > > > book....c=arcsin > > > > > > (a/b),......the time delay > (phase/frequency)....is > > > > > the frequency as > > > > > > input frequency and the phase is > difference phase > > > > > from FFT? > > > > > > > > > > > > Is't the setting jumper for PCM 3003 from > the book > > > > > has a mistake? > > > > > > So, what is the actuall setting and > maximum > > > > > sampling frequency for > > > > > > PCM3003? Do you have latest setting > manual? > > > > > Please... > > > > > > > > > > I'm curious -- how is it going with this? > Once you > > > > > have PCM3003 daughtercard > > > > > correctly configured (for 48 kHz Fs, I > assume) and > > > > > algorithm is correct, are you able > > > > > to get past 45 deg with real signals? > > > > > > > > > > How far apart are your microphones? > Depending on > > > > > the sampling rate, you will need > > > > > some minimum separation to obtain correct > results... > > > > > > > > > > Also, are you connecting mics directly to > PCM3003? > > > > > Will that work, or does it > > > > > require line-level input? > > > > > > > > > > -Jeff | |||
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