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Sound Localization

Started by Karthik Ravikanti March 1, 2005
Hi,
I'm Back again.
This time I have a different problem....


I tried to record a sinusoidal tone using a pair of microphones by
plugging the microphones into the line-in port of my sound card. I used
Sony Sound Forge to record the signal.But what i saw was that both the
channels were identical.It seemed like the recorded file was a sum of
the individual mic ouputs. I connected the mics to the line in using a
Dual Mono female to Stereo Male Jack.
Is there anyway I can actually record the channels separately, i mean
the left mic's output should come in the left channel and right mic in
the right channel.

Thanx in advance,

Karthik Ravikanti

http://students.iiit.net/~karthik_ravikanti

Let there be Sound!!!

Karthik Ravikanti wrote:
> Hi, > I'm Back again. > This time I have a different problem.... > > > I tried to record a sinusoidal tone using a pair of microphones by > plugging the microphones into the line-in port of my sound card. I used > Sony Sound Forge to record the signal.But what i saw was that both the > channels were identical.It seemed like the recorded file was a sum of > the individual mic ouputs. I connected the mics to the line in using a > Dual Mono female to Stereo Male Jack. > Is there anyway I can actually record the channels separately, i mean > the left mic's output should come in the left channel and right mic in > the right channel. > > Thanx in advance, > > Karthik Ravikanti > > http://students.iiit.net/~karthik_ravikanti > > Let there be Sound!!!
Is your line-in jack stereo? (I think your adapter was a dual mono jack to stereo plug.) Using a stereo plug in a mono jack connects only the tip, not the ring. Are the two channels numerically the same, or only their waveforms? The same waveform is to be expected when two microphones record the same sound. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
"Jerry Avins" <jya@ieee.org> wrote in message
news:D9udndjZVZNfPLnfRVn-tg@rcn.net...
> Karthik Ravikanti wrote: > > Hi, > > I'm Back again. > > This time I have a different problem.... > > > > > > I tried to record a sinusoidal tone using a pair of microphones by > > plugging the microphones into the line-in port of my sound card. I used > > Sony Sound Forge to record the signal.But what i saw was that both the > > channels were identical.It seemed like the recorded file was a sum of > > the individual mic ouputs. I connected the mics to the line in using a > > Dual Mono female to Stereo Male Jack. > > Is there anyway I can actually record the channels separately, i mean > > the left mic's output should come in the left channel and right mic in > > the right channel. > > > > Thanx in advance, > > > > Karthik Ravikanti > > > > http://students.iiit.net/~karthik_ravikanti > > > > Let there be Sound!!! > > Is your line-in jack stereo? (I think your adapter was a dual mono jack > to stereo plug.) Using a stereo plug in a mono jack connects only the > tip, not the ring. > > Are the two channels numerically the same, or only their waveforms? The > same waveform is to be expected when two microphones record the same sound.
Line in jacks are almost always stereo on modern PCs. A quick test would be to unplug one of the microphones, re-record, and make sure one the channels go away. If not, you have a problem somewhere with your adapters, sound hardware, or software settings. I'm guessing that you actually plugged the microphones into the microphone input rather than the line input. I say this because normally a microphone plugged into a line input would normally give an extremely low level signal or nothing at all (if the microphone requires power). But that's just a guess.
Jerry Avins wrote:

> Karthik Ravikanti wrote: > >> Hi, >> I'm Back again. >> This time I have a different problem.... >> >> >> I tried to record a sinusoidal tone using a pair of microphones by >> plugging the microphones into the line-in port of my sound card. I used >> Sony Sound Forge to record the signal.But what i saw was that both the >> channels were identical.It seemed like the recorded file was a sum of >> the individual mic ouputs. I connected the mics to the line in using a >> Dual Mono female to Stereo Male Jack. >> Is there anyway I can actually record the channels separately, i mean >> the left mic's output should come in the left channel and right mic in >> the right channel. >> >> Thanx in advance, >> >> Karthik Ravikanti >> >> http://students.iiit.net/~karthik_ravikanti >> >> Let there be Sound!!! > > > Is your line-in jack stereo? (I think your adapter was a dual mono jack > to stereo plug.) Using a stereo plug in a mono jack connects only the > tip, not the ring. > > Are the two channels numerically the same, or only their waveforms? The > same waveform is to be expected when two microphones record the same sound. > > Jerry
He may have done everything and got *EXACTLY* the correct answer. Assume two identical mikes ( Same make and model may be sufficient. Same production run might be even more favorable. ) Place mikes at points "A" and "B". Place sound source *ANYWHERE* on perpendicular bisector of line AB. Would not signals have *IDENTICAL* amplitude and phase ;} I would suggest placing mike at point "M" such that: 1. MAG(MA) > MAG(MB) 2. MAG(MA) >> MAG(AB) 3. wavelength of tone <> rational multiple of any of distances involved ( <> integer multiple *might* be sufficient )
Richard Owlett wrote:

   ...

> He may have done everything and got *EXACTLY* the correct answer. > > Assume two identical mikes ( Same make and model may be sufficient. Same > production run might be even more favorable. ) > > Place mikes at points "A" and "B". > Place sound source *ANYWHERE* on perpendicular bisector of line AB. > > Would not signals have *IDENTICAL* amplitude and phase ;} > > I would suggest placing mike at point "M" such that: > 1. MAG(MA) > MAG(MB) > 2. MAG(MA) >> MAG(AB) > 3. wavelength of tone <> rational multiple of any of distances involved > ( <> integer multiple *might* be sufficient )
A challenge to you: Use two mikes, as identical as you can get. Place them wherever you like, accounting for reflections from the surroundings. Place a sound source as best you can measure in their perpendicular bisecting plane. Record the source in such a way as to make the numbers in the two recorded channels identical, as it one had been copied from the other. Do you think you can do it? I don't. I think the channels will generate nearly identical waveforms on playback, but I'm sure the actual numbers will differ. Doesn't that conform to what I wrote? Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Jerry Avins wrote:

> Richard Owlett wrote: > > ... > >> He may have done everything and got *EXACTLY* the correct answer. >> >> Assume two identical mikes ( Same make and model may be sufficient. >> Same production run might be even more favorable. ) >> >> Place mikes at points "A" and "B". >> Place sound source *ANYWHERE* on perpendicular bisector of line AB. >> >> Would not signals have *IDENTICAL* amplitude and phase ;} >> >> I would suggest placing mike at point "M" such that: >> 1. MAG(MA) > MAG(MB) >> 2. MAG(MA) >> MAG(AB) >> 3. wavelength of tone <> rational multiple of any of distances involved >> ( <> integer multiple *might* be sufficient ) > > > A challenge to you: > > Use two mikes, as identical as you can get. Place them wherever you > like, accounting for reflections from the surroundings. Place a sound > source as best you can measure in their perpendicular bisecting plane. > Record the source in such a way as to make the numbers in the two > recorded channels identical, as it one had been copied from the other. > > Do you think you can do it? I don't. I think the channels will generate > nearly identical waveforms on playback, but I'm sure the actual numbers > will differ. Doesn't that conform to what I wrote? > > Jerry
Ahh, but what is discernible difference. Then again how about "free field" &/or "anechoic chamber"? OP did not specify how signals were compared. ;}
"Richard Owlett" <rowlett@atlascomm.net> wrote in message
news:1129pnfqcbebp84@corp.supernews.com...
> Jerry Avins wrote: > > > Richard Owlett wrote: > > > > ... > > > >> He may have done everything and got *EXACTLY* the correct answer. > >> > >> Assume two identical mikes ( Same make and model may be sufficient. > >> Same production run might be even more favorable. ) > >> > >> Place mikes at points "A" and "B". > >> Place sound source *ANYWHERE* on perpendicular bisector of line AB. > >> > >> Would not signals have *IDENTICAL* amplitude and phase ;} > >> > >> I would suggest placing mike at point "M" such that: > >> 1. MAG(MA) > MAG(MB) > >> 2. MAG(MA) >> MAG(AB) > >> 3. wavelength of tone <> rational multiple of any of distances involved > >> ( <> integer multiple *might* be sufficient ) > > > > > > A challenge to you: > > > > Use two mikes, as identical as you can get. Place them wherever you > > like, accounting for reflections from the surroundings. Place a sound > > source as best you can measure in their perpendicular bisecting plane. > > Record the source in such a way as to make the numbers in the two > > recorded channels identical, as it one had been copied from the other. > > > > Do you think you can do it? I don't. I think the channels will generate > > nearly identical waveforms on playback, but I'm sure the actual numbers > > will differ. Doesn't that conform to what I wrote? > > > > Jerry > > > Ahh, but what is discernible difference. > > Then again how about "free field" &/or "anechoic chamber"? > > OP did not specify how signals were compared. ;}
In the real-world, the left and right channels of a stereo input are going to be numerically different, even if the exact same signal is fed to both. Such is the effect of noise (not to mention slight gain mis-matches, etc.). But Richard is correct that the OP didn't specify if the 2 channels sounded the same, the waveforms looked the same, or the numbers were exactly the same. That would be helpful information to have.
Richard Owlett wrote:

   ...

> OP did not specify how signals were compared. ;}
You specified that: "*EXACTLY*". I asked him. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Jerry Avins wrote:
> Karthik Ravikanti wrote: > > Hi, > > I'm Back again. > > This time I have a different problem.... > > > > > > I tried to record a sinusoidal tone using a pair of microphones by > > plugging the microphones into the line-in port of my sound card. I
used
> > Sony Sound Forge to record the signal.But what i saw was that both
the
> > channels were identical.It seemed like the recorded file was a sum
of
> > the individual mic ouputs. I connected the mics to the line in
using a
> > Dual Mono female to Stereo Male Jack. > > Is there anyway I can actually record the channels separately, i
mean
> > the left mic's output should come in the left channel and right mic
in
> > the right channel. > > > > Thanx in advance, > > > > Karthik Ravikanti > > > > http://students.iiit.net/~karthik_ravikanti > > > > Let there be Sound!!! > > Is your line-in jack stereo? (I think your adapter was a dual mono
jack
> to stereo plug.) Using a stereo plug in a mono jack connects only the
> tip, not the ring. > > Are the two channels numerically the same, or only their waveforms?
The
> same waveform is to be expected when two microphones record the same
sound. I don't know this particular software, nor do I know how you compared the two sounds. You should be aware, though, that visualization and plotting routines generally don't have the same resolution as the numbers in your sound file. So if you have little time delay between channels and and "almost equal" data, they might well look equal when plotted on screen. I would suggest you try to plot the arithmetic difference between the two channels, i.e. channel(A) - channel(B). If this difference is exactly 0, then I'd get a bit worried. Rune
Hi,

I did try plugging out one of the microphone, and still the other
channel does not go out.

I also know that both the channels are identical because i calculated
the time delay by cross-correlating them in Matlab, and the delay came
out to be zero.

I did not connect them into mic in,coz i know  line-in is blue. The
signal was not extremely low because i amplified it before sending it
in.

My sound source was not on the perpendicular bisector either, it was at
50 degrees to the bisector.
Once, I connected both the microphones and put them far away(there was
a wall between them too), and asked a friend to speak into one while I
did into another. Guess what? Both of our voices were heard in both the
channels!

Is it the line-in jack,or the sound card, or my Dual-mono to stereo
jack. Whose the culprit???

Any guesses?

And can anyone confirm the fact that a Blue Jack is always a stereo
jack?(coz thats what i heard).

Do I have to use a dual line-in sound card???