Posted by Jan Panteltje on 07/21/07 14:44

On a sunny day (Wed, 18 Jul 2007 04:54:53 GMT) it happened "Mark & Mary Ann
Weiss" <mweissX294@earthlink.net> wrote in
<x2hni.91717$oA4.68481@fe04.news.easynews.com>:

>>The V1U had an external condenser mic on the same stand as those feeding the
>>HV20.
>>Finally, the Zoom H4, with external condenser mics made the third recording.
>>
>>Sony doesn't look very good in this TYPICAL scenario which wedding
>>videographers will encounter frequently.
>>
>>
>>
>>Best Regards,
>>
>>Mark A. Weiss, P.E.
>>www.mwcomms.com

I wrote:
>The Zoom H4 is really amazing is not it?
>It sure gets the most natural sound in my view.


I want to add something to my remark.
The reason why I prefer the Zoom H4 sound.
I listened to the 3 mp3 examples with Senheiser headphones (the closed type), and
in the mike setup for both the Canon and Sony (so nothing to do with the cameras),
the voices reach the ear so far apart in time that you perceive these as 2 different sounds.
Not echo, but the one ear earlier then the other.
This breaks the stereo phase, although it gives an interesting spatial picture.
However if displayed on say a wide screen you will not be able to locate the position,
of for example the kid walking about, from the sound.
The Zoom H4 seems to have the mikes very close, on a natural distance (like our ears)
from each other, and you can hear the kid walking around, and where he is.

If we look at theory (I wrote some small utilities just for this some time ago),
this makes sense.
I found 'stereo' breaks if the delay between channels is more then a few milli seconds.
It then falls apart as 2 different signals.
Unlike amplitude changes only, (like in a stereo pan on an amplifier by changing left
right volume), you also have stereo perception (and much more actually) because of phase.
To make it simple: If the maximum of say a 1 kHz tone reaches the left ear earlier
then the right ear, the brain interprets that as the source is on the left!
The math:
Say if your ears are 20 cm apart, then the sound that travels 330 m/s, so 33 cm/ms,
takes about .6 mS to go from left ear to right ear.
If the frequency is 1 kHz, so 1 mS period time, that is large part of the period
of the wave!
So for a correct stereo pattern the phase relationship difference between left and right COUNTS!
Unlike those that claim phase is ignored in the ear ..... it is an important factor
we use it to locate sound sources.
Thank you for your attention.
*This* is what makes the Zoom H4 stereo pattern so good, the mike positions.

I found this out when I wrote some utilities to get rid of the main language in a
translation channel, subtracted the main language from the translation channel that
also had the main language in it, to wind up with only the translation.
The signals were slightly delayed (went trough a different signal chain) so I added
a variable delay (by simply shifting samples in the wave files).
There is a point where the position info the brain perceives, 'breaks', and no longer
any location can be pointed out for the sound source, and before that point
shifting (delaying) a few samples moves the sound source from extreme left to extreme right!
(for a mono sound source).
I used the effect to get dead centre, dead centre was the right phase to subtract the
unwanted signal.

Now I am not saying 'always put the mikes like the Zoom H4 has these (and at that distance)',
but I *am* saying 'if you really want true stereo, where left in picture sounds left, you will
likely have to do that :-)'

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