Curt Olson, you wrote,
>I stepped up your audio clips and imported them to
>ProTools for a quick mono-compatibility check. The hat-mounted 3032s
>seemed very good, and much better than the vest-mounted 183 pair.
I've just checked them in mono, too. I can think of two problems that
a mono sum can have: 1) loss of sounds that are primarily out of
phase, and 2) colorations or frequency-area cancelations due to
summing mics at different distances from a source.
I'm embarrassed to admit that I've never mono-checked the
spaced-omnis-with-barrier recordings that I've been making for
several years! I checked the Muir Woods samples in mono today. I was
pleasantly surprised that neither of the problems above seemed
evident to me. I think either all the sound elements in the scene
were so diffuse that summing didn't affect tonality, or the the
barrier technique was effective in preventing interference in the
frequency range where it's audible.
Of course the lower noise of the 3032s made their mono sum clearer,
and the summing increased the veiling of the soundscape with the
noisier mics. But I view this as more an amplification of the
differences that were apparent in stereo rather than a particular
summing effect. After all, both pairs were similarly spaced with
similar barriers.
With more listening I have to say that it wasn't an entirely fair
comparison, because the two arrays weren't in the same place. I
suspect that the revelation of the water sounds in the 3032 segments
was due as much to position as it was to noise veiling. The log where
I was sitting was on a slight shoulder of the trail, and I think I
had a direct view of a small tributary stream a couple of hundred
feet down the slope, but Sharon, twenty feet farther up the trail,
may have been "over the hill" from that sound. It could also be an
effect of cheap vs. state-of-the-art A/D converters, but I doubt
that. If the converters in the Sharp MD were reducing low-level
sounds, they would have reduced the mic hiss, too. Next time we're
out I'll try to do some side-by-side comparisons.
When I turned it way up I noticed that I can hear Sharon's breathing
in my recording, too. I also noticed that there's a rumble at the
bottom end of the 3032/722 recording that the 183/MD combo didn't
pick up. On a Spectrafoo analyzer the ambience starts rising below
100 Hz and keeps on rising all the way down to 6 Hz. I suspect this
was the ocean, but it could be self-noise of the mics. I don't know
any place quiet enough to resolve that; as Rob Danielson said the
other day, low frequencies travel great distances.
-Dan Dugan
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