At 3:30 PM -0700 5/7/07, Dan Dugan wrote:
>Rob Danielson, you wrote,
>
>>Please do point-out where the method method is lacking...
>>
>>The only ear evaluation _I_ do is match playback levels. I make the
>>high res files available so folks can tweak a test segment up or down
>>a dB or two to match to their tastes which is quite easy and quick to
>>do with QT Pro I might add.
>
>I think that's the weakest point--where a distinction in noise level
>of perhaps one or two dB is being made, trying to match clock ticks
>by ear is too chancy for me.
Dan & Raimund--
Sorry about the confusion around this. I don't use the clock ticks
for any sort of calibration or matching of playback levels. I use
the ticks and their variations to add some "life" to the
middle-ground which makes it easier for one to construct space out of
such minimal recordings (minimal because I must use multiple takes
with one pair of mics).
Consider comparing noise in a 744T pre with that of a HiMD's mic
pre--both at near full gain. So, what common reference sound should
the noise in both recordings be calibrated to?
When I use a 1K tone, 400 Hz tone or a pink noise tone centered at
200Hz, I'll get an obvious bump because of the difference in the
low-end response of the two preamps when the segments are butted
togethe (instead of being able to concentrate on the change in noise
at high frequencies). If I roll-off the bottom end under 250Hz, the
recording loses critical spatial cues and no longer sounds like a
recording of ambience. Although the Hi Hz noise can be accurately
referenced with a tone and rolling off all of the low end, the
resulting recordings are too ugly to listen to and evaluate.
Out of ideas, I tried matching the playback volume (by ear) of the
quietest moments of distant urban "rumble" from the 15 minute takes
made at ~2am and I found that I could usually get a fairly bump-free
bottom end. This meant, because of its poorer low-end response, the
recording from the Hi-MD recording, needed to be played about 1-2dB
louder to create the "match." When I thought about it, this didn't
bother me because the boost is consistent with the gain I would
employ were I to use the sound file as an ambient recording. (I
define the most distinct characteristics of ambience recording as a
sense of depth or distance stemming from differences in volumes and
cues from reflected sound waves. The first two octaves of sound
usually come from sources that are the farthest away, so using this
portion of the bandwidth is typically crucial for greatest depth.)
To check that my background levels are pretty well-matched in a test
I've asembled, I scramble copies of the regions on the timeline and
match them again from scratch until I get repeat settings.
Its not that I think that high Hz hiss is always the greatest concern
but rather I can't test for noise and other peculiarities under
1300Hz without an anechoic chamber or a studio in a remote area. I
hope to have the later some day because I want to understand lower
mid range performance much better. Rob D.
> I suggest a 1 KHz tone from a speaker between the clocks for level
>matching, calibrated by measuring voltage at the speaker terminals.
>You can leave it out of the
>published movie.
>
>-Dan Dugan
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
--
Rob Danielson
Peck School of the Arts
Department of Film
University of Wisconsin- Milwaukee
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