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Date: Tue Jul 27, 2010 6:12 pm ((PDT))
Hi Dan,
I'm leaving Bloomington on Saturday and only will be in the country until t=
he 9th August, so I figured I should touch base about where the Uher and Na=
gra stand. I recall you writing that the Nagra was done, and that you had a=
lready done 1 hr on the Uher. I don't know if you've proceeded with more wo=
rk or not, but I wanted to make sure there was enough lead time for me to r=
eceive the machines from you.
Also, I can pay this first invoice you've sent now, or would you prefer I p=
ay both the Nagra and Uher service together? And, would you like me to pay =
by check, paypal, or CC? I can call it in tomorrow if that is your preferen=
ce.
Thanks so much,
Vlad
Wolodymyr Smishkewych
wolodymyrsmishkewych.com
On 27 Jul 2010, at 18:43, Dan Dugan wrote:
> >>> Here's a blind comparison movie created from the results of a moving
> >>> pink noise test that is hopefully very similar to what Dan suggested.
> >>> The (3mb .zip) download link is at the bottom of the blog post here:
> >>> <http://tinyurl.com/2egg33s>http://tinyurl.com/2egg33s Play it
> >> with QuickTime or a
> >>> QuickTime-compatible player on your computer.
> >>
> >> Very nice, thank you, Rob.
> >>
> >> I've posted a Spectrafoo sonogram of the MP3 at:
> >>
> >> <http://www.dandugan.com/downloads/Miscellany/20100726_BoundaryCombFil=
tering.png>http://www.dandugan.com/downloads/Miscellany/20100726_BoundaryCo=
mbFiltering.png
> >>
> >> and another with higher gain trying to show the highest frequencies be=
tter
> >>
> >> <http://www.dandugan.com/downloads/Miscellany/20100726_BoundaryCombFil=
tering_2.png>http://www.dandugan.com/downloads/Miscellany/20100726_Boundary=
CombFiltering_2.png
> >>
> >> The most audible effects I hear are a descending tonal effect in the
> >> mid-range and the directivity of the mics at high frequencies (HF
> >> comes up as pan comes on axis). Both happen on all three mountings.
> >> I don't understand the source of the mid-range effect.
> >>
> >> Comb filtering effects at the top end that were my concern when I
> >> proposed the test are more subtle than I expected. I found it useful
> >> to high-pass the playback way up like 5k-8K to eliminate the
> >> distractions of the lower effects.
> >>
> >> -Dan
> >>
> >
> > Hi Dan--
> >
> > Both files I posted are full res (movie's soundtrack 16/48K and .wav
> > 24/48K). So no mp3 artifacts should be involved.'
>
> I was mistaken in saying MP3.
>
> > I'm noticing a dropping chord with a fundamental around 407 Hz that
> > changes to about 347 Hz in all samples.
>
> Exactly.
>
> > It sounds a bit like a
> > Doppler effect but that doesn't seem possible as the speaker isn't
> > getting closer and the velocities are so low. Could it be something
> > like a difference tone created by sliding pitch changes high in the
> > spectrum? Yet, that would be psychoacoustic and there may be a faint
> > trace of the 407- 347 Hz drop in the sonograms.
>
> I don't think so. Any reflective surface other than the ground nearby? Ef=
fect of the ground should be constant unless you actually changed elevation=
as you moved...comb filter effects are very sensitive to small differences=
.
>
> > Can one tell if the steep, downward sloped bands in the last 2/3rds
> > of the A samples and the less steep upwards sloped bands in the last
> > half of C samples is comb filtering?
>
> That's how I interpret them.
>
> > My older ears are pressed to
> > detect this HF content . Rob D.
>
> Me, too, after high-passing 12dB/oct at 8K I hear a little something just=
at the end of #1, and swishing in no. 3.
>
> -Dan
>
>
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