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Re: Simultaneous recording with two digital recorders?

Subject: Re: Simultaneous recording with two digital recorders?
From: "soundings23" soundings23
Date: Sat Jun 9, 2012 1:50 am ((PDT))
Thanks Flawn ... and everyone ... fascinating responses as ever. I'm thinki=
ng this might actually work for one of the things I'm interersted in - reco=
rding quiet soundscapes. With the recorders are widely separated, the shari=
ng of detail will be minimised and audile drift not an issue.

Is the result of your project with multiple DATs available to listen to any=
where btw?



--- In  Flawn Williams <> wrote:
> David's notes are definitely germane for sound sources that are close to =
both mikes/recorders. It's not a good idea, for instance, to mike a piano w=
ith two separate recorders...the drift between the two clocks may be only s=
ay a quarter of a second across an hour, but the comb filter effect of the =
gradual shift will be audible.
> In a nature recording scenario, where the microphones/recorders may be se=
parated by many feet, the amount of audio that is common to both recordings=
 is tiny. If you already have many milliseconds of delay for sound arriving=
 at Recorder B from Point A and vice versa, the timing shifts due to clock =
errors are much less noticeable. I did a project for NPR/NGS a while back t=
hat involved five different portable DAT recorders capturing mikes that wer=
e as much as a hundred feet separate from one another. There was timing dri=
ft, but little audible effect.
> Timing drift has two components: steady drift (when two clocks are each v=
ery stable but slightly off one another) and variability (when a given cloc=
k has a range of frequencies that it drifts within). If steady drift is you=
r issue, then that can be corrected to minimize audibility using time compr=
ession or expansion in a computer DAW. If variability is the issue, it's mu=
ch harder to correct.
> If the recording is for scientific analysis, different standards of accep=
tability may apply than if the recordings are just for personal enjoyment o=
r for media release.
> --Flawn
> > 3n. Re: Simultaneous recording with two digital recorders?
> >    Posted by: "soundings23"  soundings23
> >    Date: Fri Jun 8, 2012 2:32 pm ((PDT))
> >
> > Thanks David, I may just try something without a common source as you s=
uggest. Following on from previous discussions, quiet soundscapes might wor=
k well. I'll just have a play and see what happens.
> >
> > --- In  "Avocet" <brini@> wrote:
> >>
> >> Tony,
> >>
> >> I've used two "toy" Tascams together with two pairs of stereo mics.
> >> Syncing the tracks is fiddly and needs more than a clap. With film
> >> recording a clapper board gives accuracy to the nearest frame, but if
> >> you want to match two sounds with a common source, you need better
> >> than millisecond accuracy. That's why I'm saving up for a 4-track.
> >>
> >> With timeode recorders, the timing accuracy is better than one frame
> >> per week or around one 10 parts per million. With two free-running
> >> affordable recorders you will get a drift which will produce flanging
> >> from a common sound source. If you don't have a common source, exact
> >> sync is not necessary anyway - just sync to a passing plane or
> >> whatever. :-)
> >>
> >> o.1 millisecond across a stereo image gives a noticeable shift in the
> >> image - that's 5 samples at 44.1 Ks/s. One part per million drift will
> >> produce that in around two minutes. Mixed, that produces a comb filter
> >> effect based on 1kHz.
> >>
> >> Point to ponder - how far away can a clapper board be before it is 1
> >> frame out of sync? That was one of my questions for trainees. :-)
> >>
> >> David
> >>
> >> David Brinicombe
> >> North Devon, UK
> >> Cogito cogito ergo cogito sum - Ambrose Bierce

"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.

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