Anders, what exactly does "trim the view of noisefloor" do? Does it actuall=
y remove noise before calculating the spectrogram, or does it just use tric=
ks like adjusting image brightness and contrast or despeckling?
I use the spectrogram in Audacity to scan through my recordings, although t=
hey're not usually more than three hours long.
I find it takes some experimenting with spectrogram parameters to make call=
s visible, and also the horizontal and vertical scales.
I generally view a minute or two per screen, and Audacity lets you move a p=
age at a time with Page Up and Page Down. I add comments to a label track w=
hen I find something interesting. I also prepopulate another label track wi=
th the actual times every minute (e.g. 6.00am, 6.01am, etc) so I can easily=
tell what time a call was made. (I've written an Audacity plugin for that,=
if anyone wants it.)
An advantage of viewing spectrograms is that if you find something interest=
ing, you can quickly scan again looking for fainter instances of that call =
you may have missed now that you know what it looks like.
If I had a 24 hour recording to work through I'd consider listening to, say=
, 15 minutes of each hour, and only looking at the rest if I find something=
interesting in those samples. If I had more recordings taking place while =
I was processing the backlog, I see no alternative to this unless I had hel=
p.
Another thing I do is to put the recordings on my phone (and more recently =
my iPad) so I can listen to them on the way to work on the train. I break t=
hem into one minute sections, named after the start time of each section, s=
o I can more easily tell where I'm up to and make notes about something I h=
eard and want to check more carefully at home. Audacity can use the time la=
bels I created to split and name the sections as it exports.
I'd like to be able to view spectrograms on the iPad, but I've found no app=
s that will display them. I've been experimenting with creating them as mov=
ies, which iPads are very good at displaying. The plan is to still break th=
em into small segments, perhaps 5 minutes long. I'd love to be able to make=
notes directly in the movies, and I'm hoping something like iMovie will al=
low that.
Peter Shute
> -----Original Message-----
> From:
> On Behalf Of klangstrand
> Sent: Monday, 8 April 2013 6:18 AM
> To:
> Subject: [Nature Recordists] Re: Reviewing long recordings
>
>
>
>
> Hi!
> My solution is spectral view. Most often I use Soundtrack
> Pro, or Audition. Audacity has it also, and is free.
> The spectral view easily shows when something "different"
> happens, that would otherwise be invisible in waveform, like
> high pitched things, that don=B4t carry alot of energy, respectively.
> You can also trim the view of noisefloor so that you see
> low-energy things happening aswell, in addition to choose
> frequency range. Thing sticks out pretty fast.
> After a while one gets a hunch of types of activity looking
> at the spectrum. Even pointing out different species. Every
> bird and animal has its distinct drawings.
> I get through hours of recordings pretty fast this way, if
> that=B4s what I need for the task at hand.
> Best
> -Anders
>
> --- In
> <naturerecordists%40yahoogroups.com> , "chrishails50"
> <> wrote:
> >
> > Dear all
> >
> > Related to my last question, I wonder if anyone has any
> great tricks for reviewing long duration recordings ?
> >
> > I have over the years amassed enough reasonable mics and
> machines to have at least two sets (and maybe a third) that
> can be left out unattended overnight. I would like to survey
> my local woods and forests and catch some of the owls that
> are out there that I have not yet recorded.
> >
> > But my question is how to review an 8-10 hour session
> efficiently ? In the past I have had them playing background
> whilst I do other tasks, but normally I can only spend maybe
> 2 hours doing that. I then moved on to scanning the waveform
> files (for night-time this works I think): I apply a 100%
> notch filter below 600Hz to get rid of passing planes and boy
> racers then scroll the waveform (I use Audition 3)and look
> for peaks that could be interesting sounds. But as I have
> just discovered even this takes a chunk of time if I have two
> machines running overnight.
> >
> > I know a real field guy would spend the night wandering the
> forest with his parabola, but I have a day job too.....has
> anyone else faced this ?
> >
> > Thanks for any tips or ideas.
> >
> > Chris
> > http://www.wildechoes.org
> >
>
>
>
>
>
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