Thanks for all the responses everyone, I'm just working my way through them=
now.
I tried looking at the spectrogram first, but I found the low frequencies a=
bit hard to interpret on it, unlike bird calls, which make nice patterns.
I was looking for bright spots towards the bottom of the display, but birds=
fluttering past create spots like that too. Later in the recording the win=
d increases, and then it's even harder to pick out the right ones. I guess =
I'm looking for a short, sudden increase around 2-300Hz, and while I can fi=
nd occurences of that range, I found it hard to spot short occurences vs lo=
nger ones that generally turned out to be something else, and I find it har=
d to tell how sudden the increase it without looking at the waveform.
Peter Shute
> -----Original Message-----
> From:
> On Behalf Of Danny
> Sent: Tuesday, 6 November 2012 7:26 AM
> To:
> Subject: [Nature Recordists] Re: Background thumps in recording
>
>
>
> The first one sounds like a distant car door to me. Though it
> could be something else.
>
> In any case I think the quickest way to spot them without
> listening to the whole recording is to look at the recording
> spectrogram and the very low frequency energy will show up
> strongly at the bottom of the frequency spectrum. The free
> software Audicity has a spectrogram mode that is pretty good.
>
> After that you could use software such as Izotope RX Spectral
> Repair to repair the noises. I have had success with these
> types of sounds in the past using Spectral Repair. It can
> erase them with no audible artifacts if you use it right.
>
> --- In
> <naturerecordists%40yahoogroups.com> , Peter Shute
> <> wrote:
> >
> > Well, that was smart. I forgot to include the link to a
> sample of the recording:
> > http://soundcloud.com/petershute/dawn-chorus-pheenys-track
> >
> > I've put comments where all the thumps are in that one
> minute sample.
> >
> > Peter Shute
> >
> > ________________________________
> > From:
> > <naturerecordists%40yahoogroups.com>
> >
> > <naturerecordists%40yahoogroups.com> ] On Behalf Of
> Peter Shute
> >
> > Sent: Tuesday, 6 November 2012 5:52 AM
> > To:
> > <naturerecordists%40yahoogroups.com>
> > Subject: [Nature Recordists] Background thumps in recording
> >
> >
> >
> > I recentlly made some recordings in Murray Sunset National
> Park, in north west Victoria, Australia. It was, I thought, a
> very quiet place in the mornings before the wind started,
> apart from the birds.
> >
> > But in one recording, there is a thumping noise at random
> intervals, right through the two hour recording, which starts
> just before sunrise. Could I please have some opinions on
> what these noises might be?
> >
> > At first I thought they were a car door being slammed - we
> were camped about 300m away, just over the hill - but there
> are far too many of them. Gunshots? Not allowed in the park,
> and the nearest farms are over 10km away, although it's still
> possible, as there are feral goats in the park.
> >
> > I'd also like to know if there's a good way of finding all
> of these in the recording without having to listen to it. I
> can only hear them if I use headphones, and if there's no
> background noise in the room, so it took me a while to find
> as many as I have.
> >
> > After I'd found a few just by listening, I used EQ to
> reduce everything above 400Hz and increase everything below
> 200Hz. This makes them way more obvious to the ear, and I can
> spot most on the waveform, but it's not very pleasant to
> listen to. It also makes the sound of wingbeats sound
> similar, so I made a few mistakes.
> >
> > Could there be an automated way of finding them all, or
> making them reliably more obvious on the waveform? I use Audacity.
> >
> > Peter Shute
> >
> >
> >
> >
> >
>
>
>
>
>
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