I don't know why we're seeing different things in the frequency analysis. P=
erhaps it's to do with the (Audacity) settings I used to do the analysis - =
I left them on the defaults, as I don't understand what they do.
They were:
- Algorithm: spectrum
- Function: Hanning window
- Size:512
- Axis: linear
I've just fiddled with the size parameter. If I change it to 128 then I see=
a much more detailed graph going all the way up to 21500Hz! This is from t=
he original wav file.
Apologies to those who had to record it from Soundcloud - I didn't realise =
the default was to prevent downloading. Thanks for taking the trouble, to t=
hose who did.
Peter Shute
From: O=
n Behalf Of hartogj
Sent: Sunday, 12 February 2012 6:44 AM
To:
Subject: [Nature Recordists] Re: M10 noise removal, was Sony PCM-M10 vs Zoo=
m H4n best for outdoor
Hi Peter,
I think David gave a good characterization of the noise in your samples.
I'm not sure why your frequency analysis shows it all below 9khz, because l=
ooking at it and listening to it with Audition 1.5 and apQualizr the record=
er/mic noise clearly extends to where the mp3 chops off around 14k. The hig=
h point in the noise appears to me centered around 4k at the top of a wide =
bulge that tapers off to several dB less above 10k.
Still, the background ambiance in your nature recording example blends with=
and somewhat masks the 4k noise, so to my ears the >8k noise is still what=
sounds the most noticeable.
Consider natural background sounds that can mask that <8k noise. Some wind =
in the trees or water flowing somewhere nearby can make all the difference =
with fairly noisy mics like these.
Here is an old example from my Sound Journal. Using Sure wl-183(~20 dB self=
-noise) microphones mounted to a tree, thanks to the wind in the pines, a s=
mall nearby stream, and post eq on the high hiss(>8k?) this one sounds pret=
ty good - to my ears anyway.
http://rockscallop.org/ear/jh-060529_fry-dawn02.mp3
John Hartog
rockscallop.org
--- In <naturerecordists%40yahoogrou=
ps.com>, Peter Shute <> wrote:
>
> I've posted a "noise only" sample to Soundcloud. I'll stop calling it his=
s for now:
> http://soundcloud.com/petershute/120202-01pcmm10silence
>
> I haven't had time to take the recorder anywhere truly quiet to record a =
better sample, so this was done at home with doors and windows closed, sand=
wiched between two cushions with a blanket over the top. I'm sure there's p=
lenty of sound from outside in the recording, but at least I've reduced it.
>
> The spectrum analysis in Audacity says it's all below 9kHz, with a peak b=
elow 500Hz which might be noise from outside that I couldn't block. Very in=
terested to hear opinions about the nature of the noise.
>
> I also did a similar recording with the level turned right down. There wa=
s similar noise, but of much, much lower volume. I assume this proves it's =
not preamp noise?
>
> I've also uploaded the latest attempt at reducing the noise:
> http://soundcloud.com/petershute/111229-03nr5
>
> With 30dB reduction, I've not been very gentle with the recording, so I'm=
interested to know what others find wrong with it. The untouched recording=
for comparison is at:
> http://soundcloud.com/petershute/111229-03brandyck
>
> Concerning my hearing, I took my audiologist's word that I've got little =
hearing above 8kHz, but I played with tone generation in audacity just now,=
and I can hear up to 15kHz, but I can't really quantify how well except th=
at it's nowhere near as good as at 8. I note that she didn't test above 8.
>
> Perhaps I'm playing it back louder than she would have in a test too. Int=
erestingly, at a level at which I can clearly hear 15000Hz, 15100 is just n=
ot there. I'm probably running into equipment limitations too.
>
> Peter Shute
>
> ________________________________
> From: <naturerecordists%40yahoogro=
ups.com> <naturerecordists%40yahoog=
roups.com>] On Behalf Of Avocet
> Sent: Saturday, 11 February 2012 10:19 AM
> To: <naturerecordists%40yahoogroup=
s.com>
> Subject: Re: [Nature Recordists] Re: M10 noise removal, was Sony PCM-M10 =
vs Zoom H4n best for outdoor
>
>
>
> > Peter mentioned on his Soundcloud example, the hiss he was concerned
> > with was mostly below 5kHz. To my own ears the problematic
> > microphone hiss noise in that recording was most prominent from 8 to
> > 10 kHz.
>
> John,
>
> In my previous email I indirectly defined "hiss" in my HPF
> specification as being 4KHz and above, in other words the top two
> octaves. "Thermal" (root f) mic hiss goes right up as high as you
> record and to my ears anyway sounds different. The bottom end noise
> (the bottom four octaves?) is "rumble" but I can't think of a
> universal name for mid range noise except "mid range noise". :-)
>
> I'll back you up on annoying hiss being 8 to 10 Khz and this is
> recognised in the "468" weighting for background noise measurements.
>
> BTW at my fairly advanced age of 71 my own frequency response still
> goes from 10Hz to 12KHz which is not bad. That's still over 10
> octaves.
>
> David
>
> David Brinicombe
> North Devon, UK
> Cogito cogito ergo cogito sum - Ambrose Bierce
>
|