I've posted a "noise only" sample to Soundcloud. I'll stop calling it hiss =
for now:
http://soundcloud.com/petershute/120202-01pcmm10silence
I haven't had time to take the recorder anywhere truly quiet to record a be=
tter sample, so this was done at home with doors and windows closed, sandwi=
ched between two cushions with a blanket over the top. I'm sure there's ple=
nty 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 bel=
ow 500Hz which might be noise from outside that I couldn't block. Very inte=
rested to hear opinions about the nature of the noise.
I also did a similar recording with the level turned right down. There was =
similar noise, but of much, much lower volume. I assume this proves it's no=
t 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 i=
nterested to know what others find wrong with it. The untouched recording f=
or comparison is at:
http://soundcloud.com/petershute/111229-03brandyck
Concerning my hearing, I took my audiologist's word that I've got little he=
aring above 8kHz, but I played with tone generation in audacity just now, a=
nd I can hear up to 15kHz, but I can't really quantify how well except that=
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. Inter=
estingly, at a level at which I can clearly hear 15000Hz, 15100 is just not=
there. I'm probably running into equipment limitations too.
Peter Shute
From: O=
n Behalf Of Avocet
Sent: Saturday, 11 February 2012 10:19 AM
To:
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
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