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Re: ME67 handling noise samples uploaded

Subject: Re: ME67 handling noise samples uploaded
From: "Avocet" madl74
Date: Sat Nov 6, 2010 7:45 pm ((PDT))
Stephen,

Here's my notes of your recordings:

noise1gain10
Classic wind noise.
I used a very steep 200Hz HPF between 04:00 and 06:00 and the
recording was "useable". Suggest lowering recording level by 20dB or
more to avoid LF "blocking".

noise2gain10hpf
Power spectrum showed bass step lift below 300HZ and rising steeply
below that. Constructed a corrective filter in "Audacity -
Equalisation" and the wind noise went. Remaining noise has a
characteristic frequency and sounds like handling noise.

noise3gain5
LF booming handling noise, most likely a resonance on the mic mount or
windgag. I couldn't easily isolate the frequency, which was in the
lower voice range but it was greatly reduced by a 200Hz 6dB per octave
HPF (Equalisation again)

recording1
more LF booming. Power spectrum (Audacity - Analyse - Plot Spectrum)
showed call (what was it?) between 05:00 and 06:00 which was above 200
Hz so the same 200 Hz HPF cleaned it up. That suggests handling 0noise
in the 100Hz region.

recording2
Sounds great, but I don't know the species. Spectrum showed noise
mainly below 100Hz this time so 80Hz HPF removed most of the handling?
noise except for a peak near or at overload at around 08:00. 10db
lower would have avoided this. Spectrum of noise sample from 15:50 to
16:00 shows bird around 3500Hz and 5600Hz and noise at those
frequencies about 30dBs below peak which is at about -24dB, or -54dB
give or take. With recording noise at say -80dB, that's still over 20
dB above system noise. Suggest recording 10dB lower.

I recommend chasing handling noise. Make a mental recording of the
booming I'm talking about then with a quiet background tap around the
mic and mount and the cable to see if you can trace the source. You're
lookning for a doomph sound. It could be well coming down the cable.

I've used an equivalent mic the MKH 816 a lot and still use one. The
general rule is the more directional, the more a mic is prone to wind
and handling noise. I use the old type of Rycote mount which uses hat
elastic and the mic has to flop about quite lot for it to work, about
five flops per second or slower. (You can buy Rycote lyre mounts as
spares.)

I've made up short cables - just enough to use handheld - using
"fleximic" cable which is rubbery and transmits less noise. I've
doubled it back on the mic plug end to form a loop and anchored it to
the mount, all still floppy.

I wrote about windsocks before, and how they are a high pass filter.
If they are made of a close weave fabric, like the Rycote "yeti", they
cut the bass before it gets to the mic. The Rycote plastic windgag has
a resonant "doomph" frequency so I use a mic stand for quiet
recordings. Otherwise I uses a "boomswingers arm", leaving the muscles
slack as arm muscles can cause quite a lot of handling noise. My
assistants never got away with using stiff arms. :-)

David

David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce







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