[Peter A. Stoll[_2_]]

I mostly read here, and have for years. Now I seek help with a recent
recording problem. I've been recording with the same equipment and very
similar setup once every few months for some time, and this artifact
problem is new, so I think either I fouled up something in setup, the
venue had a novel (to me) problem, or some piece of equipment is in a
degraded state.

I first noticed the problem almost by feeling it rather than hearing it--
irregular and intermittent thuds or flutters felt in the ear when
auditioning the recording on headphones afterwords. It is not audibly
present for minutes on end, but then for a few seconds will have strong
effect. The two channels are not showing the same waveform, though often
the second channel will have detectable artifact within a couple of
seconds of the one I noticed first.

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

If you are interested in helping, but don't wish to follow that link,
here are a few more details:

Ensemble: 20-voice chorus, unaccompanied
Microphone position: near ORTF, up on 8 feet of stand, about 25 feet from
the singers.
Microphones: Schoeps CMC6 MK41 capsules
Cables were duct taped about every one to two feet down stand
Recorder: Sound Devices 722, running on internal battery.
Nothing else (no mixer, ...)

Artifact frequency content and energy (based on spectrum comparison)
rises above hall noise floor at about 75 Hz--approximately linear rise
from there down to 30 Hz, at which point it is about 35dB above room
tone, and remains over 20 dB over room tone to below 5 Hz. Not tonal or
spiky at all on the spectrum.

Any advice on what might have happened, and what I need to do differently
to avoid getting it in the future would be most welcome.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. It seems to help quite a bit, but may be
doing harm I've not yet noticed. While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

Thanks

[Scott Dorsey]

Peter A. Stoll wrote:

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

Sounds like wind noise to me. Where is the closest HVAC vent? Are there
any candles in the hall? Are you near a hot lighting fixture that will be
moving air around?

I suggest trying the Olsen Audio Group WindTech screens, which are only about
$20 and pretty acoustically transparent. They are not as effective as the
Rycote Baby Ball Gag but they are much cheaper and still very good.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. It seems to help quite a bit, but may be
doing harm I've not yet noticed. While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

If you don't have anything below 70 Hz, like a pipe organ or bassoon, I
wouldn't worry about it in this case. But I'd consider using a wind screen
in that venue in the future. Sometimes moving the mikes a few inches fixes
everything, sometimes not.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Peter A. Stoll[_2_]]

(Scott Dorsey) wrote in
:

Peter A. Stoll wrote:

Sounds like wind noise to me. Where is the closest HVAC vent? Are
there any candles in the hall? Are you near a hot lighting fixture
that will be moving air around?

It was a church sanctuary, and the mike stand was in the first pew--so at
least thirty feet from any vent. They told us the sanctuary refrigerated
air was off--and I believe it, as it was a retrofit job using much too
small existing ducting, which when run during rehearsal generated a
painfully cold breeze at my standing position (I sing in the group as
well as recording).

But there seems to have been evaporative cooling running elsewhere in the
building (this early in the season, you can smell the recently replaced
aspen pads), and with large open doors to the sanctuary, and the very
large volume of air moved by such installations, I'd imagine there may
have been low velocity air currents from that source.

I suggest trying the Olsen Audio Group WindTech screens, which are
only about $20 and pretty acoustically transparent. They are not as
effective as the Rycote Baby Ball Gag but they are much cheaper and
still very good.

Thanks for the practical suggestion--I'll follow up on this.

If you don't have anything below 70 Hz, like a pipe organ or bassoon,
I wouldn't worry about it in this case. But I'd consider using a wind
screen in that venue in the future. Sometimes moving the mikes a few
inches fixes everything, sometimes not.

Although in my comparison five second sample the one day seemed affected
and the other not, I actually had trouble both days, The actual sites
were opposite sides of the main aisle (they moved the piano from stage
left to stage right between the two performances, so I made the
reciprocal move) and probably about ten feet apart.

--scott

I confess I posted this also on the Sound Devices site (there I was
hoping the highest chance of someone recognizing a known SD degradation
mode--here I was hoping more for advice on setup error or venue
problems). The one person responding there so far also pointed to air
current problems and suggested "a foam windscreen".

Thanks for the advice.

Peter A. Stoll
former microprocessor person

[Mark]

On May 24, 2:47*pm, "Peter A. Stoll"
wrote:
I mostly read here, and have for years. *Now I seek help with a recent
recording problem. *I've been recording with the same equipment and very
similar setup once every few months for some time, and this artifact
problem is new, so I think either I fouled up something in setup, the
venue had a novel (to me) problem, or some piece of equipment is in a
degraded state.

I first noticed the problem almost by feeling it rather than hearing it--
irregular and intermittent thuds or flutters felt in the ear when
auditioning the recording on headphones afterwords. *It is not audibly
present for minutes on end, but then for a few seconds will have strong
effect. *The two channels are not showing the same waveform, though often
the second channel will have detectable artifact within a couple of
seconds of the one I noticed first.

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. *I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

If you are interested in helping, but don't wish to follow that link,
here are a few more details:

Ensemble: 20-voice chorus, unaccompanied
Microphone position: near ORTF, up on 8 feet of stand, about 25 feet from
the singers.
Microphones: Schoeps CMC6 MK41 capsules
Cables were duct taped about every one to two feet down stand
Recorder: Sound Devices 722, running on internal battery.
Nothing else (no mixer, ...)

Artifact frequency content and energy (based on spectrum comparison)
rises above hall noise floor at about 75 Hz--approximately linear rise
from there down to 30 Hz, at which point it is about 35dB above room
tone, and remains over 20 dB over room tone to below 5 Hz. *Not tonal or
spiky at all on the spectrum.

Any advice on what might have happened, and what I need to do differently
to avoid getting it in the future would be most welcome.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. *It seems to help quite a bit, but may be
doing harm I've not yet noticed. *While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

Thanks

could it be low freq floor noise conducted through the mic stands?

someone in the audience or performers with a heavy foot?

Mark

[Mark]

On May 24, 4:47*pm, Mark wrote:
On May 24, 2:47*pm, "Peter A. Stoll"
wrote:





I mostly read here, and have for years. *Now I seek help with a recent
recording problem. *I've been recording with the same equipment and very
similar setup once every few months for some time, and this artifact
problem is new, so I think either I fouled up something in setup, the
venue had a novel (to me) problem, or some piece of equipment is in a
degraded state.

I first noticed the problem almost by feeling it rather than hearing it--
irregular and intermittent thuds or flutters felt in the ear when
auditioning the recording on headphones afterwords. *It is not audibly
present for minutes on end, but then for a few seconds will have strong
effect. *The two channels are not showing the same waveform, though often
the second channel will have detectable artifact within a couple of
seconds of the one I noticed first.

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. *I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

If you are interested in helping, but don't wish to follow that link,
here are a few more details:

Ensemble: 20-voice chorus, unaccompanied
Microphone position: near ORTF, up on 8 feet of stand, about 25 feet from
the singers.
Microphones: Schoeps CMC6 MK41 capsules
Cables were duct taped about every one to two feet down stand
Recorder: Sound Devices 722, running on internal battery.
Nothing else (no mixer, ...)

Artifact frequency content and energy (based on spectrum comparison)
rises above hall noise floor at about 75 Hz--approximately linear rise
from there down to 30 Hz, at which point it is about 35dB above room
tone, and remains over 20 dB over room tone to below 5 Hz. *Not tonal or
spiky at all on the spectrum.

Any advice on what might have happened, and what I need to do differently
to avoid getting it in the future would be most welcome.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. *It seems to help quite a bit, but may be
doing harm I've not yet noticed. *While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

Thanks

could it be low freq floor noise conducted through the mic stands?

someone in the audience or performers with a heavy foot?

Mark- Hide quoted text -

- Show quoted text -

also I forgot to suggest, since the noise is only occasional, can you
use aggresive high pass filtering with DAW automation so that you
apply the filter only when needed...

Mark

[Peter A. Stoll[_2_]]

Mark wrote in
:

On May 24, 2:47*pm, "Peter A. Stoll"
wrote:

could it be low freq floor noise conducted through the mic stands?

someone in the audience or performers with a heavy foot?

Mark

The microphone pair was on a single stand. I don't see how stand conducted
very low frequency noise from the floor could differ so dramatically from
channel to channel for a pretty closely spaced pair on the same stand.

The sound seemed unlike any feet I've heard (which is plenty), and the
shape of the spectral content would seem hard to obtain in that way.

Just my opinion--I'd not be asking for help here were I sure of much of
anything.

[Nono]

On 24 mei, 20:47, "Peter A. Stoll"
wrote:
I mostly read here, and have for years. *Now I seek help with a recent
recording problem. *I've been recording with the same equipment and very
similar setup once every few months for some time, and this artifact
problem is new, so I think either I fouled up something in setup, the
venue had a novel (to me) problem, or some piece of equipment is in a
degraded state.

I first noticed the problem almost by feeling it rather than hearing it--
irregular and intermittent thuds or flutters felt in the ear when
auditioning the recording on headphones afterwords. *It is not audibly
present for minutes on end, but then for a few seconds will have strong
effect. *The two channels are not showing the same waveform, though often
the second channel will have detectable artifact within a couple of
seconds of the one I noticed first.

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. *I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

If you are interested in helping, but don't wish to follow that link,
here are a few more details:

Ensemble: 20-voice chorus, unaccompanied
Microphone position: near ORTF, up on 8 feet of stand, about 25 feet from
the singers.
Microphones: Schoeps CMC6 MK41 capsules
Cables were duct taped about every one to two feet down stand
Recorder: Sound Devices 722, running on internal battery.
Nothing else (no mixer, ...)

Artifact frequency content and energy (based on spectrum comparison)
rises above hall noise floor at about 75 Hz--approximately linear rise
from there down to 30 Hz, at which point it is about 35dB above room
tone, and remains over 20 dB over room tone to below 5 Hz. *Not tonal or
spiky at all on the spectrum.

Any advice on what might have happened, and what I need to do differently
to avoid getting it in the future would be most welcome.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. *It seems to help quite a bit, but may be
doing harm I've not yet noticed. *While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

Thanks



I haven't been able to listen to the audio samples, but I've had a
little problem with my console some years ago like faint thuds that
sounded like little explotions or miniature storms goin on through my
audio occasionally. For some periods the problem would appear and then
it would be fine for a couple of months etc.
Then Marco Eijkeboom of service center DSA Apeldoorn pointed me out
that the clips used to attach the power cables of the power supply to
the master PCB of the console were the problem.
He advised me to cut these clips off and instead solder the wires to
the PCB. First I was reluctant to do so, because soldering the wires
meant that whenever I had to take my master modules out I would have
to solder the wires off and on instead of the convenience of just
pulling these clips off and back on again.
Besides, even though I trusted Marco's expertise and that I did notice
that playing with these wires made these rumbling sounds, I couldn't
really understand how soldering would solve the problem.
And I still do not understand, but fact is that from the day that I
soldered the wires some years ago, I haven't had any issues with
mysterious popping sounds whatsoever.

In your case, you might check the cables of the internal battery of
your recorder and how they're attached to the PCB of the recorder.
Apparently if the wires for the power supply are not steadily and
firmly attached, they can give rumbling, popping noises in the audio.

Should this not be the cause, I hope that you do find the problem
soon.

Best regards,
Norman.

[Don Pearce[_3_]]

On Mon, 24 May 2010 13:47:14 -0500, "Peter A. Stoll"
wrote:

I mostly read here, and have for years. Now I seek help with a recent
recording problem. I've been recording with the same equipment and very
similar setup once every few months for some time, and this artifact
problem is new, so I think either I fouled up something in setup, the
venue had a novel (to me) problem, or some piece of equipment is in a
degraded state.

I first noticed the problem almost by feeling it rather than hearing it--
irregular and intermittent thuds or flutters felt in the ear when
auditioning the recording on headphones afterwords. It is not audibly
present for minutes on end, but then for a few seconds will have strong
effect. The two channels are not showing the same waveform, though often
the second channel will have detectable artifact within a couple of
seconds of the one I noticed first.

As I recorded the same concert by the same performers in the same venue
with the same equipment, setup, and settings on two successive days I
could make very close comparisons of two five second stretches of the
same music--one heavily affected and one not. I've prepared a web page
showing waveforms, spectra, and providing the actual .wav files for this
comparison, in hopes of getting advice here.

http://home.comcast.net/~archae86/thud1.html

If you are interested in helping, but don't wish to follow that link,
here are a few more details:

Ensemble: 20-voice chorus, unaccompanied
Microphone position: near ORTF, up on 8 feet of stand, about 25 feet from
the singers.
Microphones: Schoeps CMC6 MK41 capsules
Cables were duct taped about every one to two feet down stand
Recorder: Sound Devices 722, running on internal battery.
Nothing else (no mixer, ...)

Artifact frequency content and energy (based on spectrum comparison)
rises above hall noise floor at about 75 Hz--approximately linear rise
from there down to 30 Hz, at which point it is about 35dB above room
tone, and remains over 20 dB over room tone to below 5 Hz. Not tonal or
spiky at all on the spectrum.

Any advice on what might have happened, and what I need to do differently
to avoid getting it in the future would be most welcome.

My initial try at cleanup was a 6th order Butterworth high pass filter
with 70 Hz corner frequency. It seems to help quite a bit, but may be
doing harm I've not yet noticed. While my main desire is to avoid
capturing sound like this in the future, any tips on cleanup would also
be most welcome.

Thanks

Yes it is certainly moving air - fairly slow movement - that is doing
that. You can quite safely apply the low pass filter as you have to
remove it. In fact it is no bad idea to do this routinely provided you
know the lowest instrument frequency you are going to record. You can
get rid of a whole load of potential nasties this way - nasties that
may only be noticed by someone with a decent subwoofer.

It is best stopped at source though, and for that you need a
windscreen. A foam screen on the mic won't do it. Distance is the key
- the screen works better the farther it is from the diaphragm, so a
large one is better - this is a fixed mic so it should be no problem.

Another way is to keep the mic out of the air current. A wet finger
test should tell you where the air is still. Warm wet finger = still
air, cold wet finger = moving air.

d

[Scott Dorsey]

Don Pearce wrote:
It is best stopped at source though, and for that you need a
windscreen. A foam screen on the mic won't do it. Distance is the key
- the screen works better the farther it is from the diaphragm, so a
large one is better - this is a fixed mic so it should be no problem.

Another way is to keep the mic out of the air current. A wet finger
test should tell you where the air is still. Warm wet finger = still
air, cold wet finger = moving air.

It's not always that easy. I did a gig a decade or so ago using B&K
measurement mikes on a small baroque orchestra for a live concert. The
run-through in the afternoon was great. Then, for the concert, they
lit candles all over the ballroom.... my meters were jumping up and
down 20 dB but I couldn't hear a damn thing in the headphones.... I was
greatly alarmed until I figured out what was going on. Wound up having
to high-pass at 15 Hz and everything was fine....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Peter A. Stoll[_2_]]

"Peter A. Stoll" wrote in
. 97.131:

(Scott Dorsey) wrote in
:
Sounds like wind noise to me.
snip
I suggest trying the Olsen Audio Group WindTech screens

Considering that at this point four experienced people have confidently
diagnosed air current noise (including Jon of SD) and bearing in mind
concerns about the adequacy of thin foam screens for this mission (and the
fact that I already have thin screens which came with the Schoeps kit,
somewhere...) I've ordered a pair of WindTech US-2 windscreens. Foam they
are, but thin they are not (3 3/8 inch external diameter).

From the pictures they look rather less attention grabbing than the Rycote
BBG. I won't even imagine the bystander reaction to the Windjammer (looks
like a Tribble to me).

Peter A. Stoll
former microprocessor person

[Arny Krueger]

"Peter A. Stoll" wrote in
message
. 97.131
I mostly read here, and have for years. Now I seek help
with a recent recording problem. I've been recording
with the same equipment and very similar setup once every
few months for some time, and this artifact problem is
new, so I think either I fouled up something in setup,
the venue had a novel (to me) problem, or some piece of
equipment is in a degraded state.

I first noticed the problem almost by feeling it rather
than hearing it-- irregular and intermittent thuds or
flutters felt in the ear when auditioning the recording
on headphones afterwords. It is not audibly present for
minutes on end, but then for a few seconds will have
strong effect. The two channels are not showing the same
waveform, though often the second channel will have
detectable artifact within a couple of seconds of the one
I noticed first.

These look and sound like things that I have been able to remove from my
recordings by mounting my microphones in shock mounts.

[Arny Krueger]

"Peter A. Stoll" wrote in
message
7.131
Mark wrote in
:

On May 24, 2:47 pm, "Peter A. Stoll"
wrote:

could it be low freq floor noise conducted through the
mic stands?

someone in the audience or performers with a heavy foot?

The microphone pair was on a single stand. I don't see
how stand conducted very low frequency noise from the
floor could differ so dramatically from channel to
channel for a pretty closely spaced pair on the same
stand.

Agreed. Unfortunately, I found this post after I made a similar comment as
Mark.

The sound seemed unlike any feet I've heard (which is
plenty), and the shape of the spectral content would seem
hard to obtain in that way.

Noises like this can be all over the map depending on the exact
circumstances.

Just my opinion--I'd not be asking for help here were I
sure of much of anything.

The sound could easily be wind noise - it almost sounds like someone
breathing heavily into a mic. How close are the mics to each other and the
group?

[Peter A. Stoll[_2_]]

"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message

These look and sound like things that I have been able to remove from my
recordings by mounting my microphones in shock mounts.

At the time my microphones were in the modest shock mounts Schoeps supplies
as part of the US kits. Sort of black fabric-covered elastic in a cat's
cradle type arrangement. Not so large as the really big one's I've seen.
I can't speak to how effective they are.

[Peter A. Stoll[_2_]]

"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message
7.131

The sound could easily be wind noise - it almost sounds like someone
breathing heavily into a mic. How close are the mics to each other
and the group?

Microphones were on a single 8 foot high stand, with the business ends
being seven or 8 inches from each other, and 20 to 25 feet from the group.
I think we can safely exclude human breathing. Still it is good for me to
know that it can sound something like that, which I never would've guessed.
Thanks.

[Arny Krueger]

"Peter A. Stoll" wrote in
message
. 97.131
"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message
7.131

The sound could easily be wind noise - it almost sounds
like someone breathing heavily into a mic. How close
are the mics to each other and the group?

Microphones were on a single 8 foot high stand, with the
business ends being seven or 8 inches from each other,
and 20 to 25 feet from the group. I think we can safely
exclude human breathing. Still it is good for me to know
that it can sound something like that, which I never
would've guessed. Thanks.

I figured as much about mic location, as I use a NT4 in a similar
configuration for recording choir festivals. I've never had problems of the
kind you demonstrate with your otherwise really nice choir recordings.

I find it hard to believe that air turbulence would be as different among
the channels as the noises in your recordings, with mics only a few inches
apart.

But, my omniscience module is permantly broken! ;-)

There are no doubt many differences among our venues. I do sometimes have
situations where HVAC noise intrudes. Sometimes mechanical noise, pretty
steady around 20-30 Hz, and sometimes a steady rushing sound due to air
turbulence. Never bursts of the kind you had.

[Arny Krueger]

"Peter A. Stoll" wrote in
message
. 97.131
"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message

These look and sound like things that I have been able
to remove from my recordings by mounting my microphones
in shock mounts.

At the time my microphones were in the modest shock
mounts Schoeps supplies as part of the US kits. Sort of
black fabric-covered elastic in a cat's cradle type
arrangement. Not so large as the really big one's I've
seen. I can't speak to how effective they are.

IME it doesn't take a lot of shock mount to be far more effective than
nothing!

Mechanical noise being transmitted up the stand seems to be far less likely
than I might have thought.

The remaining possibility is electronic. What happens if you leave
everything hooked up as it is, but swap the location of the mics L&R?

You can always restore normal L&R later on.

[Peter A. Stoll[_2_]]

"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message
. 97.131

I find it hard to believe that air turbulence would be as different
among the channels as the noises in your recordings, with mics only a
few inches apart.

The five seconds I selected for study had the effect much more in left that
right--and not at all synchronous. But I don't think that across the full
set of troubles there was a left to right inbalance. I don't know how much
of the difference between the two would need to be "wind shear" (local
difference in velocity seven inches apart), vs possibly just being a
difference in the way the microphone reacts to impinging air based on
angle. My "sort of ORTF" version that day had about a 70 degree angle
between the mics, so they were would not be seeing the same relative wind
even were there no wind shear between them at all.

There are no doubt many differences among our venues. I do sometimes
have situations where HVAC noise intrudes. Sometimes mechanical noise,
pretty steady around 20-30 Hz.

One church I otherwise like has always had a peak around 47 Hz. I assume
it is rotating machinery somewhere. It is not very high, and I've never
heard it, either in the hall or on the recordings, but there it always is
in the spectrum. I'm more troubled by the multiples of 60 Hz I see,
especially in another church were some of the overhead lighting at the back
of the sanctuary is !@#$!@#$ CFL, and plenty loud enough to see in the
spectrum, hear in the hall, and hear on the recording.

Peter A. Stoll
former microprocessor person

[Peter A. Stoll[_2_]]

"Arny Krueger" wrote in
news
"Peter A. Stoll" wrote in
message
. 97.131
"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in
message


The remaining possibility is electronic.

I made another recording on the first of the two days with trouble in
another venue, with none of this. Still, the unit could have developed a
problem that day.

As I have no near term recording for real in prospect, I'm toying with the
idea of just running the equipment for a couple of hours in my living room
on a quiet day to see if I get it. Then I might try some trial intentional
movement, just to get a subjective impression of what degree of stand
movement through the air gives this sort of effect (and to what degree the
two mics "hear" it differently. As my motions will doubtless not emulate
the actual currents that day, I don't expect exact replication. But at
least I'll have some basis of understanding, and perhaps a means to get a
sense of how much my existing and new wind screens help.

[philicorda[_9_]]

On Tue, 25 May 2010 07:21:08 -0500, Peter A. Stoll wrote:

"Arny Krueger" wrote in
:

"Peter A. Stoll" wrote in message
7.131

The sound could easily be wind noise - it almost sounds like someone
breathing heavily into a mic. How close are the mics to each other and
the group?

Microphones were on a single 8 foot high stand, with the business ends
being seven or 8 inches from each other, and 20 to 25 feet from the
group. I think we can safely exclude human breathing. Still it is good
for me to know that it can sound something like that, which I never
would've guessed. Thanks.

Is it a boom stand with a long arm? I had a problem once where the end of
the boom was occasionally wobbling just about 1/2 a cm or so, and this
was enough to cause some wind noise that looked like weird low frequency
flutter. It also would often be on just one channel. The mics were two
Rode NT5 in XY format.

I had the stereo pair on the end of a long boom, and it did not look like
the mics were moving. I tried putting some extra foam in the shock mount
mic clips, but it did not do anything. When I put up another couple of
stands to brace the boom, then the noise stopped.

This was with a rock band playing in a large room with a floating floor.
I think what was happening was the the vibrations from the drummer were
going through the floor, up the mic stand, and then the boom arm was
resonating at a much lower frequency, much too low to be stopped by the
shock mounts.

It must have been describing small circles at the end of the boom, so
depending on the velocity and angle, it would affect only one of the mics,
as the other mic would be offset 90 degrees and not get so much wind.

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.

[Peter A. Stoll[_2_]]

philicorda wrote in
:

On Tue, 25 May 2010 07:21:08 -0500, Peter A. Stoll wrote:


Is it a boom stand with a long arm?

The stand is a base with an short arm mounted on it. I wanted the total to
be easily carried in one hand, and I did not orginally foresee leaving the
arm installed, so the arm in particular is not especially sturdy. However
in this case, as almost always, the whole thing was standing straight up,
so less of a chance for some kinds of motion to build up.

Still, the whole setup has a lot more "give" than I imagine any pro would
use, so motion in it is a possible problem. I don't want to switch to a
seriously heavy, harder to carry, setup, so I guess for the moment I'm
going to hope that a serious wind screen would help that problem, if it
arose.

[Tom McCreadie]

On Tue, 25 May 2010 10:09:49 -0400, "Arny Krueger"
wrote:


IME it doesn't take a lot of shock mount to be far more effective than
nothing!

Mechanical noise being transmitted up the stand seems to be far less likely
than I might have thought.


I've also encountered this dull thudding in conditions very similar to
Peter's - 25 piece vocal ensembles in churches, with Schoeps Mk4 & Mk8's
in ORTF or MS, on 12 ft Manfrotto stands, without shockmounts

The problem - in same venues - was much less prevalent when I could hang
the mics up, and exacerbated when the stands were close to the audience
members, or on a wooden floor, so I'm inclined to attribute my issues
mainly to stand-borne vibrations and resonances. Fortunately, I can fly
for the majority of my recordings.

Heavy weights on the mic stand bases, and rigid foam under the legs,
made little difference. I'm contemplating the Rycote lyre mounts that
have been getting favourable mentions.
--
Tom McCreadie

Live at The London Palindrome - ABBA

[Peter Larsen[_3_]]

Peter A. Stoll wrote:

The microphone pair was on a single stand. I don't see how stand
conducted very low frequency noise from the floor could differ so
dramatically from channel to channel for a pretty closely spaced pair
on the same stand.

My first guess is cable noise, the next air convection, but the latter
should be strongly augmented at the mic capsule resonance. Before
listening/analyzing my guess is that the cause of the problem is that the
mic cables were taped to the stand.

The sound seemed unlike any feet I've heard (which is plenty), and the
shape of the spectral content would seem hard to obtain in that way.

Based on the spectral difference between channels the above remains my
opinion, now where ARE those M50's .... yessir, mechanical noise, it only
makes sense that it is cable banging on the mic stand transmitting the noise
to a mic that is not designed to isolate cable noise.

Just my opinion--I'd not be asking for help here were I sure of much

Tie or otherwise secure the cables to the cross-bar so as to avoid pull on
the mics, and rotate the mic stand tube a turn while raising it, it simpler,
faster and better.

Get off of the room centerline, the setup axis for mic pair and choir needs
to be offset by a foot.

Kind regards

Peter Larsen

[Peter A. Stoll[_2_]]

"Peter Larsen" wrote in
k:

Peter A. Stoll wrote:

Just my opinion--I'd not be asking for help here were I sure of much

Tie or otherwise secure the cables to the cross-bar so as to avoid
pull on the mics, and rotate the mic stand tube a turn while raising
it, it simpler, faster and better.

The setup I had curved the cables coming out of the back of the mics around
180 degrees and taped them to the microphone bar--I'd think there was some
appreciable isolation from disturbance further down the cable, but not
completely so, of course. After that the curved 90 to head on down the
stand, taped once to each of the four stand segments. With segments that
short, a deliberately induced motion damps very quickly. With full length
free, or even half, the damping times are many, many times longer. I'd not
heard of your twist method before--interesting.

Get off of the room centerline, the setup axis for mic pair and choir
needs to be offset by a foot.

I pretty much don't use the room centerline--my venues are nearly all
churches, which puts the centerline dead in the center aisle--a walking
obstruction to audience, and a collision worry for me. So, not thinking
there to be the sonic advantage you suggest, I've gotten the habit of
tucking it just far enough inside a pew to avoid the casual elbow.

This particular venue had a slightly odd first pew arrangement, and as a
result I was probably about 5 feet off centerline for both performances.

Kind regards

Peter Larsen

Thanks for the advice.
Peter A. Stoll

[Arkansan Raider]

philicorda wrote:

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.


Mmmkay, so like, why would a stage box be wearing shorts?

Heh.

Sorry, couldn't help myself.

That is all.


---Jeff

[philicorda[_9_]]

On Wed, 26 May 2010 18:36:16 -0500, Arkansan Raider wrote:

philicorda wrote:

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.


Mmmkay, so like, why would a stage box be wearing shorts?

You mean, you let them go completely naked?

Next you will be saying you don't cover up the piano legs. How unseemly.


Heh.

Sorry, couldn't help myself.

That is all.


---Jeff

[Arkansan Raider]

philicorda wrote:
On Wed, 26 May 2010 18:36:16 -0500, Arkansan Raider wrote:

philicorda wrote:

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.

Mmmkay, so like, why would a stage box be wearing shorts?

You mean, you let them go completely naked?

Next you will be saying you don't cover up the piano legs. How unseemly.

LOL

No seams. Mine all wear one-piece cloaks. Or maybe a saree or a kimono
if I'm outsourcing...


---Jeff

[Laurence Payne[_2_]]

On Thu, 27 May 2010 22:50:18 GMT, philicorda
wrote:

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.


Mmmkay, so like, why would a stage box be wearing shorts?

You mean, you let them go completely naked?

Next you will be saying you don't cover up the piano legs. How unseemly.

He said shorts IN it, not ON it. Obviously a few measures of whisky
have found their way into the equipment.

[Arkansan Raider]

Laurence Payne wrote:
On Thu, 27 May 2010 22:50:18 GMT, philicorda
wrote:

The only other time I've seen this kind of thing is with low phantom
volts caused by a stage box with some shorts in it.

Mmmkay, so like, why would a stage box be wearing shorts?
You mean, you let them go completely naked?

Next you will be saying you don't cover up the piano legs. How unseemly.

He said shorts IN it, not ON it. Obviously a few measures of whisky
have found their way into the equipment.

Fine, I won't share any with you.

Party pooper.



---Jeff

[Laurence Payne[_2_]]

On Fri, 28 May 2010 11:17:33 -0500, Arkansan Raider
wrote:

He said shorts IN it, not ON it. Obviously a few measures of whisky
have found their way into the equipment.

Fine, I won't share any with you.

Party pooper.

Eat my shorts.

[Arkansan Raider]

Laurence Payne wrote:
On Fri, 28 May 2010 11:17:33 -0500, Arkansan Raider
wrote:

He said shorts IN it, not ON it. Obviously a few measures of whisky
have found their way into the equipment.
Fine, I won't share any with you.

Party pooper.

Eat my shorts.

LOL

Nice.

---Jeff

[Peter A. Stoll[_2_]]

(Scott Dorsey) wrote:

Sounds like wind noise to me. Where is the closest HVAC vent? Are there
any candles in the hall? Are you near a hot lighting fixture that will be
moving air around?

I suggest trying the Olsen Audio Group WindTech screens, which are only about
$20 and pretty acoustically transparent. They are not as effective as the
Rycote Baby Ball Gag but they are much cheaper and still very good.


Here is an update on this problem for which I solicited advice in this group and also at
the forum Sound Devices operates for 722 owners. A couple of people responding
there were in the air movement camp as well (Jon Tatooles was one).

While the US-2 WindTech screens cost me $35 each, that was still dramatically
cheaper than BBG, and I judged they would be less obtrusive in the live concert
performance venue.

This last week the same group performed in the same venue, and I used rehearsal time
to test the effect of the wind screens on October 7, 2010, and used the screens in
recording the concert October 10. I think there is strong evidence that air movement
impinging on the microphones was the problem, and that the WindTech US-2 is an
extremely effective solution for the specific air movement present last week, and
plausibly would have worked adequately in May. The HVAC configuration in operation
differed between the two dates--hence my minor hedging.

I've added the evidence that this solution works at the end of the original posting at:

http://home.comcast.net/~archae86/thud1.html

My thanks to all who made suggestions, questions, or comments, but particularly to
Scott, who pushed me firmly on the path to a solution that seems to work for me.

My name may appear twice--new newsreader that I don't yet know my way around.

Peter A. Stoll
former microprocessor person