mobile phone interference on recordings
David@liminal
from what sounds like a mobile phone. I've never had this problem
before and was wondering where the most likely cause of the problem
was (after the phone itself obviously). Are certain types of
microphone more likely to be susceptible to this kind of interference,
might the problem indicate a problem with the mic or is it more likely
to be my cables? I'm guessing the audio interface/ computer is less
likely to be a problem.
Thanks
David
William Sommerwerck
You should check all the obvious things, especially the condition of the
cables.
I was taught a trick more than 25 years ago when I ran into RFI from a TV
station -- coil the mic cord around the mic stand as many times as
practical. This added enough inductance to "choke" the RF (a VHF TV signal,
in this case).
Peter Larsen
> I made a live recording last week that was blighted by interference
> from what sounds like a mobile phone. I've never had this problem
> before and was wondering where the most likely cause of the problem
> was (after the phone itself obviously).
:) .. poor pcb design somewhere is my first guess.
> Are certain types of
> microphone more likely to be susceptible to this kind of interference,
There is a reason for using balanced wiring with microphones and for using
double screened mic cable.
> might the problem indicate a problem with the mic or is it more likely
> to be my cables?
Affirmative.
> I'm guessing the audio interface/ computer is less
> likely to be a problem.
You say zero, zilch, nada about the actual setup and wants us to
troubleshoot it for you?
> Thanks
Take items 1) a mobile phone and 2) your equipment and determine what items
that don't like it at what distance. When you know what object doesn't like
it, then come back and ask, and then perhaps someone can provide suggestions
without typing 3 megabyte if-then.
Kind regards
Peter Larsen
> David
Mike Rivers
> I made a live recording last week that was blighted by interference
> from what sounds like a mobile phone.
> Are certain types of
> microphone more likely to be susceptible to this kind of interference,
> might the problem indicate a problem with the mic or is it more likely
> to be my cables?
It's almost certainly being picked up by the microphone or mic cable.
Countryman
recognized this problem early on and came out with a model of their
miniature
microphone that had an RF filter built right into the mic. A couple of
other mics
have since appeared with similar filtering, mostly those designed for
either
attaching to the speaker's clothing or attached to a podium. Those are
where
cell phones are most likely to be close enough to cause a problem.
But, yes, this is getting to be a more common problem. You can test
your own
equipment with a cell phone to see where the pickup is worst. Miniature
mics that
connect to a "belt pack" (either wired or wireless) tend to be most
susceptible
since the wire connecting to the mic element is usually single conductor
(unbalanced)
for flexibility and easy concealment, so not only the mic, but that
length of cable,
acts as an antenna for the RF interference from the phone.
David@liminal
Thanks for your responses. I should have added that my set up was as
follows:
Soundfield SPS200 A-format mic into Prism Orpheus firewire interface
(using the prism's pres). The SPS200 outputs on a single 10 pin plug
which breaks out four XLRs, 10 meters or so.
David
Scott Dorsey
Could be any of the above. Get a GSM phone, set your system up, and start
disconnecting things until you find where the signal is getting in.
Could be something that should be grounded isn't. Could be something is
grounded twice when it shouldn't be. Could be all kinds of things, and
the way to find it is through systematic troubleshooting.
GSM is a freaking nightmare. It's as if the waveform is designed to cause
as much havoc in audio systems as possible.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Mike Rivers
> I should have added that my set up was as follows:
> Soundfield SPS200 A-format mic into Prism Orpheus firewire interface
> (using the prism's pres). The SPS200 outputs on a single 10 pin plug
> which breaks out four XLRs, 10 meters or so.
Where was the mic relative to the suspected phone? I'd think that most
of the time, a Soundfield mic would be placed several feet away from anyone
carrying a mobile phone, or anywhere (a table or shelf) where someone may
have left one. The interference that's typical from these phones occur when
the phone is within a foot or so of the mic, and it's usually not a
problem if the
phone is a couple of feet away.
Are you sure the interference was caused by a phone? There are all sorts
of unexpected sources of EMI in this modern world we live in.
Arny Krueger
news:7832d33a-59b8-4af7...@p35g2000yqh.googlegroups.com
> I made a live recording last week that was blighted by
> interference from what sounds like a mobile phone.
Until you know the source more precisely, this is going to be tough to
diagnose.
Was the speech at all intelligable? If it was, then it came from a legacy
( non digital) source.
> I've never had this problem before and was wondering where the
> most likely cause of the problem was (after the phone
> itself obviously).
Generally, it takes a very powerful transmitter to intefere with a sound
system.
> Are certain types of microphone more
> likely to be susceptible to this kind of interference,
Other than being open to RF leakage, the susceptibility is more likely to be
in the mic preamps.
> might the problem indicate a problem with the mic or is
> it more likely to be my cables? I'm guessing the audio
> interface/ computer is less likely to be a problem.
RF interference with line level signals is rare. Computer interfaces with
built-in mic preamps are likely to be well-shielded and EMI-competent to
avoid interference with the digital parts of the interface itself.
Soundhaspriority
GSM phones, specifically narrowband GSM, can nuke anything, regardless of
shielding. These phones are used by AT&T and T-Mobile, though they are being
supplanted by WCDMA phones, which should not be any worse than CDMA as used
by Verizon and Sprint.
Bob Morein
(310) 237-6511
Richard Crowley
> GSM is a freaking nightmare. It's as if the waveform is designed to cause
> as much havoc in audio systems as possible.
Not completely unlike the jammer stations that the USSR, et.al. used to
use to try to keep their serfs from hearing RFE, VOA, etc. Except that
the jammer stations ran continuously while cellphones only put out the
occasional bzzt, brrrrrup, brrrrrup, brrrrrup. OTOH, it is the intermittent
nature that makes it more difficult to debug.
David@liminal
I was using the mic in this instance just to record a poet giving a
recital. The mic was only 3 feet from the reader and I'm guessing the
phone was hers. I only used the soundfield mic because I wanted to
get a fairly tight hyper-cardioid pattern and all my other mics are
omnis. I'm not _sure_ it was a phone but I can't think what else it
could have been.
DP
David@liminal
The speech is certainly intelligible, it's just that the interference
is annoying and would certainly be unacceptable for any kind of
release (not an issue in this case). I'm really surprised to learn
that the problem could be in the pres rather than mic or the cables.
I'm never going to be able to replicate the exact conditions of the
problem unfortunately as I'm unlikely to either use that room again or
be in any proximity to the particular phone that caused the problem.
Other than waving my own phone around (cell phones are frequently on
in my studio and I've never had a problem before), are there any
recommended ways of generating RF deliberately to test the resistance
of individual components?
DP
Soundhaspriority
"Richard Crowley" <rcro...@xp7rt.net> wrote in message
news:zaidnTGB0rSpwI3W...@posted.pcez...
GSM is high enough in frequency, yet comparatively narrowband, so the signal
can leak around shields.. My worst experience was with a 1/4" Behringer
measurement mike. Even though the diaphragm is protected by a screen, there
is enough leakage between the screen and the capsule casting to cause a
problem. The capsule amplifier is most vulnerable, because of the gain.
The r.a.m.p.s. people have many stories about this. Anything within 10 feet
is in danger, possibly further.
Bob Morein
(310) 237-6511
Mike Rivers
> I was using the mic in this instance just to record a poet giving a
> recital. The mic was only 3 feet from the reader and I'm guessing the
> phone was hers.
It would be worth some experimenting at home to see if you can hear
interference from a phone 3 feet from that mic.
> I'm not _sure_ it was a phone but I can't think what else it
> could have been.
It's anyone's guess. Some 20 years ago I was doing regular programs in
an auditorium in one of the Smithsonian buildings and I got a whistle for
a few seconds every hour. I eventually discovered that it was something
that went through the power lines to synchronize all the clocks in the
building. A better power line filter got rid of it.
Scott Dorsey
>Until you know the source more precisely, this is going to be tough to
>diagnose.
>
>Was the speech at all intelligable? If it was, then it came from a legacy
>( non digital) source.
GSM phones make a very clear popping kind of sound, usually in multiples
of several pops which repeat every few minutes. It is a horrible
nightmare and it probably the #1 audio EMI issue today.
Steve King
news:heonhm$5d3$1...@news.eternal-september.org...
I've had interference from GSM cell phones at distances up to 20 to 30 feet
including in areas separated by office walls from the recording area. One
was with a Lectrosonics wireless into a 302 into a Sony 537, not cheap
stuff. There was no time to assess which equipment or cable was at fault.
In that case it was possible and easier to move the phone (and the person it
was attached to) out of the area.
Steve King
Ty Ford
(in article <hern8h$9l0$1...@news.albasani.net>):
Then there were the dreaded Nextel Phones at Vulcan Hart........
Regards,
Ty Ford
--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar player?:http://www.youtube.com/watch?v=yWaPRHMGhGA
Soundhaspriority
"Scott Dorsey" <klu...@panix.com> wrote in message
news:herh14$56i$1...@panix3.panix.com...
The sound I've heard is a rough buzz/tone on/off a bit like Morse code.
WCDMA should be much more benign.
Bob Morein
(310) 237-6511
Steve King
news:0001HW.C736E5E3...@News.Individual.NET...
That was one of the sessions I was thinking of. Just plugged a couple of
clips from that video series into a new video demo I've put together for a
prospective client. Audio sounds great.
Steve
Scott Dorsey
>
>The speech is certainly intelligible, it's just that the interference
>is annoying and would certainly be unacceptable for any kind of
>release (not an issue in this case). I'm really surprised to learn
>that the problem could be in the pres rather than mic or the cables.
>I'm never going to be able to replicate the exact conditions of the
>problem unfortunately as I'm unlikely to either use that room again or
>be in any proximity to the particular phone that caused the problem.
If speech is intelligible, I would suspect AM radio interference first
off. Was this near a big AM station?
Go back to that room with your system and try to replicate it.
>Other than waving my own phone around (cell phones are frequently on
>in my studio and I've never had a problem before), are there any
>recommended ways of generating RF deliberately to test the resistance
>of individual components?
A GSM cellphone is handy. I use use a 1W VHF walkie-talkie for basic
testing.
Ty Ford
(in article <hes0b8$pd5$1...@news.albasani.net>):
>> Then there were the dreaded Nextel Phones at Vulcan Hart........
>>
>>
>> Regards,
>>
>> Ty Ford
>
> That was one of the sessions I was thinking of. Just plugged a couple of
> clips from that video series into a new video demo I've put together for a
> prospective client. Audio sounds great.
Thank you, Steve. The company (and lunch) was the best.
Regards,
Ty
tonewheel
I've recorded a sample of that sound into my Korg Triton, and
occasionally when the band are setting up I play the sample. Gets them
every time :-)
Arny Krueger
The speech is certainly intelligible,
Then it isn't coming from a cell phone.
Mike Cleaver
Cell Phones are constantly being polled by the service provider.
You'll hear it every few minutes.
The sound this makes is easy to identify.
I'd post a file but you can't do that here.
Best thing, turn the damned thing off when recording.
When I'm recording a client, I make sure she or he leaves his or her
cell turned off.
I've picked up the interference when the phone is left anywhere near
the computer.
I realize recording in a live situation such as a concert it will be
impossible to get everybody to turn off their phones but I notice some
venues have signs posted asking patrons to shut off their phones while
the performance is underway.
And yes, I've heard cell interference at concerts as well.
Richard Crowley
> "Arny Krueger" wrote:
>> "David@liminal" wrote ...
>> The speech is certainly intelligible,
>>
>> Then it isn't coming from a cell phone.
>
> Cell Phones are constantly being polled by the service provider.
> You'll hear it every few minutes.
> The sound this makes is easy to identify.
But it never sounds like speech in any way. If the OP can hear speech,
then we can conclusively determine that the interference is definitely
NOT coming from any kind of cell phone.
Arny Krueger
Agreed, and that is a very important point.
Don Pearce
In France they call the sound Galloping Horses, although just to be
awkward they do it in French. Pretty good description, I would say.
d
Richard Crowley
> (Scott Dorsey) wrote:
>> GSM phones make a very clear popping kind of sound, usually in multiples
>> of several pops which repeat every few minutes. It is a horrible
>
> occasionally when the band are setting up I play the sample. Gets them
> every time :-)
That's pretty evil! I love it! :-))
OTOH, I attended a live stage-play several months ago and they
had made up a sound-collage of ring-tones from a dozen different
kinds of cell phones. It was the intro and background "music" for
the announcement for everyone to turn off their cell phones.
I thought it was a particularly effective use of humor to get the
message across.
Richard Crowley
> I've had interference from GSM cell phones at distances up to 20 to 30
> feet
> including in areas separated by office walls from the recording area. One
> was with a Lectrosonics wireless into a 302 into a Sony 537, not cheap
> stuff. There was no time to assess which equipment or cable was at fault.
> In that case it was possible and easier to move the phone (and the person
> it
> was attached to) out of the area.
My favorite is the director who (reputedly) has the policy of confiscating
offending phones/PDAs, etc. from cast and crew alike. He reportedly
brings his own hammer and nails them to the doorpost (or fencepost).
Laurence Payne
>
>OTOH, I attended a live stage-play several months ago and they
>had made up a sound-collage of ring-tones from a dozen different
>kinds of cell phones. It was the intro and background "music" for
>the announcement for everyone to turn off their cell phones.
>I thought it was a particularly effective use of humor to get the
>message across.
>
I've seen a few shows where the "turn your phone off" announcement was
the most entertaining part of the evening.
Mark
I attended a talk by Dr Ruth....Before she came out on stage the MC
made the standard announcemnt, .... before Dr Ruth comes out,
everyone please set your cellphones to UM VIBRATE..... everyone
burst into laughter...
Mark