[MacDV] Radio microphone noise

[Gregg Gorrie]

on 7/13/04 1:48 PM, Derek Roff at derek at unm.edu wrote:

> I'm shooting video indoors in a classroom, using an Sony trv950 camcorder.
> I've had lots of problems with microphone noise.  Hums and buzzes have
> plagued all my wired microphones.  The wireless mic, Sony WCS 999, has
> given good, clear sound 90% of the time, with aggravating intermittent
> "sssnickk" sounds.
> 
> Today I discovered that the Sony power supply/charger is the source of the
> hum on the wired microphones.  The obvious solution is to unplug the camera
> and run off the battery.

You might be able to eliminate the hum (most likely a ground loop) by making
sure all your equipment is plugged into the same circuit ... try plugging it
all into a surge-protected power bar and then find one AC outlet to plug
into. You may have to experiment to find which outlet gives you the cleanest
audio. 
 
> In any case, the wireless mic is a better choice for capturing the voices
> of the roaming teachers.  The sound that I get, at random intervals from
> three to thirty seconds apart, is kind of a hiss, ramping up in volume
> quickly to a sharp cut off.  It sounds like electronic interference of some
> sort.  The sound reminds me of sound effects in science fiction movies.
> Perhaps the spark traveling up the wires in Frankenstein's lab.  Roughly
> 1/2 second in duration.
> We are in a small building on the campus of a small college in Vermont, a
> mile outside a small town.  I think I am fairly isolated from large scale
> electrical disturbances, radio stations, airport control towers, and the
> like.  No telling how the building is wired.  The lights are incandescent.
> There are dimmers on the light switches, but testing them while listening
> to the microphone through the camera hasn't shown any obvious difference
> between off, on and in between.

Here you might want to experiment with the receiver's placement and
orientation of the antenna. Are there any metal poles/beams around? Do these
glitches happen more often when the talent moves to a certain spot in the
room? Try to get in early and do some troubleshooting.

I've found that these noises happen more often when the batteries are weak.
Make sure you're well stocked with fresh high-quality alkaline batteries.

Also, the quality of the wireless system will be a factor here.
> 
> Any suggestions and speculation will be welcome.  I am also wondering about
> Sound Soap or other software to decrease the severity of the problem in
> post production.\

If the glitches happen between lines of dialog, it's no problem to edit them
out. Unfortunately, if they happen during the speaking parts, the audio
itself temporarily cuts out and you have little chance of repairing the
problem (short of finding other good takes and trying to copy and paste them
- which is a time consuming hit-and-miss proposition at best.

Hope this helps somewhat. Good luck!
 
> Thanks for you thoughts,
> 
> Derek

-- 
Gregg