Radio microphone noise

[Derek Roff]

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.  The problem is that I am shooting five hours in a 
row, each day.  I don't have that much battery capacity between charge 
cycles, if I use the lcd view screen.  If I use the viewfinder, the 
batteries may last, but my brain will be destroyed by five hours of 
squinting through the vewfinder.

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.

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.

Thanks for you thoughts,

Derek

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu