At 12:14 PM 9/30/2014, DAVID BURNHAM wrote:
> I have not experienced nor can I imagine why a trombone would have
> negative spikes. The only explanation I can think of is that the
> absolute polarity of the microphone has been reversed, but that would
> affect trumpets as well.
The query that started this thread was about a live recording made in the
1970's. When I first started doing live sound work in 1970, I built a
device which measured polarity of microphones, because I understood that it
was important that the mics all have the same polarity. When I first
measured the several dozen mics in our collection, the results were 60% pin
2 + and 40% pin 3 +. There was no standard for which polarity was correct
-- it varied from one manufacturer to another, and even in some cases over
time with a single manufacturer. And, I doubt that polarity was checked in
manufacturing test, because one day a recording company showed up with a
brand new matched pair of Neumann mics, and we found that they had opposite
polarity. Oops! Thus, I would not be at all surprised to find that
different instruments in a 1970's recording have different polarities.
> As far as why a woman's voice would have higher spikes than a man's
> voice, my explanation, (which everybody is welcome to argue with), is
> that every human voice, male and female, has the same amount of high
> frequency energy - mainly consonants. But a male voice has much more low
> frequency energy which might tend to mask some of the high frequencies,
> especially if he's close to a mike which might lop off the spikes.
I've done enough dialog editing to know that a few male voices are quite
asymmetrical. Broadcasters discovered asymmetrical voice waveforms long
ago. For those interested in audio history, Google "Kahn Symettra-Peak" to
read about a device patented in 1959 which claimed to fix this problem.
-- John Chester