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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