[78-L] waveforms

[DAVID BURNHAM]

Here's a question for the techies. I'm looking at a wave form of a 
recording of human voice. (not whale singing).

The amplitude of the positive part of the waveform is higher than the 
negative side.

What causes this? How does this affect the sound? And is there a fix, 
assuming it is needed?
-- 
Joe Salerno


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is perfectly normal and requires no fix.  While the positive and the negative halves contain the same amount of energy, the positive half contains more high frequency content than the negative half.  This is true of any audio signal;  if you take a single cycle of the waveform and somehow measure the enclosed area of the positive half and the negative half, (don't ask me how to do this), you'll find the enclose areas are identical.  But the high frequency components of the positive half will have a higher amplitude, hence they'll appear to be higher than the depth of the negative half.  This is why it's important that your speakers are connected in such a way that the positive half of the waveform produces a compression of air, a positive transient will travel in air much more efficiently than a negative transient, (try sucking out birthday candles rather than blowing them out).  You may ask how we know that there's the same amount of energy
 in the positive halves and the negative halves if we have no way of measuring it, (maybe there is a way but I don't know about it), the answer is simply that every sound producing device, be it a musical instrument or a speaker, comes back to its rest position when the sound ends, hence all of its positive travels and negative travels are equal.  

db