[BC] Re: Super Modulation and distortion

[Mark Humphrey]

At one of the Syracuse SBE conventions back in the '70s, I asked Leonard Kahn this question too -- just after he introduced the "Non-Symmetra-Mod" (later renamed the "Good-n-Loud") which was the box that forced a symmetrical waveform to become asymmetrical.  Or -- in the case of voice that had already passed through a Symmetra-Peak -- to become asymmetrical *again* !   He explained that you can get away with this process (to a certain extent) because harmonic distortion generated by artificial asymmetry tends to be even-order and "pleasing to the ear".
 
So I asked why even-order harmonics are considered "good" and odd-order "bad", and he recomended a book called  "Hearing, Its Psychology and Physiology" by S. Smith Stevens and Hallowell Davis.  But I had trouble finding a copy -- it was written in 1938 and long out of print (although I just learned it was reprinted in 1983 and now available from the ASA)
 
Several years later, I found it in a dusty back corner of a library at Syracuse University and made a photocopy of the entire text.  Good reading, if you want to learn more on the subject of "psychoacoustics."    Their method of measuring the distortion generated within the ear is especially interesting.  
 
Synopsis:   http://asa.aip.org/books/hearing.html
 
Order Info:  http://asa.aip.org/publications.html#pub14
 
Anyone here still using a "Good-n-Loud" on the air -- or if you tried one in the past, would you care to comment?    I have one in my personal collection of unusual processing boxes. 
 
Mark


Barry Mishkind <barry at oldradio.com> wrote:

But, isn't asymmetrical modulation really distortion by definition .

It has been too many years, but I seem to recall that past
around 150-170%, you are so asymmetrical that the
distortion becomes annoying to the listener.

....voice not included.




		
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