Audio Processing (Was: Tropo <is it...>)

["Kaimbridge M. GoldChild" <kaimbridge@my-deja.com>]

Richard Chonak wrote,

> Writers on this list talk occasionally about the "compression",
> "clipping", and other processing applied by radio stations to their
> audio, but all that talk goes over my head, and probably that of other
> readers not versed in audio technology.
>
> Would somebody consider giving a little explanation of what these
> techniques are and what effects they have?   It would be especially
> nice to find out how an attentive listener would be able to recognize
> them.

I'm not an engineer--and I don't play one on TV P=)--but rich audio
processing *is* a fetish of mine.
Basically, it is the added "meat" of audio.
The most pronounced--and easily identifiable--effect is added "decay",
either "reverb"eration or true echo.  Reverb is the auditorium effect
used in a lot of recordings (e.g., Whitney Houston, Elton
John--particularly from the 70s--and a lot of country material):  The
old WVBF-105.7 and *old* WROR-98.5 used to use reverb, rather
generously.  Echo, OTOH, is the alley type "ECHO-ECHo-ECho" used by a
lot of ethnic programmers and foreign broadcasters (e.g., particularly
notorious are the Cuban and Latin American stations <"Raadio
RUMMMMBOOOOooo">):  It's considered more of a special effect, not really
used by mainstream stations.
The other major type of processing employed by stations is
"compression".  Quite simply, compression is the difference between
listening to a record on your home player and how most commercial
broadcasters transmit it (i.e., the added weight, texture and fullness).
While most pop/rock and country stations use it extensively, most EZ
listening, "soft rock", classical and most educational/non-com stations
rarely employ it to any noticeable degree (try tuning from 88-92 <with
the exception of WUMB-91.9, which seems to use a healthy dose--phone
lines?-see below>, then 92-108--you should quickly be able to tell the
difference).
There is a rather extreme form of heavy compression, that I refer to as
"hypnogogic" (like when you come out of a noisy room, usually tired, and
the voices/noises play back in your mind, in a rather vivid, surreal
way), which I think some have defined more technically as "inverted
dynamics"--you can get a rough idea of the effect by "phlanging"
(shifting the speaker balance back and forth, real fast) or bouncing the
volume up and down real fast (the first half of the guitar riffs in The
Rasberries' "Please, Go All The Way" <sic?> is a good example):  Most AM
top-40 stations used it liberally, back in the 70s (WRKO-0.680 *still*
seems to use it, per listening to the station's bumper music,
particularly during network feeds, such as Rush Limbaugh and Art Bell),
but FM avoids it (for one thing, unless it's done right, you can get
rather pronounced left-right "channel shifting" during straight
verbalizing, as well as enhanced sibilance, lessened stereo effect and
an overall withdrawal/distancing of the sound).  The one exception is
sometimes a station runs their feed "through a phone line" (such as when
they are doing something to the studios or transmitter) and this will
unavoidably produce "hypnogogic compression":  The old WKCG-101.3
Augusta ME used to use it full time back in the early and mid 80's, as
did the *old* WJBQ-97.9 Portland (back when Harry Nelson was on-air and
PD)--Dan may know more about those particular stations.
The only stations currently coming close to using "hypnogogic
compression" is WQSX-93.7 and, to a lesser extent, WODS-103.3.
As for the technical details, all I know is that compression involves
several different elements (some of which may be one and the same): 
Gain (input/output volume), gate (?), attack, hold, decay, phlange,
threshold, ratio (?) and release.

     ~Kaimbridge~