"Scott Gardner" wrote in message

On Mon, 29 Dec 2003 05:18:44 -0500, "Arny Krueger"
wrote:

"Scott Gardner" wrote in message


Evidently, the FCC has a part in this as well. They limit the peak
levels that radio stations can put out, so radio stations actually
use on-the-fly compressors to raise the RMS level of the music
without exceeding the FCC limits on the peaks. Pretty interesting
stuff.

All the FCC is doing is requiring radio stations to keep their
broadcasts within the frequency band that they are licensed to use,
and within the power limits they are licensed to use. This seems
perfectly reasonable.

The bad guys are the radio stations that are willing to do just about
anything to appear to be louder than anybody else to their listeners.

I thought the FCC had rules regarding the modulation of the signal to
enhance "loudness", as well as the power rating of the transmitter
used.

The FCC has nothing along these lines that can't be finessed. Everything
that is being done can be legal.

So in theory, if a station is broadcasting using the allowed
number kilowatts at their transmitter, they could still run afoul of
the FCC if they improperly used compressors or other devices to play
with the perceived "loudness" of their transmission.

Power isn't the only thing that is limited by a station license. The license
also stipulates a center frequency and a bandwidth. The station has to stay
within it's licensed radiated power, and bandwidth usage limits. If it does
that and meets a few other less important limits, it is legally compliant.

So, it would seem like the FCC regulates frequency use, transmission
power, AND modulation of the signal. Am I wrong here?

The FCC regulates the nature of the modulation of the carrier frequency in
gross terms like AM versus FM.

It would be self-defeating for an AM station to FM modulate their signal in
a big way, because it would waste power. However a little bit of FM happens
due to the imperfect nature of technology. I believe that the FCC has
limits on the amount of incidental FM an AM station can transmit. It's been
a while since I read the rules but I don't think the basics have changed.

Flip this around for FM stations. It would be dysfunctional for them to
transmit much power that was AM, and I think there are limits on how much
incidental AM they can transmit.

However, these issues are all in a different domain than the kinds of
shaping of the transmitted signal that the article at the top of the thread
is talking about.

Look at it this way. I can make a CD that has just about any kind of
amplitude and spectral characteristics. That's the nature of the CD media -
it is extremely flexible. In the audible range, CD media is about as good as
wire in terms of carrying signals. So, radio stations play CDs which means
that the music they transmit can have just about any kind of amplitude and
spectral characteristics. It's not much of a leap from there to the current
situation, where radio stations alter the spectral and amplitude
characteristics of the CDs they play.

The thing about all these alterations is that audiophiles need not be
defeated by them in every case. I've experimented with uncompressing and
reshaping commercial recordings. It can be done, and it can make a positive
difference.

For example. I'm working on a CD of a church choral cantata that was done
with a pre-recorded musical track. These commercial pre-recorded tracks
often sound pretty bad. They are chosen for musical values, not sound
quality. In retrospect, they are often mastered in ways that are contrary to
accepted practice. I don't know what the people who record some of this
stuff are thinking, except perhaps that they want to produce a recording
that will cut through the cheapest SR system under the worst conditions.
That's not our situation.

Before final mixdown I remastered the track. The first two people I've
played a test mixdown for without any cues about how it was made, our
organist and the other SR tech, were very positive about the changes. These
guys can be very critical, but they gave their favorable opinions without
hearing a word from me. I think I'll remaster the track before the
performance, next year.