[BC] Nominations For Best sounding AM

[Robert Orban]

This is a hard question because the answer is "it depends on the 
radio you are listening to and the amount of noise and interference 
on the channel at the location where you are listening." As the 
recent NRSC study showed, AM radios vary widely in frequency 
response, although their mean -3 dB frequency is about 2 kHz. A 
station that sound "harsh" on a wider-band radio may the station that 
best punches intelligibility through on a narrowband radio.

This is why creating processing presets for AM audio processors is 
such hard work. (It's Greg Ogonowski's and my least favorite task in 
developing AM processors.) No matter what you do,  AM audio cannot 
compete with modern, wideband standards (like CDs) because of the 
radios. The presets have to represent a compromise that sounds decent 
on radios that are both narrower and wider than the NRSC mean. For 
the narrowband radios, intelligibility is a real problem because they 
are significantly narrower than the 3 kHz usually considered to be 
necessary to preserve speech intelligibility, at least according to 
the many tests at Bell Labs that created the standard for 
"toll-quality" telephony.

The other problem is the noise and interference environment on the AM 
band. This requires minimizing the peak-to-average ratio of the audio 
without driving listeners away due to artifacts. Audio with a lot of 
dynamics compression is preferred by audiences when the main goal is 
easy comprehension of speech when there is a lot of noise and 
interference. The same amount of processing may sound over the top 
where field strengths are high compared to the noise and interference.

There are, of course, potential audio problems that will take away 
points from any audio quality assessment. Examples are codec 
compression artifacts caused by too many cascaded codecs and/or too 
low a bitrate, and obvious hum and/or noise in the audio. Clipping 
mic channels and program busses are another problem. Clipping should 
be done in one place and one place only -- the audio processor -- so 
that it can be controlled. But assuming that the audio path is clean 
before the transmission audio processor, all you can say is "the 
best-sounding AM is the AM that is best processed for a station's 
target demographic, for the radios that that demographic is likely to 
own, and for the noise and interference environment where they are 
likely to listen."

Bob Orban