[TowerTalk] 1dB more RF Power?

[jimlux]

On 4/30/20 6:18 PM, David Gilbert wrote:
> 
> I confess to having generated those files, although it was several years 
> ago that I put them on my web site.  They just get referenced here or 
> there about once a year when a similar topic surfaces.
> 
> http://www.ab7e.com/weak_signal/mdd.html
> 
> One dB was about all I could claim was distiguishable, but a difference 
> two dB was surprisingly so.
> 
> 73,
> Dave  AB7E
> 

this is known as the "just noticeable difference" thing and ties into 
the Weber-Fechner law which is really more that perceived differences 
are log scaled (that is, a 3 dB change from 3 to 6 dB is perceived as 
the same jump as 10-13 dB)

for speech it's around 2-3 dB in SNR
(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4335553/  was the first 
hit in general, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4871229/ is 
another - apparently the hearing aid business really cares about this)

However, for detecting tones in noise, or constrained speech, the JND is 
smaller. And, JND isn't necessarily related to intelligibility or 
detectability.

I used to work with tactical comm radios just as digital coding was 
coming into play and there were tons of arguments about various schemes 
of various computational complexity: is CVSD better or worse than mu-law 
with companding at data rate X? What about LPC-10?

It is *highly* situation dependent. What's ok in a tactical situation 
where you just want to call in artillery fire to the correct grid square 
is different than whispering sweet nothings to your sweetie.

This kind of analysis, of course, is why modern cellphone audio quality 
is so bad. Back in the 80s, if someone had said that random consumers 
would be happy with 8kbps encoding of speech they would have called them 
crazy. What we used as the "standard of comparison" was so-called "toll 
quality" which is about 56 kbps, sampled at 8kHz.

This is sort of interesting and describes the "signal detection" 
problem, which is related to the "CW detection" problem

https://www.weizmann.ac.il/neurobiology/labs/ulanovsky/sites/neurobiology.labs.ulanovsky/files/uploads/behavneurosci_lecture13_dovsagi_psychophysics_05july2018.pdf

And of course, the real problem in CW detection is not just a random 
tone in noise, it's a "structured tone sequence" in the presence of 
other "structured tone sequences".

 From a psychophysics standpoint it's an interesting problem