[ARC5] dB Power Apples and dB Voltage Oranges, was Re: Selectivity Ratings...

[Geoff]

I wouldnt use a recording studio as any reliable indicator, it is purely 
subjective within its own limitations.

Give me a good receiver free of phase and mixer noise, variable selectivity, 
and quality headphones used ahead of the distortion producing audio output 
stage. Then feed that radio with a high end signal generator with no 
discernible signal leakage.

Im 72 and have been copying CW since I was 14 and can dig fairly well into 
the galactic noise on VHF and above as well as the usual atmospherics on 
160/80 for enough signal to make a legitimate contact. Over 325 DXCC on 80 
and almost 300 on 160. VERY good low noise receiving antennas are mandatory.

My TS-940 and TS-950SD are about 23-26 years old and on the air testing some 
of the latest and greatest....according to hype....leaves me cold.

Carl



----- Original Message ----- 
From: "Brian Clarke" <brianclarke01 at optusnet.com.au>
To: <hwhall at compuserve.com>; "ARC-5 list" <arc5 at mailman.qth.net>
Sent: Wednesday, October 30, 2013 1:47 AM
Subject: Re: [ARC5] dB Power Apples and dB Voltage Oranges,was Re: 
Selectivity Ratings...


> You may be referring to the work of Fletcher and Munson in the Bell labs 
> in about 1938. However, their work was based on laboratory experiments 
> with young listeners.
>
> We now know that the ear's ability to pick up slight differences depends 
> on, among other things:
>  a.. age (presbycusis)
>  b.. frequency
>  c.. purity of the frequency (bandwidth, distortion within hearing range)
>  d.. genetic differences
>  e.. one ear or both
>  f.. history of noise exposure (eg, working around tin bashing shops, 
> repairing naval vessels, working on rocket motors)
>  g.. history of hearing damage (eg, tinnitus)
>  h.. disease of cochlear nerve and other parts of the hearing apparatus
>  i.. duration at particular ambient noise levels
>  j.. the 'reward' for hearing something.
>
> 1 dB is a purely mathematical definition and has nothing whatever to do 
> with human hearing acuity, consensual or otherwise. WRT your last 
> sentence, keep wondering.
>
> My own experience from working in sound recording studios is that a 2 dB 
> difference is about the limit that any reasonably experienced person can 
> reliably discern.
>
> 73 de Brian, VK2GCE.
>
> On Wednesday, October 30, 2013 12:25 PM, Wayne said:
>
>
>> Good CW operators
>> can hear as little as 1.5dB change and oft times even under 1 dB will 
>> bring
>> a very marginal signal out of the noise.
>>
>> I seem to recall that the original 1 dB definition was based on a 
>> consensus of the smallest power change in an audio circuit that could be 
>> discerned by the human ear. I've always wondered how they conducted the 
>> tests to arrive at that, though.
>>
>> Wayne
>> WB4OGM
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