[ARC5] dB Power and QRP according to HR magazine. [Was dB - Apples & Oranges]

Wed Oct 30 15:08:17 EDT 2013

hello all
I had a human sensory perception course in college and in that course i was introduced to the concept of a JPD-- Just perceptible difference, ie the smallest increase or decrease of a sensory stimulus that was detectable as a change.  of course the JPD is depends upon a lot of factors which  for audible JPD as was pointed out earlier in this string includes tone frequency spectral purity, amplitude observer motivations and many others

My personal very rough rule of thumbs are
1 dB is about 1 JPD for experienced motivated observers  ie CW ops
3 dB is about 2 JPDs for experienced ops or 1 JPD for motivated but inexperienced observers-- ie ordinary people not hams/cw ops

8-10 dB produces the impression of a doubling or having of an audible stimulation'

Seeing as the amplitude response of human hearing is logarithmic such numbers and ratios are sorta- kinda- correct.

bruce

On Wednesday, October 30, 2013 2:36 PM, Leslie Smith <vk2bcu at operamail.com> wrote:

>"I believe it started as saying 1dB is too small of a change for the human ear to detect and morphed to become 
> 1 dB is the minimum change that the ear can detect.  This sort of morphing is common."  - Bill

Hi Bill
I see you understand the process that barristers (an Australian
high-level lawyer) use in court during cross examination.

Years ago an article appeared in "Ham Radio" magazine relating the
ability of a human ear to detect a change in sound level.

The article was quite interesting - even though the measurements were
done on an informal basis using only uncalibrated equipment that might
be found in a well equipped "ham" shack.. After a half-hearted search I
couldn't find the article, but it was definitely published by "HR".    

If my memory is correct the author of that article found the change in
power (i.e. dB) was greater than the figure most have quoted in this
thread, and well above 1 dB.  The article drew the conclusion that under
good conditions a 5 or 10 watt QRP transmitter may make effective DX
contacts - and that a 100W or 400W signal might be heard 'better' but
that QRP was still worth-while. 

Some will criticize the method, some will criticize the equipment but I
applaud the idea of doing the work and observing the result.
My observation is this:  "Knowledge gained by personal effort is often
of a better quality than knowledge gained by other means."

  73 de Les Smith
  vk2bcu at operamail.com

On Thu, Oct 31, 2013, at 2:47, Fuqua, Bill L wrote:
>    I believe it started as saying 1dB is too small of a change for the
>    human ear to detect and morphed to become 
> 1 dB is the minimum change that the ear can detect.  This sort of
> morphing is common. An example, my wife 
> was told that adding green beans to our dogs diet prevents gas. However,
> I am sure that it began as green bean
> don't cause gas as some other do. Anyway, she puts green beans into his
> dinner bowl, which is OK since he
> enjoys eating some "people food".
> 
> 73
> Bill wa4lav
> 
> 
> From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on
> behalf of Brian Clarke [brianclarke01 at optusnet.com.au]
> Sent: Wednesday, October 30, 2013 1:47 AM
> To: hwhall at compuserve.com; ARC-5 list
> 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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