Lawrence DčOliveiro wrote:
> In article <42308d00$1_1@127.0.0.1>,
> Robert Cooze <> wrote:
>
>
>>Lawrence DčOliveiro wrote:
>>
>>>In article <422f3a1c$1_2@127.0.0.1>,
>>> Robert Cooze <> wrote:
>>>
>>>
>>>
>>>>Lawrence DčOliveiro wrote:
>>>>
>>>>
>>>>>In article <20050228193203594+>,
>>>>>Roger Johnstone <> wrote:
>>>>>
>>>>>
>>>>>>Traditionally b for bit and B for byte, but alas a lot of people are
>>>>>>ignorant of this tradition. And it is only tradition as these units and
>>>>>>abbreviations have never been officially adopted by any standards body
>>>>>>as far as know.
>>>>>
>>>>>Particularly since "B" already has a an official meaning in SI, as the
>>>>>abbreviation for the "bel", the unit of ratio. 1 B = 1 bel = a ratio of
>>>>>10/1, 2 bels = 100/1 etc (it's logarithmic). A decibel (dB) is one-tenth
>>>>>of a bel, which is a ratio of about 1.26. Coincidentally, a change in
>>>>>sound output power of that ratio is about the smallest that the human
>>>>>ear can detect.
>>>>
>>>>Depending on the actual thing being measured what I lurned at tec and
>>>>proved in experements
>>>>
>>>>A power difference of 3dB is a [doubling] of power
>>>
>>>That's consistent with what I said.
>>>
>>>
>>>>ie if your source was produsing 500mW of power (0.5W) and was dobled to
>>>>1W A human dould decet the difference of the physical output this could
>>>>be light, heat or sound. The point is 3dB is the smallest change up or
>>>>down that we can notice.
>>>
>>>No, for sound it is 1dB.
>>>
>>>For light it seems to be 4dB. This is the ratio between successive
>>>integer steps on the astronomical stellar magnitude scale.
>>>
>>>By the way, Wikipedia says the "bel" is not an official SI unit. So "B"
>>>could still be used for "byte"...
>>
>>I was working form a pure electrical eletronics point of view 3dB of
>>signal gain = doubling of power...
>
>
> Actually that's closer to 3.01dB for a doubling. Log10(2) = 0.3010 to 4
> figures.
>
>
>>...sound or light tranmition from a single point like a light bulb or
>>single speaker is somthing like a to a power of 3 loss the further away
>>you travel away from it...
>
>
> Power of 2 -- inverse-square law for a point emitter. Inverse-cube would
> apply to a dipole emitter.
>
>
>>...where a flat pannel or tube of light is much
>>less lossy ( talking about elexctrostatic speakers and flurenent tubes )
>
>
> That would be inverse-law (power of 1) for a linear emitter of infinite
> length.
>
>
>>what I was trying to say that the dB in its self is normaly nonsencical
>>without [qualification]
>
>
> It's a ratio. That's all I've used it for above.
Thats True
I think from my crustry memory if we were using db to measure sound 1dB
is about the quietest a normal average Human cah hear 100dB is getting
very loud and 120dB is where the pain starts. So In my orignal arguments
with the 3dB using electrical ratio's I should be right but in your
orignal posting about sound you are correct. Proberly time to put the
thrad out of it missery.
--
http://cooze.co.nz home of the RecyclerMan aka Robert Cooze
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