Fletcher Munsen curves !?

john john wrote:
>>music. Converting signal level to decibels is simple. Iv the signal is
>>in  RMS (or other average measure) volts, decibels is 20*log10(signal).
>>To convert to absolute level, add a (usually unknown) constant.
>>
> 
> 
> 
> If I've an array of values and I send it to a sound card this will
> reproduce all these bits in speaker movements. Right? How I can know
> what is the value in volts from these bits? Ok you say "or other
> average measure" but I would like to know which are these "other".
> Excuse for my ignorance but I'm totaly new at this kind of analysis.

There is no way to know with calibration. The sensitivity of the 
microphone, the gain of any intervening amplifiers, what full scale on 
the ADC and DAC mean, the output amplifier gain, and the loudspeaker 
efficiency together determine how the sound pressure of the program 
material translates to reproduced sound pressure. The set of 
Fletcher-Munson curves, when properly applied, allows one to maintain 
approximately the same frequency balance despite differences in those 
sound pressures. Fletcher-Munson correction is usually applied "by ear", 
and it is usually overdone.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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Jerry Avins wrote:

   ...

> There is no way to know with calibration. 

[wolf howl] There is no way to know *without* calibration.

   ...

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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