[alsa-devel] wrong decibel data?
Werner Van Belle
werner at yellowcouch.org
Sat Apr 10 08:56:55 CEST 2010
Raymond Yau wrote:
>> Yes about that. I always wondered how they come up with 96dB ?
>> A perceived doubling of volume is normally assumed to be +3dB,
>> (log_10(2)=0.3) which means that if you have 16 bit audio you have 16
>> 'doublings', or in essence only 48 dB. Even worse, since the last bit is
>> a sign bit, you essentially can only achieve a dynamic range of 45dB !
>> Now, I know this is off topic, but I never heard any good explanation
>> why CD audio is suddenly 45 dB ? If anybody knows, please share your
>> thoughts !
> When referring to measurements of amplitude it is usual to consider the
> ratio of the squares of *A*1 (measured amplitude) and *A*0 (reference
> amplitude). This is because in most applications power is proportional to
> the square of amplitude,
> in electrical circuit , dissipated power is typically proportional to the
> square of voltage or current
Okay, that would then only make for a factor two. Instead of 45dB one
gets 90dB, this is still not 96dB as ordinarily claimed ?
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