Re: Extracting Amplitude Data from Linear PCM on the iPhone
Re: Extracting Amplitude Data from Linear PCM on the iPhone
- Subject: Re: Extracting Amplitude Data from Linear PCM on the iPhone
- From: tahome izwah <email@hidden>
- Date: Fri, 1 Oct 2010 08:04:52 +0200
2010/9/30 Roman Thilenius <email@hidden>:
>
>>> What do the max min values mean in the physical wave form/air pressure?
>>
>> They describe the maximum positive and negative air pressure that can
>> be measured using that representation and its corresponding digital
>> values.
>>
> there is no direct relationship between LOUDNESS and a digitial or analog
> signal, it is always relative, and depends on frequency ... and
> amplification.
I wasn't referring to loudness, I was referring to air pressure.
Loudness involves the human perception and we weren't discussing this
at this point.
> i would exlude the 0. from the log() and translate the value 0 directly to
> -90.0 db/A
0 is -∞ dB DFS no matter what scale you're using. If you're resolving
down to -96 dB (not -90 btw - check your math!) the softest signal
that you can represent with the LSB will be at that threshold.
Zero still means absolute silence which is at -∞ dB (hence the range
error when feeding 0 into log10()).
--th
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