Hi Alex, all
...but PDs dB goes to 0, because we have to have the numbers following the same scheme - so that 0 means 0 always I think. Industry uses dBFS (deciBel Full Scale) because it is measuring the signal against the full scale from -96dB in 16bit recordings to 0dB (all bits used).
Basically, the reason for dB is that our ears hear sound in a non-linear fashion, rather like frequency in fact which is why we have [mtof]
Each drop of (n)dB will be heard as the same amount of reduction in loudness, whereas every linear drop is different perceptually. So, if you have a signal at 96dBPD (-4dBFS) and you set it to 90dBPD (-10dbFS), the loudness will be heard to drop by the same amount as when you then set it to 84dBPD (-16dBFS). In fact, you have halved the amplitude twice, so it is a quarter of what it was, but each drop is heard as the same. This is the difference between amplitude (linear [*~ ]) and loudness (logarithmic)
...so you could relate dB to pitch accounting for the energy at different pitches quite simply, if you use inputs to [dBtorms] and [mtof] in some form of inverse-proportion.
[dbtorms] | [*~ ]
Best, Ed
Alexandre Quessy listes@sourcelibre.com wrote: Hi all,
2007/2/8, Frank Barknecht :
Yes, it's new. You could use the [list-len] abstraction from [list]-abs instead, but you need to check out an older version, because the newest one just wraps [list length].
zexy's [length] also does the job, as far as I know.
As I can see, I am still very bad at using the dB unit for audio amplitude... Anyone has a rule of thumb for this ? Should I use dB with a simple ADSR filter, let say ? I know that if you use them, -6 dB is somewhat half as loud and +6 dB is twice as loud. Great. Now, in pd, 100 is unity while in the industry, the consoles use 0 for unity level. 0 in pd is minus infinity, as far as I know. Now, what is usable ? After a drop of a few dB, we don't hear anything. Perceptualy, I find the standard [*~] range of numbers more linear than using the dB scale.
So, the RMS kind of mean the actual amplitude of the vibrating membrane of the speaker... http://en.wikipedia.org/wiki/Audio_power : hence we use [- 100] [dbtorms] for the conversion. Anything else one should know ?
Perhaps I should put it somewhere on puredata.org after. :)
Alexandre Quessy http://alexandre.quessy.net
PD-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
/
/
| |
<======>
| |
/ \
Lone Shark "Aviation" out now on http://www.pyramidtransmissions.com http://www.pyramidtransmissions.com/process.php?pname=ShopfrontProcess-Start
The all-new Yahoo! Mail goes wherever you go - free your email address from your Internet provider.