## #math - Sun 1 Apr 2007 between 00:40 and 00:55

### NY Lost Funds

 TRWBW JabberWalkie: but its seperable, so you can write it as applying 1D convulution twice, once in x, once in y JabberWalkie TRWBW: can i still have the relation F[ f*g]= F[f] F[g], with a 2 dimentional fourier transform? TRWBW JabberWalkie: yes holst "Life is good" :P JabberWalkie sweet.. holst its a bit ironicwe think of theorems as gifts of the gods JabberWalkie we do? holst but actually they are just a product of the axioms we setup to begin with ^Manu hey peoplei'm trying to understand this magic 'decibel' curve..i am writing some software which sets the audio level in decibels... but i want the volume to behave as a linear quantity..but i cant work out the decibel graph, which i need to understand so i can negate it into a linear graph.ie, 0.5 volume should be half as loud, not damn near silent as it is given half the decibel range. holst the graph is monotonic right? ^Manu in what sense? holst that means for any y=f(x) on the curve you can find g(y)=x. solve for x ^Manu this is amplitude, not frequency.i have no idea.i just know i set the level in decibels.. but i dont really understand what a decibel is..its used in so many different fields.. holst but what are you saying ^Manu its obviously graphable, its some sort of curve.well see the amplitude is set by some function of the level value in decibels...but i dont know that function :/i just want to set the amplitude to my value directly.. but directsound doesnt provide any interface for that..so i need to calculate the correct level, in decibels to get what i want.. which i dont know how to do. holst you insert something in [0,1] range to the directsound api?1 = maximum vol; 0 = silent JabberWalkie ^Manu: somthing at 60db is 10 times louder that 50db..... ^Manu no, i insert something in [DSBVOLUME_MIN, DSBVOLUME_MAX] range to dsound./ JabberWalkie 70db would be 100 times louder than 50dbetc.. ^Manu so if i have v in [0, 1]... and i use (DSBVOLUME_MAX - DSBVOLUME_MIN) * v..i get a totally non-linear volume control ;)which is obvious, but i dont know how to solve it. holst decibel is related to what the human ear think is "loudness" http://www.phys.unsw.edu.au/jw/dB.html#log ^Manu i realise that.. i understand its concept.. but i dont understand it mathematically... holst ^Manu: most probably the volumne in the api isnt dB ^Manu so i cant effectively cancel it out.. because really i just want to address the amplitude coming out my speakers directly without dsound messing with it..