[Alsaplayer-devel] Logarithmic volume scale.

[David Fellows]

On Tue, 16 Dec 2008 01:14:30 +0100 
"=?ISO-8859-2?Q?Adam_Kuklasi=F1ski?=" wrote -
> Hi,
> I'm using Alsaplayer since few days. I like it a lot, but I've noticed
> two drawbacks.
> 
> The volume slide apparently attenuates the signal linearly instead of
> logarithmically. I mean, from what I can hear, the way it affects the
> signal is something like:
> 
> Sout(t) =3D Sin(t) * X
> 
> where Sin(t) and Sout(t) are original signal and the attenuated signal
> respectively, X being the position of the volume slide in percents.
> >From what I know about the nature of human hearing this formula should
> look like that:
> 
> Sout(t) =3D Sin(t) * { 10 ^ [ ( 1 - X ) * 75 / 20 ] }
> 
> Thanks to this "75 / 20" factor, the attenuation done by the
> attenuator is between -75dB and 0dB. This means that in the "loudest"
> position it does nothing to the signal (0db) and in it's minimum it
> lowers the sound level by 75 dB (the magnitude is then ca. 5600 times
> lower). The -75dB - 0dB range could and can be changed, but is quite
> optimal. 75dB attenuation causes that very loud sounds, say 90dB, are
> after attenuating only 15dB which is barely audible in normal
> conditions.
> This little change would greatly improve the "feeling" of the volume
> slide. Notice, that there is only small (subjective) difference
> between 100% and 50%, and there is huge difference between 50% and 20%
> in loudness of played music now. With formula above, this subjective
> change of loudness will be spread evenly across the whole range of the
> slide.

I would second Adam's suggestion.

Dave F