Hi,
I have very little knowledge of psychoacoustics, so I was wondering if those of you who did could explain to me if the ALSA (Advanced Linux Sound Architecture) volume mapping makes any sense and why?
In my limited exposure to discussion of loudness/volume/human perception I can't say I've ever come across a mention outside of the ALSA code of a volume (cubic) relationship to linear scale of the voltage of the DAC for human sound perception.
So does this make sense? The interval mentioned is the ALSA 0 to 100 volume scale.
From the alsamixer man page.
It tripped me as odd when looking at the reaction of a Topping D10s (0 to -127 dBfs volume control) to the ALSA volume. Just a few select points as examples.
ALSA Vol / Topping Vol
0 / -127 dB * Huge dB steps at beginning
1 / -105 dB
2 / - 93 dB
48 / -19 dB * At this point ALSA doesn't even use it's full 100 point resolution
50 / -18 dB * because the Topping has 1 dB resolution and 49 would be somewhere in between.
52 / -17 dB
89 / -3 dB
93 / -2 dB
96 / -1 dB
100 / 0 dB * And at the end it takes 4 ALSA steps to even make a 1 dB change.
Certainly it doesn't seem the most efficient use of the available steps.
I have very little knowledge of psychoacoustics, so I was wondering if those of you who did could explain to me if the ALSA (Advanced Linux Sound Architecture) volume mapping makes any sense and why?
In my limited exposure to discussion of loudness/volume/human perception I can't say I've ever come across a mention outside of the ALSA code of a volume (cubic) relationship to linear scale of the voltage of the DAC for human sound perception.
So does this make sense? The interval mentioned is the ALSA 0 to 100 volume scale.
From the alsamixer man page.
VOLUME MAPPING
In alsamixer, the volume is mapped to a value that is more natural for
a human ear. The mapping is designed so that the position in the in‐
terval is proportional to the volume as a human ear would perceive it,
i.e. the position is the cubic root of the linear sample multiplication
factor. For controls with a small range (24 dB or less), the mapping
is linear in the dB values so that each step has the same size vis‐
ually.
It tripped me as odd when looking at the reaction of a Topping D10s (0 to -127 dBfs volume control) to the ALSA volume. Just a few select points as examples.
ALSA Vol / Topping Vol
0 / -127 dB * Huge dB steps at beginning
1 / -105 dB
2 / - 93 dB
48 / -19 dB * At this point ALSA doesn't even use it's full 100 point resolution
50 / -18 dB * because the Topping has 1 dB resolution and 49 would be somewhere in between.
52 / -17 dB
89 / -3 dB
93 / -2 dB
96 / -1 dB
100 / 0 dB * And at the end it takes 4 ALSA steps to even make a 1 dB change.
Certainly it doesn't seem the most efficient use of the available steps.