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Topic: Logarithmic volume control (Read 6115 times) previous topic - next topic
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Logarithmic volume control

Hi. Could anyone please help?

I use the logarithmic volume control toolbar 1.4 that ranges from -60dB to 0.0dB (btw why not from -100dB as I can do with hotkeys?).
1. If I set the volume to -6dB, the slider is right in the middle of the toolbar. If I understand it correctly, the slider position shows the actual percieved loudness (or whatever should I call it?)So,-6dB is actually half as loud as 0.0dB, not -30dB? Why then the built-in (+/-) volume control in f2k works on a fixed 0.5dB scale? Btw, I read we can only hear a differnce of 1dB, not less. Also, the hotkeys I can assign for volume change do not allow me to change volume logarithmically (just 0-3-6-9-12-15-18-21). Why?
2. I would like to bind digit buttons (0-9) on my remote to pass to f2k via girder 10 volume levels in dB that would represent steps of actual percieved loudness (I mean pressing button "5" should set f2k to 50% of actual percieved loudness, button "7" to 70% etc.). Some kinda discrete logarithmic volume knob on a stereo. How do i calculate all this? I am not too good at logarithms...

As of now, I just put a regular rooler against the volume toolbar and came up with something like this:

20% - 14.60 dB
30% - 10.72 dB
40% - 8.04 dB
50% - 6.00 dB
60% - 4.35 dB
70% - 2.96 dB
80% - 1.76 dB
90% - 0.70 dB
100% - 0.00 dB

I understand it's silly. What is the formula?


Thanks in advance and excuse so many why's.

Logarithmic volume control

Reply #1 –
Quote
... So,-6dB is actually half as loud as 0.0dB, not -30dB?
[a href="index.php?act=findpost&pid=289931"][{POST_SNAPBACK}][/a]

I think it should be -3dB (correct me if I'm wrong!) for half of the sound "energy" at 0dB. This probably direct related to half loudness at -3dB compared to original loudness.


Quote
2. I would like to bind digit buttons (0-9) on my remote to pass to f2k via girder 10 volume levels in dB that would represent steps of actual percieved loudness (I mean pressing button "5" should set f2k to 50% of actual percieved loudness, button "7" to 70% etc.). Some kinda discrete logarithmic volume knob on a stereo. How do i calculate all this? I am not too good at logarithms...

As of now, I just put a regular rooler against the volume toolbar and came up with something like this:

20% - 14.60 dB
30% - 10.72 dB
40% - 8.04 dB
50% - 6.00 dB
60% - 4.35 dB
70% - 2.96 dB
80% - 1.76 dB
90% - 0.70 dB
100% - 0.00 dB

I understand it's silly. What is the formula?

Thanks in advance and excuse so many why's.
[a href="index.php?act=findpost&pid=289931"][{POST_SNAPBACK}][/a]


I second your suggestion, it's easier to manage the volume like the window's master volume control.

dB is a more technical value compare to the %. The volume tunning in dB might not suitable for some ppl who has no accoustic background and confuse the use a lot. May be the author can implement an additional option to switch between the dB and volume in percentage for volume tunning? 

=========================================
According to what I know, the logarithms calculation of dB is....
xxx dB = 10 log(EnergyOut/EnergyIn)        => The sound energy
Or
xxx dB = 20 log (VoltageOut/VoltageInput) => for sound measured in voltage

For sound energy, it's proportional to measured sound voltage^2 (i.e. VoltageOut & VoltageInput). You will find that if the output sound energy is half of the input energy (with is the sound loudness) => 10*log(0.5) = -3dB!


Someone pls correct me if I'm wrong, I probably returned what I had learn from my teachers. 

Logarithmic volume control

Reply #2 –
From what you're saying, it looks to me like the "log" volume control actually has a linear visual scale.

I always reckoned that half amplitude = half as loud = -6dB, but many text books suggest -10dB for half as loud - my ears disagree!

Most volume controls (real world ones) are basically logarithmic, but usually deviate from this at the lower end of the scale (for very sensible reasons, if you think about it!)

Cheers,
David.

Logarithmic volume control

Reply #3 –
http://www.hydrogenaudio.org/forums/index....showtopic=21504

Quote
Quote
3db essentially doubles or halves the "volume".

http://en.wikipedia.org/wiki/Decibel

+3 dB means approximately twice the power, and +6 dB means approximately twice the voltage. +10 dB is, by definition, exactly twice the volume.
[a href="index.php?act=findpost&pid=210109"][{POST_SNAPBACK}][/a]

Note I'm not talking about perceived volume here.

Logarithmic volume control

Reply #4 –
Quote
Note I'm not talking about perceived volume here.
[a href="index.php?act=findpost&pid=290219"][{POST_SNAPBACK}][/a]


Yeah, I saw that before - but if you're not talking about perceived volume, what definition are you using for volume?

Logarithmic volume control

Reply #6 –
is there any way to change logarytmic scale to normal scale for example the same that is in winamp??

Logarithmic volume control

Reply #7 –
well The dB scale is logarythmic, but the right  formula is

20log(I/I0)

-3db corresponds to dividing the volume by sqrt(2) (to confirm, type -20log(sqrt(2)), it's about 3 )

to divide by two, the gain is -6dB

as a consequence to know the gain in dB, the formula is:

20 log (percentage wanted/100) it will give you the gain in dB (always negative as the percentage wanted is always lesser than 100%, but after, it's mathematics and study of the logarytmic function..)

Hope that helps

about the difference between -60dB and -100dB, it only means that instead of multiplicating by 0.1 the original signal (which is already very low; not to say unhearable) you multiplicate by 0.001 the original signal (well, it's already unhearable I think)