What are target volume levels relative to?

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chrisjj
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What are target volume levels relative to?

Post by chrisjj » Fri Sep 04, 2009 8:37 pm

The options' Target Volume Levels are specified in dB, but nothing I can find says what this is relative to. Anyone know? Thanks.
Chris

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Re: What are target volume levels relative to?

Post by nohitter151 » Fri Sep 04, 2009 8:38 pm

By default, 89db. It's specified in the options under 'Volume leveling'.
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chrisjj
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Re: What are target volume levels relative to?

Post by chrisjj » Fri Sep 04, 2009 8:54 pm

nohitter151 wrote:By default, 89db. It's specified in the options under 'Volume leveling'.
Thanks, I know the default value. What I am asking is what are the values relative to. dB is a relative measure ... so e.g. 89dB from what?
Chris

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Re: What are target volume levels relative to?

Post by nohitter151 » Fri Sep 04, 2009 9:11 pm

chrisjj wrote:
nohitter151 wrote:By default, 89db. It's specified in the options under 'Volume leveling'.
Thanks, I know the default value. What I am asking is what are the values relative to. dB is a relative measure ... so e.g. 89dB from what?
I suppose its the same as whatever replaygain uses, so you might want to try googling if you're interested in it.
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Re: What are target volume levels relative to?

Post by rovingcowboy » Sat Sep 05, 2009 1:58 am

the levels are taken from the song file header there is a level set in there for the song and it is marked as 100% so monkey will adjust the level to that 100% so in effect two songs both with 100% marks but one low volume and the other loud volume will be treated the same and still keep their different loudness of each other.

now on jet audio their burner has a feature that will change that file loudness to equal what you set in the option and then burn all the songs to that volume loudness. how ever that is only for the burning. the file on the computer will still be the way it was set to be.

that is completely different then the way mediamonkey 2.5 does the volume leveling. some like me like that jetaudio way of burning the songs. :)
i am not sure if mm 3.1.1.1264 does that or not. :-?
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chrisjj
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Re: What are target volume levels relative to?

Post by chrisjj » Sat Sep 05, 2009 7:35 am

> the levels are taken from the song file header there is a level set in there for the song

Thanks, but the question is not about the levels in the song (track) file. It is about the target volumes in the MM Options.

> now on jet audio their burner has a feature that will change that file loudness to equal what you set in the option and then burn all the songs to that volume loudness.
> am not sure if mm 3.1.1.1264 does that or not. :-?

I think it and many previous versions of MM do do that. On the burn wizard Confirm Audio tracks page, there is a checkbox '[ ] Level volume' and a numeric dB control. Again though I wonder MM actual means by this numeric value, default 89dB - clearly not what is normally meant by CD volume level, i.e. a measure relative to the maximum, e.g. -22dB, the value typical for commercial releases of classical music.
Chris

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Re: What are target volume levels relative to?

Post by MMan » Sun Sep 06, 2009 1:57 pm

I have been slowly working on a wiki page on the topic of volume leveling and general information on converting analog to digital. While it is not yet ready for prime time, here is an excerpt relating to the issue or dB measures generally as well as how they relate to digital audio. As you correctly point out, dB is a relative scale, also a logarithmic scale.

The harder the air gets pushed, the louder the sound. Although this is typically referred to as volume, in reference to acoustical energy, it is called Sound Pressure Level (SPL). The scale used to measure Sound Pressure Level is the Decibel scale, or dB SPL.

The intensity of sound is measured in a unit called the decibel (dB), which describes the relative intensity of a sound based on a logarithmic decibel scale containing values ranging from 0 to 194. Although a zero value on the decibel scale represents the weakest sound audible to humans and sound intensity increases in correspondence with numeric values, the relationship among the values on the decibel scale is not linear but logarithmic. Therefore, the simple assumption that a sound with a 50 dB level is twice as intense as a sound with a 25 dB level would be incorrect. Rather, in a perfect world, each three decibel increment affects a 50% change in sound pressure levels. Thus, a 3 dB drop reduces sound exposure by 50%, while a 6 dB drop reduces exposure by 75%. Though reducing the decibel level produced by a sound source from 80 to 77 may not seem like a major change, it would actually represent a 50% reduction in audible sound.

The intensity of a sound reaching a person’s ear depends not only on the intensity of the sound produced, but also on the person’s distance from the source of the sound. If you were standing one foot away from a loud machine, for instance, you would experience higher decibel level than if you were ten feet away, even though the intensity of the sound produced remains unchanged. This is so because the intensity of sound decreases as sound waves spread out over time and distance, a behavior demonstrated by the Inverse Square Law. The Inverse Square Law is a calculable equation proving that each time the distance between the source of a sound and its recipient doubles, the recipient will experience a 6 dB drop in sound intensity, assuming that no surfaces are present to create reflections that in real world situations would alter these results.

dBFS - dB Full Scale

So sound is measured in dBs and the higher the dBs the louder the sound and these are typically positive values. So why when we start talking about dBs in digital music, are the values negative? First, it is important to remember that a dB is not an absolute measure, it is a relative measure. In most instances, it is a logarithmic function of the ratio of one measure to a reference standard. In the case of normal sound, as discussed above, it is the log of the ratio of the SPL measure of the sound to the weakest audible signal for the human ear (the reference standard).

In the case of digital music, the reference standard is the highest possible level digital gear can record, or 0 dBFS. All other measurements expressed in terms of dBFS will always be less than 0 dB (negative numbers). 0 dBFS indicates the digital number with all digits ="1", the highest possible sample. The lowest possible sample is (for instance for 16 bit audio): 0000 0000 0000 0001, which equals -96 dBFS. Therefore the dynamic range for 16-bit systems is 96 dB. For 20-bit digital audio it is 120 dB. For 24 bit digital audio it is 144 dB. Full-scale input level is the analog input voltage level that will cause the A/D converter to just equal full scale with no clipping on either positive or negative peaks.

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Re: What are target volume levels relative to?

Post by MMan » Sun Sep 06, 2009 2:12 pm

My last post didn't finish because something screwed up when I copied that in. Here is the rest of what I was going to say.

To your question, replay gain calculates the energy level of a file of -20 dBFS pink noise which would produce sound at 83 dB upon playback uisng the replay gain algorithm and uses that as a reference standard to compare against the calculation from the replay gain algorithm on the file being leveled. The 83 dB is the proposed standard. I'm not sure on the Monkey implementation, but I think that Monkey uses the target level input on the options page to replace the 83 dB. So if you have chosen 90 dB it calculates the value of the -20 dBFS pink noise file targeted to 90 dB and then compares that output to the output from the file being leveled to get the adjustment value. I am confident on the first part (see links below) but not sure on teh Monkey implementation. All that was a long winded way of saying that I think the target volume level is the level that a -20 dBFS pink noise file would playback at measured in SPL dBs. Hope this helps.

http://replaygain.hydrogenaudio.org/calibration.html

http://replaygain.hydrogenaudio.org/player_scale.html

chrisjj
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Re: What are target volume levels relative to?

Post by chrisjj » Mon Sep 07, 2009 7:46 am

A test shows they are seemingly relative to -98.57db (by the standard measure of from full scale).

Hence e.g. the default value 89dB means approx -10dB, standard.

(I took a 10Hz sine wave and did Level Track Volume to "89dB" - the results according to GoldWave was -9.57dB (from full scale).)

EDIT: This result is inaccurate because GW's measure is not Loudness but Average Volume:

http://facweb.northseattle.edu/nabdulla ... h%20Volume
Volume changes are based on a root-mean-square average, with silent regions excluded.
Chris

chrisjj
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Re: What are target volume levels relative to?

Post by chrisjj » Tue Sep 07, 2010 8:03 pm

Thanks MMan.
MMan wrote:I'm not sure on the Monkey implementation, but I think that Monkey uses the target level input on the options page to replace the 83 dB.
My tests confirm.
Chris

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