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Old 2nd January 2011
Lives for gear
kevin nowhow's Avatar

Question LKFS vs dBFS

Happy new year guys!

So i'm having this problem:i became familiar with the term "LKFS" just recently & i've given studying the ITU-R BS.1771 rec. a shot but still can't figure out how LKFS translates to dBFS!For example, would -23LKFS be the same as saying -23dBFS?If yes, what's the point of having one more abbreviation?If no, i could use some help with this subject...
Secondly, what's all this with LEQ(m),LEQ(a) e.t.c, e.t.c?
Last but not least:is LKFS the same thing as saying LUFS?

Thanx for yer time boys'n'girls!heh
Old 2nd January 2011
Gear Maniac

LKFS and DBFS are entirely different. LKFS and LUFS are pretty much "the same", except they are terms used by different standards groups. "Loudness, K-scale, below full scale" and "Loudness Units below full scale". A "LU", or loudness unit, is equivalent to one db. Both are in db increments, and when the same measurement process is used, the result is the same. For instance -23LKFS equals -23LUFS.

LKFS and LUFS will make much better sense when you actually work with a loudness meter.

"dbfs" is "decibels below full scale". "Full scale" is signal at, but not above, the point of "digital clipping". "dbfs" is often used to describe the levels of instantaneous peaks, but can also be used for various "weighted" peak readings, or even average/rms readings.

LKFS and LUFS are loudness measurements. Think of them as an rms (not peak) meter that becomes slower to react to level changes (higher or lower) for the longer you use it. It is basically a long term average reading of your audio. The more time you are measuring, the less important any particular instant becomes to the average. There is an equalizer ahead of this meter, too. The setting of the equalizer partially determines whether you are measuring leqA, leqM, or LKFS/LUFS.

There is something called "gating", which is a technique to suspend, or temporarily freeze, the measurement process, so you can sort of "skip over" some audio that you don't want to influence the result. Dolby used a technique called "Dialog intelligence" to measure only areas of program that contain dialog. This is "gating". A more recent method of gating is to suspend the measurement briefly when the program temporarily gets very quiet for a brief time. How this can be determined automatically is still being debated.

There is more to it, but I hope this helps clear up somewhat.
Old 2nd January 2011
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kevin nowhow's Avatar

Thanx a lot rfnoise!I have a fairly good understanding of VU metering & i can speak dBFS fluently(as i consider myself more of a recording studio person)but since i work in broadcasting these days i needed the other terms demystified.You surely founded a solid playground so i can focus my research at specific areas...
Old 2nd January 2011
Old 2nd January 2011
Gear Maniac

...and I forgot to mention that LKFS and LUFS are referenced to full scale digital even though they are technically power measurements. RMS is also a power measurement. So, a 1kHz -0dbfs sinetone will measure -3LKFS as well as -3rms. A 1kHz -20dbfs sinetone will measure -23LKFS.
Old 5th January 2011
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kevin nowhow's Avatar

Thanx fellas!See ya soon...
Old 25th July 2011
Here for the gear

Just want to clear something up here.... the "K" in the LKFS does not have any relation to Bob Katz's K-Scale metering - it refers to a "K-Weighting" filter that is placed in the programme chain prior to the metering calculator in an R128 compliant loudness meter.

This is not to denigrate Bob's work in any way, its just that the K is, in this case, referring to something a little different.

Not all K's are the same ;-)

Old 26th July 2011
Lives for gear

dBFS = deciBels with respect to Full Scale

LKFS = Loudness K-weighted with respect to full scale (in dB)

-23LKFS means that you applied K-weighting to your program material, made an rms measurement of the K-weighted material, and that the resultant is at -23 dBFS (relative) amplitude. LKFS is alleged to psychoacoustically correspond to the sensation of program loudness. dBFS does not correspond to any specific type of measurement or sensation.
Old 8th July 2015
Gear Nut
It's been a while, but I stumbled upon this thread in my own research of LKFS and LU and wanted to contribute this link:

Loudness Explained - Loudness | TC Electronic

Very helpful - sums up much of the previous posts but ties it all together really well.
Old 14th February 2018
Here for the gear

Originally Posted by kevin nowhow View Post

would -23LKFS be the same as saying -23dBFS?
Monitoring loudness (LKFS=LUFS) is VERY similar to RMS or VU (dBFS) monitoring with the difference being that LKFS loudness takes into account the ear and the brain's sensitivity to certain frequencies (fletcher munson curve)

I believe the algorithm to take into account dBFS plus frequency content of the material over time was developed by tc electronic.

Originally Posted by kevin nowhow View Post

Last but not least:is LKFS the same thing as saying LUFS?
They are the same now - LKFS (ITU/US standard) = LUFS (EU standard). At first the LKFS measurement included periods of silence or low loudness which lowered the measurement whereas the LUFS value ignored quieter parts below a gate threshold level. Currently the US and EU standards both incorporate a -10LKFS/LUFS gate level in their values so they are equal.

Here are a couple of resources that I have learned from:
LKFS/LUFS I discovered is now built in to Logic Pro 10.3+ and recent Adobe Premiere and Audition versions.

I discovered a couple of free loudness meter plugins as well:
Old 15th February 2018
Lives for gear

youlean has worked very well here/.
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