RMS vs. VU

Archived from groups: rec.audio.pro (More info?)

thanks guys...

i don't really worry about peak levels too much as i have been
given a maximum level of -10 dBFS (i brick-wall my final mix at -10),
with a 0 VU reference level of -20 dBFS. i do find it very interesting
to visually monitor
my peak-to-average levels.

i've been mixing spots for TV for 7+ years, so i'm no stranger to
this environment. i just never had "quality" metering, and i really
want to get as good as i can as an audio post mixer. my program
material is voice and music and it airs on our local PBS station. it
is
a documentary/entertainment type show.

thanks again,
marty.

Archived from groups: rec.audio.pro (More info?)

In article <1117827395.492200.221700@f14g2000cwb.googlegroups.com> cheetah@tequilamockingbird.com writes:

> so i'm mixing a TV show and using Spectrafoo for my metering.
> my meter shows VU and RMS, though i must admit i'm not
> positive yet i have it configured correctly. which one of
> these values should i be more concerned with as it relates
> to "loudness" and consistency in the broadcast chain?

Well, I've been wanting to add SpectraFoo to my tool kit for a long
time now, but since they continue to not make a Windows version, I
don't have any personal experience with it. However, I'll make an
educated guess that these have to do with how the meter looks
visually. A proper VU meter (and I believe that SpectraFoo does a good
job of emulating one) is specified to have a particular rise and fall
time in response to a step change in level. So if you set it to VU,
I'll bet that on program material, the action of the virtual meter
pointer looks pretty much like that of a real VU meter. If you set it
to RMS, my guess is that it has a different time constant, but I don't
know if it's faster (which would show peaks closer to their actual
value) or slower (which might do the opposite).

Which to use depends on what your program material is, and if you're
working to analog or digital medaia. If it's modern music, I'd go with
RMS response. If it's speech, definitely go with VU. Digital is more
fussy about knowing where the maximum peak level is. I suggest asking
your customer, but I suspect that if you did, he'd say "Huh??"

Unless you find that you get a substantially different mix level when
watching the meter set one way or the other, I'd just go for whatever
you like. I'd probably use VU. I still use VU meters when mixing to a
digital recorder and they work fine for me.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

Archived from groups: rec.audio.pro (More info?)

On 6/3/05 3:36 PM, in article
1117827395.492200.221700@f14g2000cwb.googlegroups.com, "marty lester"
<cheetah@tequilamockingbird.com> wrote:

> hey out there-
>
> i did a brief search in the archives, but didn't see what i'm after...
>
> so i'm mixing a TV show and using Spectrafoo for my metering.
> my meter shows VU and RMS, ... which one of
> these values should i be more concerned with as it relates
> to "loudness" and consistency in the broadcast chain?
>
> in other words, is RMS or VU more critical for broadcast
> mixing?
> am i correct in my assumption that VU is average RMS?

NO.

Both are averaging meters, but there are many ways to choose how you
determine average

RMS is a real mathematical average level computation.
VU is a VERY specifically defined (in the 1930's) special case mechanical
response that makes a meter needle respond in a SPECIFIC visually useful way
on SPEECH material to attempt (pretty successfully) to show relative
LOUDNESS of the program in a visual manner. It's handy and useful if you
know how to interpret it.
RMS might well be a more useful type of monitoring aid, combined with a
peak-meter to make sure you;re ok there.
"critical for broadcast"?
A good consistant listenign level that doesn¹t go over.
You can achive this with your ears and a peak meter, or any number of ather
types of meters out there.
The Dorroughs are nice
Spectrafoo has MANY options there, Play and experiment and compare and
contrast all of them to get a better handle on what you need to know by ear
as you stay in the biz.

Archived from groups: rec.audio.pro (More info?)

On 3 Jun 2005 12:36:35 -0700, "marty lester"
<cheetah@tequilamockingbird.com> wrote:

>hey out there-
>
>i did a brief search in the archives, but didn't see what i'm after...
>
>so i'm mixing a TV show and using Spectrafoo for my metering.
>my meter shows VU and RMS, though i must admit i'm not
>positive yet i have it configured correctly. which one of
>these values should i be more concerned with as it relates
>to "loudness" and consistency in the broadcast chain?
>
>in other words, is RMS or VU more critical for broadcast
>mixing? i'm pretty sure i'm getting my terms and values
>mixed up, so if anyone wants to school me in simple terms
>how VU and RMS relate, i'd appreciate it. am i correct in
>my assumption that VU is average RMS? not sure where i got
>that from...
>
>until i got Foo running, i was using an old cassette deck's
>VU meters for my metering. i must say i love Spectrafoo,
>if i can only get my head totally around it.
>
>thanks in advance,
>marty.

If what interests you is keeping close to, but not over a peak limit
for the TV modulator, use PPM, not VU.

d

Pearce Consulting
http://www.pearce.uk.com

Archived from groups: rec.audio.pro (More info?)

>RMS is a real mathematical average level computation
===========================
No, thats's an average. RMS is the square root of the mean (that's the
average) of the square of the input voltage. (That's the power). RMS is
a couple of dB higher than arithmetic average for speech... the
'peakier' the waveform, the higher the rms will be above the average.
RMS is the 'DC equivalent' voltage that heats the voice coil the same
amt. DBX limiters used rms levels because 'that's what the ear hears'.

Archived from groups: rec.audio.pro (More info?)

On 6/3/05 6:47 PM, in article
1117838861.348121.56290@g49g2000cwa.googlegroups.com, "marty lester"
<cheetah@tequilamockingbird.com> wrote:

> thanks guys...
>
> i don't really worry about peak levels too much as i have been
> given a maximum level of -10 dBFS (i brick-wall my final mix at -10),
> with a 0 VU reference level of -20 dBFS. i do find it very interesting
> to visually monitor my peak-to-average levels.
>
> i've been mixing spots for TV for 7+ years, so i'm no stranger to
> this environment. i just never had "quality" metering, and i really
> want to get as good as i can as an audio post mixer. my program
> material is voice and music and it airs on our local PBS station. it
> is
> a documentary/entertainment type show.

Then you;re way ahead... Just play around and choose what you like to watch
the most.

Archived from groups: rec.audio.pro (More info?)

In article <1117838861.348121.56290@g49g2000cwa.googlegroups.com> cheetah@tequilamockingbird.com writes:

> i don't really worry about peak levels too much as i have been
> given a maximum level of -10 dBFS (i brick-wall my final mix at -10),
> with a 0 VU reference level of -20 dBFS.

That's a SMPTE standard, so you've been given good guidance. I
wouldn't depend on a brick wall limiter to give you your maximum
level, though. Just use it to protect yourself.

> i do find it very interesting
> to visually monitor my peak-to-average levels.

That lets you visualize how loud it actually sounds. Assuming the
peaks go as high as you're allowed, an RMS level close to the peak
level will sound loud, while an RMS level considerably lower will have
more dynamic range. (as a general rule)


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

Archived from groups: rec.audio.pro (More info?)

marty lester <cheetah@tequilamockingbird.com> wrote:

> hey out there-
>
> i did a brief search in the archives, but didn't see what i'm after...
>
> so i'm mixing a TV show and using Spectrafoo for my metering.
> my meter shows VU and RMS, though i must admit i'm not
> positive yet i have it configured correctly. which one of
> these values should i be more concerned with as it relates
> to "loudness" and consistency in the broadcast chain?
>
> in other words, is RMS or VU more critical for broadcast
> mixing? i'm pretty sure i'm getting my terms and values
> mixed up, so if anyone wants to school me in simple terms
> how VU and RMS relate, i'd appreciate it. am i correct in
> my assumption that VU is average RMS? not sure where i got
> that from...
>
> until i got Foo running, i was using an old cassette deck's
> VU meters for my metering. i must say i love Spectrafoo,
> if i can only get my head totally around it.

The PPM system was the result of a great deal of research into the best
way of monitoring levels for broadcast and of relating subjective sound
levels to objective transmitter requirements.

You may find a PPM feels a little strange at first if you have never
experienced anything other than VU-type meters, but it is actually very
informative and a lot easier to read, once you get used to it.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

Archived from groups: rec.audio.pro (More info?)

On 6/4/05 1:04 AM, in article
1117861442.830034.223910@o13g2000cwo.googlegroups.com, "BobG"
<bobgardner@aol.com> wrote:

>> RMS is a real mathematical average level computation
> ===========================
> No, thats's an average. RMS is the square root of the mean (that's the
> average) of the square of the input voltage. (That's the power). RMS is
> a couple of dB higher than arithmetic average for speech... the
> 'peakier' the waveform, the higher the rms will be above the average.
> RMS is the 'DC equivalent' voltage that heats the voice coil the same
> amt. DBX limiters used rms levels because 'that's what the ear hears'.
>

Badly phrased I was being.. All I meant was that RMS is a real
mathematically-calculated value... An 'average' rather than The mathematical
'Average' whereas VU is a mechanical-movement-based concept.