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Why do people keep throwing this RMS figure about?
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Babaluma
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22nd March 2012
Old 22nd March 2012
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Why do people keep throwing this RMS figure about?

Please forgive the rant, but I am getting really annoyed by people saying things like "aim for -10 RMS" etc. What do they actually mean by this? What are they using to measure their RMS? I ask because most RMS meters I have used give different readings on the same source.

My argument is that RMS figures, like the dB scale, are pretty meaningless unless you specify a lot of other necessary information (what software you are using to take the reading with what settings etc.), and that's without getting into the fact that RMS is not the greatest way to judge perceived loudness (it doesn't take frequency response or transients into account etc.)

I could give examples of many of the different ways to read RMS, but a simple one will suffice:

Let's say you are using the Elephant limiter, like me. If you say -10RMS and are using the "Pure" readout, but I'm using the "+3 AES" readout, then your -10RMS will be my -7RMS, quite a large difference.

Not really saying what is right or wrong here, just that people throwing these figures around is genuinely unhelpful, and that every time a client starts quoting these figures to me, I have to spend a long time explaining why they are pretty meaningless!
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22nd March 2012
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Q: Why do people keep throwing this RMS figure about?

A: Because they saw their favorite album show on the meters at given value
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Babaluma
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22nd March 2012
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Fair enough, then guess my question is, what meters? I usually use my ears to tell me when something sounds good or bad.

I just think it's clouding the issue, and unhelpful, to use RMS figures in the way that people seem to be using them recently. Was wondering if other people agreed?

Last edited by Babaluma; 22nd March 2012 at 02:16 PM.. Reason: Extra info
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We used to use VU meters (average reading meters). Above 0VU there was some predictable amount of headroom. Unfortunately, headroom is a lost concept in the modern digital world - but it is a large part of the sound of analog that everyone talks about.

What people mean by -10 RMS is that the average level of the mix (the root mean squared) is 10dB below full scale. It's a somewhat useful way of guessing the apparent volume of a track. There are plenty of meters that do not adhear to any specific spec, but AES 17 sets the standard that most averaging meters follow.

The bottom line: you can learn to correlate those numbers with what you're hearing in a calibrated system. I use VU meters for a quick glance at program levels. I generally don't read anything with a digital RMS display and would not find the number useful anyway. Others seem to find meaning in those numbers.

You can make good sounding recordings without knowing the RMS value.

GR
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22nd March 2012
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A 5-minute song can have a long piano passage at -20 and a short chorus peaking at -8 RMS.

Crest factor seems to be much more important...
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Babaluma
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22nd March 2012
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Thanks for all the input. Yes, I'm guessing that the Elephant "+3" mode on the RMS meter conforms to the AES 17 standard, but it seems most people are using it in "Pure" mode, which means the RMS figures they quote are actually different.

I've recently purchased a pair of Crookwood VU meters and they are great for reading average levels. With the standard calibration you have the "classic" level, and by switching the attenuator to -3dB you have something which closely approximates Mr. Katz's K-12 standard (-1 to +3 VU roughly corresponding to the "yellow" section on a K-12 meter).

And agree about the crest factor being more important. You could have a track that had been "bricked" and then had it's overall level reduced by 6dB, and it would appear low on an RMS meter, whilst actually sounding louder than full range dynamic material. Would be nice to see more meters giving an easy to read crest factor. I know you can just look at the distance between the peak and the average, but it's not always easy to see over any length of time. The best implementation I have seen so far was that hardware meter made by JLM in Australia for someone's Crookwood rack recently, the crest factor is very easy to see in red:

JLM Audio VUPPM Meter - YouTube
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22nd March 2012
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Quote:
Originally Posted by Babaluma View Post
Please forgive the rant, but I am getting really annoyed by people saying things like "aim for -10 RMS" etc. What do they actually mean by this? What are they using to measure their RMS? I ask because most RMS meters I have used give different readings on the same source.

My argument is that RMS figures, like the dB scale, are pretty meaningless unless you specify a lot of other necessary information (what software you are using to take the reading with what settings etc.), and that's without getting into the fact that RMS is not the greatest way to judge perceived loudness (it doesn't take frequency response or transients into account etc.)

I could give examples of many of the different ways to read RMS, but a simple one will suffice:

Let's say you are using the Elephant limiter, like me. If you say -10RMS and are using the "Pure" readout, but I'm using the "+3 AES" readout, then your -10RMS will be my -7RMS, quite a large difference.

Not really saying what is right or wrong here, just that people throwing these figures around is genuinely unhelpful, and that every time a client starts quoting these figures to me, I have to spend a long time explaining why they are pretty meaningless!
I hear you!

And besides differences in standards, it seems like every RMS meter uses a different RMS window size yielding different readings.

I brought this up before: How do YOU measure RMS?
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Babaluma
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22nd March 2012
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Ah, thanks for the link!

My main meters are the Sonoris Meter, Voxengo Elephant and Span, and the RME Digicheck software. I've managed to get them all conforming to the same "standard" in my system, only trouble is it doesn't seem to correspond to the various ones many other people are using!
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22nd March 2012
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@Babaluma

Just look here for Toscanalyzer, a free tool to measure RMS.

Just load some audio files into the application and start "Reports->Key value Report". It shows many parameters including RMS, Peak, and dynamic index packed in a nice looking table.

And you are right: pure RMS does not say anything, the dynamic of song is the salt in the soap :-)

br
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22nd March 2012
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Quote:
Originally Posted by Greg Reierson View Post
We used to use VU meters (average reading meters). Above 0VU there was some predictable amount of headroom. Unfortunately, headroom is a lost concept in the modern digital world - but it is a large part of the sound of analog that everyone talks about.

What people mean by -10 RMS is that the average level of the mix (the root mean squared) is 10dB below full scale. It's a somewhat useful way of guessing the apparent volume of a track. There are plenty of meters that do not adhear to any specific spec, but AES 17 sets the standard that most averaging meters follow.

The bottom line: you can learn to correlate those numbers with what you're hearing in a calibrated system. I use VU meters for a quick glance at program levels. I generally don't read anything with a digital RMS display and would not find the number useful anyway. Others seem to find meaning in those numbers.

You can make good sounding recordings without knowing the RMS value.

GR


I use VU's , and proud of it,
Babaluma
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22nd March 2012
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Quote:
Originally Posted by tom_toscanalyzer View Post
@Babaluma

Just look here for Toscanalyzer, a free tool to measure RMS.

Just load some audio files into the application and start "Reports->Key value Report". It shows many parameters including RMS, Peak, and dynamic index packed in a nice looking table.

And you are right: pure RMS does not say anything, the dynamic of song is the salt in the soap :-)

br
-tom
Thanks, downloading it now and will have a look tomorrow. There's also the Orban Loudness Meter, but it doesn't work with my ASIO drivers.

Last edited by Babaluma; 22nd March 2012 at 09:33 PM.. Reason: Quote
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I'm also loving my VU meters, never seen anything digital that even comes close!
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22nd March 2012
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Quote:
Originally Posted by Virtalahde View Post
Q: Why do people keep throwing this RMS figure about?

A: Because they saw their favorite album show on the meters at given value
And so if you match the RMS values, it will sound great.

Easy enough!


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22nd March 2012
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Quote:
Originally Posted by dcollins View Post
And so if you match the RMS values, it will sound great.

Easy enough!


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22nd March 2012
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My take is that we humans don't have sensitive enough ears to hear peak values clearly.
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22nd March 2012
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Quote:
Originally Posted by ksandvik View Post
My take is that we humans don't have sensitive enough ears to hear peak values clearly.
Exactly, which is why watching peak meters tells us very little about the sound of the signal we're looking at.

GR
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Folks like to quantify and qualify ; Look at dichotomus thinking .... you then deal with a very complex world with less effort when you simplify ...


That's my favorite catagory in JEOPARDY :


" Wide and sweeping generalzations for a thousand , Alex"




SO the simple answer is ; just hire a monkey with a limiter to make your 2X4 's RMS -5 and yer good to go !!!
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23rd March 2012
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23rd March 2012
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23rd March 2012
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[sarcasm]Probably because it means something important.[/sarcasm]


As much as I don't like 1770, it's better than nothing.

And, flatfinger, yeah, like you said!
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Not a pro but I would assume that:

1) They are talking about the absolute DBFs. If your meter is calibrated to -3/10/12/14/ then you obviously need to add that up. If I aim for 8dbfs then I do probably calibrate the meter to -8 and aim to 0rms.

2) That should only apply when the music is peaking at 0dbfs. So what is really meant is a crest factor of 8db.

3) RMS size of 250-500ms is used. Some may take the average of a whole track but I don't think that makes too much sense. When the meter stays at around 8rms when the loud passage is played that is what is meant with aim for 8rms.

Most people probably figured these are rather obvious thing so no need to explain them when the same thing can be said in much more convenient way.
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@Oden
Quote:
Originally Posted by Oden View Post

3) Some may take the average of a whole track but I don't think that makes too much sense.
hmm, if you need to go for a K14 master, then you have to look at the RMS average...

br
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23rd March 2012
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Quote:
Originally Posted by j_j View Post
As much as I don't like 1770, it's better than nothing.
As a perceptual model? As a concept? How about related meta level systems for audio streaming like Sound Check and Replay Gain?

GR
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24th March 2012
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Quote:
Originally Posted by Greg Reierson View Post
As a perceptual model? As a concept? How about related meta level systems for audio streaming like Sound Check and Replay Gain?

GR
It's fine for sounds that are already radio-processed and squashed flat. No more am I going to say, I've gotten too much flack from folks who like "simple" despite the obvious flaws.

If and when you read about the validation test, please ask what the material was, and drill in a bit to find out where it came from, and how it was treated, etc.
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Quote:
Originally Posted by j_j View Post
It's fine for sounds that are already radio-processed and squashed flat. No more am I going to say, I've gotten too much flack from folks who like "simple" despite the obvious flaws.

If and when you read about the validation test, please ask what the material was, and drill in a bit to find out where it came from, and how it was treated, etc.
Actually, I can understand how a complicated, committee-derived, loudness model has problems.

It's how RMS became a 'figure of merit' in mastering that has me confused......

Where did it start?


DC
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Quote:
Originally Posted by dcollins View Post
Actually, I can understand how a complicated, committee-derived, loudness model has problems.

It's how RMS became a 'figure of merit' in mastering that has me confused......

Where did it start?


DC
Before anyone knew how to even think about measuring loudness, frankly, at the dawn of electrical devices. It works for resistors, after all. (Yes, I actually had somebody say that to me when discussing loudness of very low frequencies.)
Babaluma
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24th March 2012
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Quote:
Originally Posted by dcollins View Post
It's how RMS became a 'figure of merit' in mastering that has me confused...... Where did it start?
Dave, as usual you've hit the nail on the head in a simple sentence. This is exactly what I meant with my original post. Why are people throwing these figures around like they actually mean something that makes scientific sense?
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Quote:
Originally Posted by Babaluma View Post
Dave, as usual you've hit the nail on the head in a simple sentence. This is exactly what I meant with my original post. Why are people throwing these figures around like they actually mean something that makes scientific sense?
I assume Bob's book has something to do with it? I frequently see RMS readings posted here in relation to a K setting, but I don't really know where it was incorrectly popularized.

It's a good system for measuring the total energy in a waveform, that RMS, but for talking perceived level....................


DC
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25th March 2012
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I think a lot of it is driven by people wanting to avoid the need for a human being actually listening and making the appropriate adjustments, i.e. about reducing labor costs.
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For some reason I'm suddenly reminded of how the local municipality claimed that they were going to train the police to know when someone was breaking the noise ordinance because they'd be schooled on how to recognize the difference between 60dbA and 70 dbA. So I brought a meter into town hall and asked the baliff to arrest everyone...

Yeah unrelated but CSB!

/the new noise ordinance did not pass after that I win :P
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