Subject:Reference tone (and all audio) always 6db hotter. Why?

Posted by: EdZeke

Date:12/3/2004 4:45:03 PM

Can someone explain what's happening here?

Sound Forge always seems to import and create audio files that are 6db hotter than they are in other sound/video apps. If I create a 1k tone at -12db in another app (not Sound Forge), when I import it into Sound Forge the same tone is always 6db hotter (-6db on the level meter instead of the -12db that it was originally created at). The reverse is true going the other way; when I export a -12db 1k reference tone from Sound Forge, other audio/video apps see it as 6db softer (-18db on its levels meter).

I understand that sound volume is halved every -6db and doubled every +6db. Can someone explain this? I am using digital files and digital levels excusively on a computer. There is no analog conversion or monitoring. I really need to figure this out.

Thank you!

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: MJhig

Date:12/3/2004 4:54:13 PM

Hmmmm, I regularly go between Sound Forge 6, Vegas 4 and Sonar 2.2 XL and never see a difference in the dBFS. Not to mention other players that never seem to clip when the file is often at 0 dBFS.

What "other" app/s. are u talking about?

MJ

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: ATP

Date:12/3/2004 5:44:07 PM

hmm interesting. my experience with SF levels is a bit similar. files that are normalized to 0 db in SF will clip on the faders of a DMX-R100 mixer wired to a HD recorder. i always thought the mixer was a bit off, since i hear no digital clipping at all through the monitors.

i don't use any other audio editing tools though, so i can't check it against other software.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/3/2004 7:15:46 PM

Thank you for responding. The 'other' app that I am referring to is Final Cut Pro. Yes, this is Mac software and Sound Forge is a PC app. But that shouldn't matter when dealing with a standard .aif or .wav file. FCP inputs the file at the correct db. It's when it goes to Sound Forge or from Sound Forge that the audio file is either 6db above or 6db below what it 'should' be. Doesn't seem to matter whether the tone is generated on the Mac or PC side. It is very strange and repeatable on my system as well as completely different systems.

Any ideas? I just want to know what's happening here. I realize there are easy workarounds for this (i.e. run the audio through a batch processor and alter the levels or export from SF 6db higher than I normally would).

Thanks again,

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: jorgensen

Date:12/6/2004 12:48:06 AM

You are measuring the peak value, and the recording level is RMS.
That's how it should be.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/6/2004 6:13:50 AM

Would you mind explaining this a bit more please?

Thank you,

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/6/2004 8:15:35 AM

Jorgensen is refering to the difference in an RMS meter vs a peak meter. Since I don't use FCP I'm not sure what type of meter it has in it. Actually the RMS value of a sinewave is always -3dB lower than it's peak Value and you're seeing a 6dB difference. First of all let's back up a little and tell us how you're getting these values in the first place in each app? There are 2 types of meters in Sound Forge, one is a peak meter and the other is a VU/PPM meter. Which are you referring too when you list your values. If FCP has a peak meter, then the values should be the same as on Sound Forges peak meter.

If you generate a Sinewave in Sound Forge and set the "amplitude" adjustment to -6dB, then this is the maximum "peak" value that the sinewave will display. Thus when you playback that sinewave, you will see Sound Forge's peak meter read -6dB as it should. After you generate this sinewave, select the entire waveform and goto TOOLS>STATISTICS. The Statistics will show a maximum sample value of -6dB, and the RMS Power will be -9dB. If you export that sinewave as a .WAV and then import it into FCP, then these should be the same values that FCP shows on a "peak" meter, as long as all fader adjustments in FCP are set to 0dB.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/6/2004 10:42:27 AM

Thank you for you in-depth response. Although I'm not an 'audio guy,' I think I understand what you're saying. I will try what you're suggesting.

But not only am I getting a visible 6db difference, I am also getting an obvious audible difference. The clip is in fact louder (6db) than the original. Would your explanation account for that too?

Thanks.

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Sonic

Date:12/6/2004 1:43:40 PM

Check your faders and routing in FCP. It's likely playing back at some default trim that Sound Forge doesn't apply or perhaps there is a channel conversion going on somewhere.

What you see in Sound Forge is the "real" dBFS level, no gain applied anywhere.

Another possibility, if it is a mono file, Sound Forge attempts to open the hardware as mono, which leaves routing behavior up to the driver. Most do what you'd expect (just pipe it to both sides). Some do other things.

J.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/6/2004 5:00:17 PM

Hmm. Thanks again for the reply. I am doing some tests and learning a lot about the fundamentals of audio. So, in a way, this is all good for me.

The files that seem to get doubled (6db 'added') are in fact mono files. They are recorded as -12db (ref) mono .aif files. When imported into SF they gain 6db because from what I've been reading SF automatically creates a stereo track out of mono files (or at least seems to treat them like stereo).I understand that earlier versions of SF did not do this. I am using SF 7.

Does this sound correct?

Thank to everyone for your input.

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/7/2004 5:41:39 AM

If you guys out there have 5 minutes to try a little experiment it might confirm what I'm talking about. Generate a MONO -12db reference tone in an application OTHER than Sound Forge. Then bring it into Sound Forge 7 and see what happens. I am willing to bet that you will see and hear 6db added to the tone making it read -6db on the meter instead of -12db.

From what I have been reading on other people's posts is SF is 'primarily and only a stereo audio application' and 'that versions 4 and older didn't have this issue with mono files.'

Sounds hard for me to believe too. Please let me know your findings.

Thank you all,

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/7/2004 6:55:03 AM

I created a mono sinewave that was peaking at -12dB in wavelab v3.0. Peak meter in wavelab read -12dB. Saved the file as .wav and opened it in Sound Forge 7.0. Sound Forge opened it as a mono file. When played back in Sound Forge it showed -12dB on the peak meters. Tried the same thing this time saving as an .AIF format in Wavelab and then opening it in Sound Forge same results as .WAV. I have another PC that has Sound Forge 7.0 and Cool Edit Pro, that will be able to do the same test and am expecting the same results, I will let you know.

Have you checked all the fader levels in FCP? Are they all set to 0dB as I previously mentioned? Do you have any other programs to open the file in and play it, to check the levels? Which sound card are you using? What are the sound cards driver mixer settings? Are they set at 0dB? Are you routing the sinewave to any other buses in FCP other than the master bus? What is the Master buses level readin in FCP? When you open the file in Sound Forge and goto TOOLS>Statistics, What is the Maximum sample value in Statistics?

If you can answer all the questions I posted above, we can tell you where the problem is. Right now I can tell you the problem is not in Sound Forge.

Sound Forge is not primarily a Stero editor. It has always edited mono as well as stereo files and I have used every version of Sound Forge since v4.5 through v7.0

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/7/2004 8:02:22 AM

Rednroll, thank you so much for assisting me with this. I really do appreciate it

Great questions. I will try to answer them in a bit but first let me give you a little back story. This 'issue' has plaqued me for a very long time and on different systems. When I do a remote VO session with someone, the talent ususally records their own session and FTP's the files to me. What they give me is a -12db mono .aif file. Not sure what hardware/software they use. I could ask but it's several VO people. Not that it matters either but most likely they are using a PC. These files are then going directly to SF for editing, never touching a Mac or FCP. The levels in SF are consequently -6db and obviously louder (no distortion) than intended. These VO's run underneath graphics (not video) that end up on a CD-ROM.

FCP comes into play because all of the video segments on these CD-ROM projects are edited using FCP. As you can imagine when placed next to each other on the CD-ROM the -6db VO's are twice as loud as the -12db FCP videos.

I have been using the FCP/SF combination to do my testing and have discovered that when I output a stereo -12db file from FCP and import it into SF it is read perfectly fine. But when I export a mono file from FCP and import it into SF it is 6db hotter. So it would seem to me that it is a mono/stereo issue. AND I have been reading several other people's posts that seem to confirm that SF 'does something' to mono files (duplicating the sound in one channel to the other thus doubling it's volume hence -6db). The reverse is true if I go the opposite direction. A stereo file exported from SF and imported into FCP is perfectly fine whereas a mono file exported from SF and imported into FCP the levels are 6db LOWER (-18db). So again it seems like it's a mono/stereo issue. As if SF is consistently duplicating the audio (mono only) in one channel into the other channel.

I completely respect your input and comments. I'm just trying to give you some info from my end to chew on.

Now to try to answer your questions:
1. The faders in FCP are at 0db and the level meter indicates a -12db level when that's what I try to make.
2. I don't think I have another Mac program to check the levels but I can probably find one.
3. I am not using a particular sound card in the Mac, just the built-in audio in a Powermac G5 dual 2.5. In the PC, not sure. It's not a 'special' a/v PC. A run-of-the-mill desktop.
4. No other routing in FCP.
5. Master bus is at 0db.
6. In SF's TOOLS>STATISTICS, The -12db mono FCP generated sound reads 'Maximum Sample Value 16,422 (-6.00db, 50.12%).'

Apparently, according to other posts I've read, SF 4 and below don't do this to mono files. You said you've used version 4.5 through 7. I mean no offense here but is it possible then that you just might not have noticed this 6db addition to mono files?

Thank you for helping me to get to the bottom of this.

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Sonic

Date:12/7/2004 8:27:32 AM

"What they give me is a -12db mono .aif file."

-12 dBFS, -12 dBVU, -12 dB RMS?

"The levels in SF are consequently -6db and obviously louder (no distortion) than intended."

You mentioned before that Sound Forge opened these as stereo files. Is that really the case? If so, either the file header is really stereo or you may have the "Merge L/R to stereo" option checked in the Open dialog.

"But when I export a mono file from FCP and import it into SF it is 6db hotter"

Sounds like FCP renders a stereo project to mono by summing channels to me. Can you specify a mono project/master in FCP?

"I have been reading several other people's posts that seem to confirm that SF 'does something' to mono files (duplicating the sound in one channel to the other thus doubling it's volume hence -6db)"

Horse hockey. It does no such thing. Where are these threads? On mono file playback Sound Forge opens the device with a mono format. As I mentioned before, some drivers do unexpected things here, but most just pipe it to both sides as you'd expect. If you were expecting it to come out of only one speaker, then the SPL hitting your ears is 6 dB louder, but that makes no difference on the peak meter, which is driven by the (mono) data being sent into the hardware.

"...whereas a mono file exported from SF and imported into FCP the levels are 6db LOWER"

Again, sounds like an FCP issue.

But you don't have to take my word for it. As Rednroll implied, if you introduce a third application, the source of the problem should be fairly easy to isolate.

J.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/7/2004 9:25:00 AM

"What they give me is a -12db mono .aif file."

"-12 dBFS, -12 dBVU, -12 dB RMS?"

This is a very good point that Sonic makes. If you are receiving something that says -12dB, this means nothing unless they give a value along with it. So far in this discussion, we've been referring too -12dBFS, which is the same as saying -12dBpeak meter reading. If they wrote -12dBVU, then we're in a whole different discussion.

FYI, I did the same test with generating a -12dBFS sinewave in Cool Edit Pro v2.0 and then saved it to both .aif and .wav formats and saw the same results in both CEP and Sound Forge 7.0. Both apps read -12dBFS when played back.

"I have been reading several other people's posts that seem to confirm that SF 'does something' to mono files (duplicating the sound in one channel to the other thus doubling it's volume hence -6db)"

You are unneccessarily confusing topics that really don't relate to your problem. What you have probably read is the way Sound Forge handles mono files, when placing stereo FX's in the plugin Chainer. Sound Forge will keep the file MONO although you may be running it through a Stereo FX. What you probably read is that you need to make the mono file stereo by copying the data to Left and right channels, so the mono file can be processed in stereo through the stereo plugin.

Sound Forge does not automatically copy the mono file to Left and Right. It plays the mono file through the meter and the output, so the same level is played out both speakers and both peak meters. Thus if you have a -12dBFS mono sinewave, it will send this sound to both the left and right outputs at -12dBFS, thus the right and left peak meter will both read -12dBFS.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/7/2004 9:37:00 AM

You guys are awesome. Thank you!

O.K. I'll try to get you a little more info to work with. These .aif files that are given to me by the VO talent (again, not sure how they create them) are -12db mono files. When opening in FCP they are -12db mono files. When opened in SF they are also mono (single channel) files but at -6db. How do I answer your first question? I am not an audio expert (obviously). Maybe the answer to this question will clear it all up?

I cannot specify, per se, a mono project/master in FCP but I can certainly make the audio mono by either eliminating one of the channels altogether and center panning that remaining channel (or not).

I'll try to find these threads again. Maybe I wasn't understanding them or maybe they are flaky users.

5th paragraph down:
http://www.proaudioreview.com/par/april03/sonicfoundry.shtml
http://palimpsest.stanford.edu/byform/mailing-lists/arsclist/2004/06/msg00162.html

These certainly don't say much but thought it was kinda pointing me to something. There were other posts but, unfortunately, I can't find them now. These are unimportant anyway.

I have used a third party app (on the Mac) to create reference tone. It's called Pure Tone. I create a 1k, 1 channel, tone at 1/2 amplitude (.50). FCP reads this as a single channel yet center panned -12db clip. SF reads this as a single channel, center panned -6db clip. Again, this is exactly what happens when I receive the VO audio files from the VO talent.

Maybe someone out there can generate a 10 second ,-12db, mono tone file that I could download to test in FCP as well as SF?

Thanks.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/7/2004 10:00:45 AM

"It's called Pure Tone. I create a 1k, 1 channel, tone at 1/2 amplitude (.50)"

This should tell you where the problem is and it's in FCP. "1/2 amplitude, is 1/2 of 0dBFS, which would be -6dBFS, thus 6dB is half of full scale. .25 amplitude is -12dBFS. Thus Pure tone is creating a -6dBFS mono sinewave, exactly what Sound Forge is telling you it is.

It sounds like exactly what you're saying Sound Forge is doing, is what FCP is doing. In FCP if it does allow you to open Mono files directly. It sounds like it's taking a mono file and using the pan law, and then subtracting -6dB and displaying -12dB out both meters. This is a common pan function, known as "Balance -6dB center", thus you are reading -12dBFS for a -6dBFS mono sinewave, due to the Pan function subtracting -6dB. If you fully send the Pan to either left or right, you should see the meter read -6dB for this file you are referring too. If FCP has different Pan modes, you should switch the pan mode to something like "Balance 0dB center" and this will display the samething as Sound Forge when the pan is set to center.

I don't have a MAC, so I don't have access to FCP. I recommend you download Bias PEAK for the MAC which has a 14 day full trial demo and let us know what you see in that app. It should be very similar to what you are seeing in Sound Forge.

Go here: www.bias-inc.com and download the trial of Peak for the MAC and this shouldn't have the Pan problems that FCP introduces and will show you the same thing Sound Forge is showing you.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/7/2004 10:35:12 AM

All of this sounds correct. Excellent explanation. Again, thank you. BUT, the files that I receive from the VO talent are generated at a -12db reference. Without touching the Mac or FCP, SF imports them in at -6db. The file appears to be single channel but pan centered in SF as I see only one channel and I see a -6db level in both sides of the meter. So let's forget about FCP for the moment but I understand what you're saying.

I have put a reference tone clip on my FTP. FCP reads it as mono, pan centered at -12db. SF reads it as mono, pan centered at -6db. Feel free to download it and see if your SF reads it the same way and also feel free to upload a -12db reference tone for me to try.

Via a web browser:
http://edzeke.mine.nu:1987
name: audio
pass: test63

Via an FTP app:
edzeke.mine.nu
same name and pass

Thank you!

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/7/2004 11:47:18 AM

I downloaded this file, it is indeed a -6dBFS mono sinewave. This basically leads us back to their labeling of the file of either it's dBvu,dBFS or dBrms. Like I mentioned a -6dB center position pan is common and they maybe doing the same thing in their app as you are doing in FCP, by playing it back through a pan control that subtracts -6dB when the pan is in the center position. I checked this file in 5 different apps and got the same result of it being a -6dBFS mono sinewave and they all displayed the file as -6dBFS on their meters. Those being Sound Forge 7, Sound Forge 4.5, Traxtion, Nuendo, and Cool Edit Pro.

Sound Forge is not wrong, the people who are sending you the file as a reference tone are incorrectly labeling it. Usually, this type of tone is used for setting up VU meters, where they use a -12dB sinewave and play that back and you adjust the inputs on your analog devices so they read 0dBVU on your meters. This is a common practice to keep levels the same when recording audio and tranfering it from studio to studio. The problem is, that this will be wrong because this is not a -12dBFS sinewave as they indicate. Unfortunately, they are making a mistake by mislabeling due to they are playing it back through an app, that probably uses the -6dB center balance Pan law and are assuming you will be doing the same thing or are doing this unknowingly.

In any case I uploaded a -12dBFS mono sinewave for you.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/8/2004 6:21:59 AM

Thanks for testing my tone file and thanks for uploading yours. In conclusion, it sounds like to me what's happening here is:

To reiterate. A stereo file does not produce these effects at all. Everything gets along great between apps.

Using a -6db mono 1k clip:

SF 1/2's the amplitude and then copies the audio in the mono channel and duplicates it into the other channel thus doubling the volume again bringing it back to -6db. Essentially, SF is preserving the db attribute but 'kinda' making a stereo sound from the mono sound.

FCP sees the mono clip and center pans the audio thus dropping the amplitude in each channel to -12db. Preserving the mono attribute but lowering the volume.

These are the effects anyway. Now to figure out what the best 'fix' is. My goal is to get the SF edited VO clips to match the FCP edited videos without futzing with levels.

Thank you for all of your help.

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/8/2004 8:01:35 AM

"SF 1/2's the amplitude and then copies the audio in the mono channel and duplicates it into the other channel thus doubling the volume again bringing it back to -6db. Essentially, SF is preserving the db attribute but 'kinda' making a stereo sound from the mono sound."

This is incorrect. Sound Forge does not 1/2 the amplitude. The amplitude of the -6dB sinewave you have is -6dBFS (FS=Full Scale). This is a mono signal, thus there is only one channel as opposed to 2 in a stereo file. So rather than routing the single channel to the left or to the right, which would be odd, because the sound would then only be coming out of your left or right speaker, Sound Forge routes this signal to both the left and right output when playing a mono file. Thus the -6dBFS signal is playing out the left speaker and the right speaker, and when you look at the sound Forge Left/Right peak meters, you will see that both of them are moving together and are identical, where they are both reading -6dB. So nowhere in there was anything halved or added together. The signal started at -6dB and ended at -6dB and this is visually sown to you on the peak meters.. When I previously asked you to run the "statistics" tool on the waveform and you told me the max sample value was -6dB, alls soundforge does is scan through each sample and find the maximum sample value, which will also be your max Peak meter value when the file is played back.

"FCP sees the mono clip and center pans the audio thus dropping the amplitude in each channel to -12db. Preserving the mono attribute but lowering the volume."

Not exactly. When you place a mono file in FCP, the pan position is defaulted to the center, so that again your single channel mono file will be routed to the left and right speakers. To prevent center channel build up caused by panning mono signals to the center, FCP will reduce the signal by -6dB, when and only when that pan is in the center position. So FCP routes it to both the left/right outputs like soundforge, but then reduces each output by -6dB due to the pan position. So the signal started at -6dBFS as it did in Sound forge, it got routed equally to the Left/right outputs as it did in Sound Forge ,which would make it show -6dBFS in both the L/R peak meters, but then due to the center Pan position it subtracts -6dB from each side, thus displays -12dBFS on the meter. That is the ONLY difference and it is due to the pan control position in FCP. I previously asked you to put the Pan either hard left or hard right. Did you do that? If you did here;s what you should have saw. So let's say you turn the pan fully left. Out the left peak meter in FCP would read -6dBFS, because now in this position the pan is reducing the signal being fed to the left channel by 0dB as opposed to -6dB in the center position. Thus the mono signal started at -6dBFS the pan didn't reduce it any and now the meter reads -6dBFS.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/8/2004 8:08:43 AM

"My goal is to get the SF edited VO clips to match the FCP edited videos without futzing with levels."

Not sure what the problem is here and all the futzing around with the tones anyway. It's really not that diificult, you're making a mountain out of a mole hill.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/8/2004 8:20:11 AM

O.K. I understand what you're saying. Thanks.

Yes. When I pan that sound file in FCP 'hard right' or left. It is -6db on one side of the meter only.

So, in your opinion, what's the 'problem' here? Does FCP not handle a mono file 'correctly' by lowering the volume or does it just handle it 'differently?' Why wouldn't the result in FCP be the same as in SF? Are these just 'common' differences in audio applications or is this unusual? Do I need to call Apple and tell them to 'fix' FCP? lol

I really want to get to the bottom of this so that I know exactly what to do the next time this come up and/or have a simple logical explanation for someone else should they ask.

Once again, thank you!

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/8/2004 8:27:15 AM

Bottom line:

'SF and FCP handle mono sound files differently.'

Can I sum it up to that? I completely understand that there are simple 'fixes.' That wasn't the point of this thread. I wanted to fully understand the issue.

Thank you very much for helping me to clear it up.

Ed

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: Rednroll

Date:12/8/2004 12:05:22 PM

The summary is that they just handle them differently, neither is wrong. FCP is made to mix multiple files together, where you would be concerned with center channel build up problems, thus there's a use for this type of PAN. Sound Forge is not a mixing app and is a wave editor, so does not have as much of a concern for the center channel build up due to mixing multiple tracks. It seems like you already know the level difference, so you would just raise the level +6dB in FCP to make it have the same level as in Sound Forge, assuming the pan is set to the center position. Another solution you should look into is to see if FCP has different PAN mode types. I'm a Vegas user, therefore unfamiliar with FCP and Vegas has multiple PAN types to select from, so you could adjust the PAN type for each audio track so that it mimicks the behaviour in Sound Forge. Vegas has this same type of Pan mode available as FCP, but doesn't default to the "Balance -6dB center" mode like FCP. Vegas actually defaults to a "Add channels (0dB center)" pan mode option, which in my opinion is the better option, because if you really want to reduce the level for things panned center, then you can just pull the fader level back.

Subject:RE: Reference tone (and all audio) always 6db hotter. Why?

Reply by: EdZeke

Date:12/8/2004 12:31:27 PM

Awesome finale! That, I guess, sums it all up. Wow, what a thread. Everything makes sense to me.

Rednroll, thank you so much for your time and information. I am a little smarter now.

Thank you and happy holidays!

Ed

P.S. - I hear you got 10 new 'grandchildren' in a single day. Just wait 'till they grow up!