Audio Metering

Posted on by Larry

[ This article was first published in the February, 2009, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]

Here is a dialog between Rich Roddman and Woody Woodhall about last month’s article on audio levels. Woody is a professional audio engineer, president of Allied Post, and president of the LA Post-Production User Group.

Rich Roddman writes:

Thanks for another great newsletter. I always learn something new.


I just want to be sure I understood your article on the audio measuring formula you received from Woody Woodhall.


If I have the tone in my Edit to Tape set at -18 and I am recording to a analog deck such as a Beta SP, if I read this right I should set the deck’s VU input levels to -4 for correct calibration?


I have always found setting meters in FCP or Pro Tools out to analog meters confusing. I ALWAYS check playback for distortion or over-modulation. And it seems when ever I try to find a correct ratio I get different answers from the station engineers where I send my spots.


Any clarity in this area would be grateful.

So, I sent Rich’s questions over to Woody Woodhall who wrote back:

Rich – Just curious why you are using -18 as a ref tone. We have found that in the crazy world of audio specs (which seem to have no rhyme or reason) that -20 in the US is the standard. Are you submitting to Europe or is this for the US? I will sheepishly admit that I haven’t looked at a VU meter in years but in times of yore (OK a few years back..) we would calibrate -20 dbfs tone to 0 on the VU meter.


If this is for broadcast my experience is that the “peak” levels delivery specs are either all over the place or non-existent. In Dec I delivered a commercial to Time Warner cable, I asked for their audio specs. They sent me a very nice sheet that had a lot of information regarding the video and a sentence that said “Program Left should be Channel 1 and Program Right should be Channel 2. ” I then called, found a master control operator who told me to “do whatever you usually do.” So much for standards…

Rich writes back:

Thank you for your time in this matter. To answer your question over a year ago we (the post house I work for) switched to send our broadcast and cable spots via DG Fastchannel. To do so you first have to be approved by there engineers for quality control. The video was fine but we were failing for audio. Their engineer told me that their rules are the baseline of the file should playback at -18 db with the peeks being no more that +6 db over that. So I remixed the test spot in Sound Track Pro using the method I learned from one of Larry’s seminars using normalization and limiters. Then in Final Cut I need to drop the timeline -6 db before exporting the file and compressing in Encore. That was the formula that got me approved for DG. Thinking consistency would be a good thing I reset the output of my Final Cut system to -18. The broadcast stations here in the Tampa area still want spots on beta sp and it is more cost effective send an intern that via DG.


I will set my system to -20 since that won’t effect what I do for DG.

Woody concludes:

The crazy thing here is that we are three working, experienced professionals and still here we are scratching our heads! Europe uses -18 as a ref, US -20 as a ref, some gear comes with a default -12 as a ref… and then the frame rates craziness… so much for our technological improvements… All the best,

Larry wraps up: And who says that video engineers should be the only ones confused about standards?


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