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How does my audio sound?

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stan welks
How does my audio sound?
on Mar 6, 2010 at 11:11:26 pm

I'm curious to hear what you think regarding the quality of my audio, and its levels in the following clip:







I did not apply any filters, adjust volume, or do anything else to it after recording it.
The video was compressed in Final Cut Pro as h.264 and I applied the following audio compression to the file:

Linear PCM
Stereo
48 KHz
32 bits
Little Endian
quality=best

I used a Macpro, Final Cut Pro, a Mackie mixer, and a Countryman headset.


Thanks for any feedback!



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Jordan Wolf
Re: How does my audio sound?
on Mar 8, 2010 at 1:15:56 am

Stan,

The overall level sounded fine to me and nothing really jumped out. You may want to use some light compression just to even it out some more. Try a ratio of 3:1 and set the threshold so that there's around 3dB-4dB of gain reduction, and, even then, only occasionally. The attack time should be fairly short and the release time should be somewhere in the middle of its range. Apply around 3dB of makeup gain, and I think that should do it.

I can't listen to the clip at full volume right now, nor with the best speakers, so keep that in mind, also. If it's going on the web, I'd expect it to be squashed pretty bad when uploading to a site for streaming. Either way: go for the highest quality you can.

Wolf
<><


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stan welks
Re: How does my audio sound?
on Mar 8, 2010 at 2:13:46 am

Hi Jordan,

Thanks for your response. I am pretty new to all this so I'm going to ask a few follow-up questions if you do not mind:

1.) How does the light compression even it out some more? What does that actually mean? I compress audio from within Final Cut Pro to get it ready for web delivery and decrease file size, though I am guessing you mean something different.

2.) Can I apply what you are suggesting in Final Cut Pro or is this something I need another program for?

Thanks!



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Jordan Wolf
Re: How does my audio sound?
on Mar 8, 2010 at 6:16:16 am

Hi Stan,

To answer your first question, you first must understand the concept of "dynamic range". Dynamic Range is the difference between the loudest sound and the softest sound in a selection of audio. It is usually measured as Sound Pressure Level(SPL) as given in decibels (dB). For example: the human voice has a very large Dynamic Range (let's estimate 120dB).

When you apply compression to audio, you are taking the original, very wide dynamic range (110dB) and lessening it so that the dynamic range is not as large (55dB). This allows the loud parts to be tamed and kept in proportion to the softer parts. The settings I recommended to you will be gentle enough to only affect the audio when it gets a bit too loud.

Using the numbers from before: a 110dB dynamic will be compressed to a 55dB dynamic range if a ratio of 2:1 is used. That is, for every 2dB of input, the compressor only outputs 1dB, effectively cutting in half the dynamic range. To be realistic, let's say that most people talk at around 70dB.

Now then, on to the next part: if that individual has a dynamic range of 110dB, then they have the potential to sound 16 times louder if they shout than if they talk "normally" at 70dB (110dB("shouting)-70dB(normal talking)=40dB). The reason that it sounds so much louder is because, to the human ear, a gain of 10dB is considered twice as loud. So, for every 10dB increase, you double the "loudness" of the sound. I hope that all makes sense. If you have any other questions or are confused, let us know.

As to your second question: yes, it is very possible to use FCP to apply compression to your audio. It's been a while since I've used it, but you might check under Audio Filters or a similar menu listing.

Use compression sparingly and always trust your ears - what really matters, after all, is how it sounds. If it sounds good, it is good...end of story.

Hope that helps.

Wolf
<><


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Rob Forsythe
Re: How does my audio sound?
on Mar 8, 2010 at 2:44:10 pm

[stan welks] "Can I apply what you are suggesting in Final Cut Pro or is this something I need another program for?
"


Add the Compressor/Limiter Audio Filter to a clip and click it into the viewer "Filters" window.

As a starting point, adjust the Settings to my "all 2's" formula:

Threshold (db) -20
Ratio 2
Attack Time 20
Release Time 200
Preserve Volume CHECKED (very important!)

Now click the viewer to display the actual audio track and set the Level to "2" or "3."

Now, when you play the track it should be at a "more consistent" level.

You can play with my "all 2's" formula if you want, but its a good starting point for compressing the levels without a lot of compressor "pumping."
The "Threshold" setting will affect the clip the most... as you slide left, it brings more of the low levels UP.
The actual volume adjustment now comes from the "Level" slider on the actual audio track (and you can key-frame that if you want.)




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Mark D'Agostino
Re: How does my audio sound?
on Mar 8, 2010 at 3:00:49 pm

That's great advice Rob. I also use "2s" as the starting point though the sweet spot for a project I've produced for several years that involves lots of interviews in the middle of loud road construction turned out to be
Threshold (db) -20
Ratio 4
Attack Time 5
Release Time 100

So Rob is spot on as long as you follow his advice that it is a "starting point" and no be afraid to tweak a bit. By the way, our senior editor John guided me into those settings. It's nice to have someone who really knows what he's doing just a door down the hall:)

Mark D'Agostino
http://www.synergeticproductions.com


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Rob Neidig
Re: How does my audio sound?
on Mar 8, 2010 at 4:27:51 pm

And just to help clear up any confusion...

There are two types of "compression"

What Jordan and the others are talking about is a long-used term in the audio world and they describe it well.

The other type of compression is the newer computer-oriented term, meaning to reduce the size of the file. The audio-based compression and the computer-based compression do not necessarily have anything to do with one another. They just use the same term, which can be confusing.

Have fun!

Rob


Rob Neidig
R&R Media Productions
Eugene, Oregon


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stan welks
Re: How does my audio sound?
on Mar 9, 2010 at 9:25:40 pm

Thanks everyone!



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