Hollow-sounding

fcpBob · #1 (**permalink**) 09-05-2007, 05:34 PM

Hi everybody, thanks for any help in advance.

I have an audio track of dialogue, but it is very hollow-sounding, he sounds like he's in a gents cubilcle. What is the best way to bring it under control?

I am using FCP (sorry!), I have played around with the filters but it soon becomes aparent that if you know little about audio you won't get very far.

I need pointing in the right direction, any help will be gratefully received thank you.

fcpBob

LJR · #2 (**permalink**) 09-05-2007, 06:29 PM

Do you mean it has a lot of reverb (echo)?

My first suggestion is to re-record the audio again if at all possible.

Removing excess reverb is actually quite tricky. My guess is that you are going to need to use a combination of the Low Shelf, High Shelf, and Parametric Equalizer filters. If you have Soundtrack Pro then you will have much more at your disposal and would probably be better using that.

terryxpress · #3 (**permalink**) 09-06-2007, 01:51 AM

The times when I've come across that are:
1. when the sound was digitalized at less than 16 bits - hollow tin can sydrome
2. and Just in case...just in case. Are you playing/listening on your computer, or playing back through your stand-alone DVD player? And if the latter, is it playing back the sound through a home cinema system? and if so, have you remembered to turn down the volume on the TV. The first time I was making CDs, aa couple of times I played back to find all this hollowey echoey reverb and thought something had gone wrong with the actual burning of the disc. Wasted a couple of discs in the garbage till I realized. The sound to the home cinema was optical cable, and analog to TV and so reaching it a fraction of a second later.

fcpBob · #4 (**permalink**) 09-06-2007, 12:46 PM

Thanks guys for your help, yes lots of reverb.

Re-recording is not an option unfortunatly, I will have to make do. I'm not geared up for Soundtrack Pro yet, so I will take your advice LJR and have a play.

Terry, the tapes have gone, too late to re-digitise, but I will remember that about 16 bit next time, thanks. I'm listening on my computer with earphones, and on the DVD player it sounds just the same.

cheers
fcpBob

fcpBob · #5 (**permalink**) 09-06-2007, 04:06 PM

Ok LJR, I've had a go, it's not easy.

Couple of questions: Is an echo or reverb a high frequency or low frequency, or maybe mid? I'm trying to learn something here

The high and low shelf filters do make a difference, it just needs something more to narrow it some. The parametric didn't seem to make that difference.

If I think visually, like in sound waves with peaks and troughs, is there a way to get your head around this... or am I right off track?

Thanks LJR
fcpBob

LJR · #6 (**permalink**) 09-06-2007, 09:31 PM

Firstly I'm no audio expert (that's the get out clause) but I'll explain it to the best of my (limited) knowledge.

Reverb itself isn't a frequency (so I can't say it's high or low) but there is/are frequencies in your audio that will be causing more of the reverb than others. Here's the tricky bit, you have to try and determine which frequencies you need to...for want of a better expression...dumb down. Here's where the High and Low Shelf filters could be useful.

High and Low Shelf filters are used to increase or decrease a broad range of high or low frequencies. For example, say you have a sound which is a bit muted, you could perhaps try adding a High Shelf filter to add some high frequencies. Similarly if you had some tinny audio you could use a Low Shelf to perhaps bring up the bass a little - of course you could reduce either of those instead if you wanted. What you need to do is try as best as possible to isolate those frequencies which are causing most of the reverb and then reduce them by about, say, 5 dB (good starting point but you'll need to play about a bit).

I mentioned the parametric EQ for two reasons. The first is that I wondered if it would help you isolate which of those frequencies were causing the majority of the reverb and secondly, once you apply a filter like a low or high shelf then you usualy have to tweak the EQ levels a bit to restore a bit of the clarity you may have lost in the audio you want to keep (for voice clarity play around with the 1KHz range).

This is as much art as it is science and I don't profess to understanding it all myself but I hope some of this helps you get closer to where you need to be. Of course the biggest lesson you should learn from all of this is to take as much time to get the audio right on the day as you do the video. It's often more difficult to correct audio problems than it is video ones.

fcpBob · #7 (**permalink**) 09-07-2007, 09:22 AM

Thanks Lloyd, that's very helpful. I look forward to getting SoundTrack Pro.
One last question: What is the "Q" control in the Parametric filter?

Cheers
fcpBob

LJR · #8 (**permalink**) 09-07-2007, 07:39 PM

The 'Q' slider allows you to broaden the frequency range 'around' the frequency you have specified. One thing I should have mentioned to you earlier is about 'sweeping' the parameter to determine which frequency/ies to work with in your parametric or 3 band EQ filter. You may already be doing this but if not it simply involves setting a keyframe at the start of the audio clip and setting your frequency to, say, 1000 and then one at the end and setting it to 20kHZ you will have a sweep in place. Then as you apply filters you can play the clip and carefully listen for where they affect the frequency spectrum best, this allows you set more accurate values in your High or Low Shelf filters at least as starting points. This way it's not all complete random guess work as to which frequencies to work with and what settings to apply. I also recommend wearing headphones during audio work btw.

fcpBob · #9 (**permalink**) 09-07-2007, 09:48 PM

Thanks Lloyd, I have my work cut out, I will let you know how I get on

Cheers
fcpBob