Denoising a Conversation - Tips

[tubeman]

hey guys, got an urgent, strange request today, and i'm gonna do what i can, but wanted to throw this out there to see y'all think.

basically, someone wants me to denoise a horribly recorded conversation, or raise voices so they become intelligible.

now, does any have suggestions for this? as for plugs, i have the waves diamondbundle — when i get the tape i will try to use the restoration plugs and use eqs to mess with boosting/notching out parts of the spectrum, and crazy compression might bring out the quieter voices.

i heard the tape once...can barely hear one person. there's a ton of crackling from clothing brushing up against the mic, and loud analog hiss from the cassette.

[AlexLakis]

The owner for a studio I used to work at used to do this kind of work...

He used the Waves bundle extensively. He would use X-Noise and EQ to remove excess frequencies that weren't important. Mostly, the frequencies you'll be looking for should be in the upper midrange and highs, around 2-7kHz (where intelligibility of speech is more prominent.) Throw all the "X" stuff you can at it. X-Crackle, X-Noise, etc. If you have access to it, Z-Noise is even better. Don't go too overboard, tho, a little context can help, too much unnaturalness can distract the listener from doing his job.

Use the frequency analyzer and see where voices you don't need are popping out and notch them out. Use dynamics processing (possibly combined with volume automation to smooth it out) to bring up the parts where the quieter voices are.

Try not to make it toooo painful to listen to, tho, cuz some poor guy is gonna have to listen to it 50x times after you're done with it.

[Kiwiburger]

IMO, most denoising programs would turn that into a sick-making gurgly mess. I get much better results simply using eq. Try a steep lowpass above 2K and a steep highpass above 1K. (Basically the telephone vocal trick).

I find the residual background hiss would be less obtrusive than a fiercely gated noise floor jerking in and out. But maybe that's just me.

There are some extremely expensive noise reduction software that might do an excellent job, and it's way out of my price range so I haven't investigated. I think it's called CEDAR from memory ...

Back again ... http://www.cedar-audio.com/products/...ge/camnr4.html a good read anyway.

I've had a little success with the Voxengo plugin - but I was mainly looking at music applications, and decided to run with normal gating and eq options.

[Lukester]

Surprisingly CoolEdit has a pretty good denoiser....
I've done quite a few projects like yours and i've had good results starting with denoise first and then moving on to other processing....
Just find a good spot to analyze the hiss.....

[tubeman]

thanks for the suggestions, i think i'll start messing with combinations of eq and x-noise and try to strip out the extraneous elements. the guy is most concerned with having an unintelligible voice being brought to an audible level. i am worried that if the voice actually isn't "on tape," it won't be possible to boost something that isn't there, but i'll mess with it.

[rufus13]

Above are all good suggestions.

Try the processes in different sequences (attack broadband hiss, then bandlimit, X-processes) until the best compromise is found. Re-drawing with pencil may be the best (and most tedious) way to de-crackle small sections.

Background pumping/gating is one of the most annoying things behind voice, imho. A little noise behind voice, but good intelligibility, with offensive artifact reduction (not generation) is probably a reasonable objective.

I've heard some old 1/4 inch r-r tapes of meetings (early 1960's) recorded on Scotch 111 half-track mono at 3-3/4 ip/s that are so clear that trucks rumbling outside the window are nicely reproduced along with speech, pencil-tapping, cigarette lighter ignition, water-glass pouring and drinking. The trick was a good microphone (EV 636?) and a decent recorder. 111 hiss and band-limiting (slow tape) was no problem.

Agree in advance what the delivery format will be.

Don't promise too much (then over-deliver) and get a deposit for half of the time you expect it to take (longer than you might think!).

Or, http://www.gearslutz.com/board/showt...53#post1084753

Best wishes.

kk.

[DrDeltaM]

If the wanted conversation is that buried in noise, simple plugins won't get it out. You really need specialised algorithms like those on Cedar Cambridge for such heavy tasks.

If the conversation is of such importance, you can send the file to a forensic audio service, where they use such tools.

[JonCraig]

i do this on occasion for local law enforcement agencies.

if this is for a police agency, then the "fidelity" doesn't matter, just intelligibility. do extreme bandpassing & eq, then de-noise that. often, i'll find myself using multiple instances of a denoise plug... denoise, then eq, then denoise, then declick, etc. etc. play around with your "signal flow" until you get the best results. you can download the sony oxford restoration plugs for 15 days--they're pretty remarkable, and it's a really easy demo process (unlike waves... who want a blood sample, semen sample, etc.). if you get a good check from the job, consider buying the plugs... karma and all ;-)

--jon