7 Replies Latest reply: Sep 2, 2014 6:46 AM by SteveG(AudioMasters) RSS

    When during processing is it best to process noise reduction

    Rick0725

      When during processing is it best to process noise reduction?

       

      I am processing a mono music recording from 1977. There a droning noise throughout at about -100db that I need to remove. I have been experimenting with the parameters. 40% NR reduced by 20 % is the ballpark.

       

      This is an outline of the steps that need to be done

      original Mono Audio

      remove 15731 hz 30 db spike

      convert to Stereo

      Apply eq match

      adjust L R center pan and alignment

      correct final volume

      remove 60 hx hum

      noise reduction

      Need a second opinion. please review steps above of what needs to be done, advise best order, and are the NR parameters ok.

       

      this is the sample (the first second or so)

      Dropbox - Untitled 1.wav

        • 1. Re: When during processing is it best to process noise reduction
          C.Salmassy Community Member

          Hey, Rick.

           

          I see where you're going with this. I have a few ideas.  I've worked in Audio Restoration for 20 years, I would would really like you to consider doing ALL of your restoration processing before you start with the remastering and stereo expansion stages of your project.  All filtering, eq, and broadband noise sampling/reduction work much better with the original audio in its mono state.  Also, I have, linked below, a screengrab of the broadband noise reduction settings that work really well with the noisefloor at the head of your sample audio. Also, I would strongly recommend that you processing everything at 32bit for maximum quality and restoration.

           

          I have to ask, that undulating wind-like audio at the beginning is intentional, correct? I was flashing back to Floyd and the mid 70's.

           

          Also, there's a fun little tutorial from Adobe's Jason Levine about using freq. isolation on multiple copies of source audio for stereo positioning and processing.  Also, don't forget the Graphic Phase Shifter / "Mono to Stereo" effect under stereo imaging effects set.  It's a great place to start with some mono expansion...very teakable.  I just used it on a documentary for television on B-roll footage, to widen it out under the Dx/VO tracks.

           

          Dropbox - Mono Track Sample - AuditionCC2014-Screengrab.png

           

          Purple is the filtered audio with Broadband NoiseReduction curve to the right applied

          Green is the original

          Disregard the Blue

          Samples of FFA are from the very last horns phrase at the end of the sample "Dah-Deeee-Dum"

           

          Cheers,

           

          -CS

           

          PS. If you find any of this useful, please LIKE the response below. Thanks

          • 2. Re: When during processing is it best to process noise reduction
            ryclark Community Member

            Certainly all restoration should be done on the original before any other processing. Although you should do some level adjustment before you start to get the overall peaks in the audio up to a good level of about -3db since this will make your hum removal and noise reduction easier to accomplish.

             

            Note that there are also harmonics of the 60Hz hum at 120, 180 and 300Hz which will need removing at the same time as the hum.

             

            The correct noise reduction parameters may depend on what the aural content of the rest of the audio is, which may not be obvious from the few seconds that you have posted here. There is generally no point in removing absolutely all the noise if it is masked by frequencies in the actual audio, as over doing noise reduction can produce extra unwanted artefacts and can also sound unnatural. If large amounts of noise removal are necessary it is best to do it a little at a time, taking new noise profiles as you go, rather than all in one large lump.

            • 3. Re: When during processing is it best to process noise reduction
              C.Salmassy Community Member

              Hi, Rick.

               

              Actually, the statement below,

               

              There is generally no point in removing absolutely all the noise if it is masked by frequencies in the actual audio, as over doing noise reduction can produce extra unwanted artefacts and can also sound unnatural. If large amounts of noise removal are necessary it is best to do it a little at a time, taking new noise profiles as you go, rather than all in one large lump.


              in my experience, I have found what you said to be false with regard to Hum and harmonics, noisefloor, and general EQ issues.  Sporadic, spontaneous anomalies should be fixed during a mono QC / remastering pass, but continuous anomalies throughout should be processed at the very beginning and throughout program.  Spot de-noise is going to end up sounding choppy and inconsistent throughout.  As you may have noticed, my settings were pretty conservative, and yet the playback yielded a much-improved sound.  For the Hum and EQ, I would use an insert plugin to address those issues, that way, you can experiment non-destructively. 

               

              For the broadband de-noise, I would process on a duplicate file of the original and save as such. You can have multiple versions with different processes until you settle on what works best.  I sampled the head of the source file, less than a second, to get a good snapshot. If you haven't already, sample the noisefloor, activate the de-noise plugin, and select the whole file.  Then, check the box for listening to the removed sound only, and that will help a lot with what's being removed... -10 dB is a 166% reduction in noisefloor.  Your 40% reduction at -20 dB is about 133% or an 8 dB overall noise reduction.

               

              It's been my experience with this process in Audition that setting the Noise Reduction slider anywhere from 30 to 90% creates more artifacting that setting it to 100% and using very little level reduction.  Drawing a curve in the freq. box really helps to only process those areas that require it, further reducing the artifacting of the process.

               

              I hope this is helpful in any way. Must best advice would be to experiment with multiple procedures on 3 minutes of program to find the best workflow for the entire project. Once found, replicate with the entire project.

               

              Cheers,

               

              -CS

               

              FYI - what I had to sample sounded like a fade-in, so I had no idea what the actual level of program are

              • 4. Re: When during processing is it best to process noise reduction
                Bob Howes CommunityMVP

                I agree that noise reduction should be pretty much the first things you do with the possible exception of some normalisation.  Generally you're better off working on the noise as near as possible to its original form rather than altering it in any way that makes it less consistent.

                 

                However, one thing I'd say to the OP is that instead of those NR settings he mentions, he should try doing it in several much smaller passes--say 20% and 10dB reduction in each pass.  Between each pass, increase the FFT size and grab a new noise sample.  Working this way you can achieve a greater level of reduction with fewer artefacts.

                 

                I do agree whole heartedly with using "Save As" to keep various stages of the restoration in progress so you can reverse things if you decide to...and keep the original pristine should you want to start again.

                • 5. Re: When during processing is it best to process noise reduction
                  ryclark Community Member

                  Dingler90034 wrote:

                   

                   

                  Actually, the statement below,

                   

                  There is generally no point in removing absolutely all the noise if it is masked by frequencies in the actual audio, as over doing noise reduction can produce extra unwanted artefacts and can also sound unnatural. If large amounts of noise removal are necessary it is best to do it a little at a time, taking new noise profiles as you go, rather than all in one large lump.


                  in my experience, I have found what you said to be false with regard to Hum and harmonics, noisefloor, and general EQ issues.  Sporadic, spontaneous anomalies should be fixed during a mono QC / remastering pass, but continuous anomalies throughout should be processed at the very beginning and throughout program.  Spot de-noise is going to end up sounding choppy and inconsistent throughout.  As you may have noticed, my settings were pretty conservative, and yet the playback yielded a much-improved sound.  For the Hum and EQ, I would use an insert plugin to address those issues, that way, you can experiment non-destructively.

                   

                   

                  I think you may have misunderstood my statement. What I was referring to was Noise Reduction rather than hum, harmonics or intermittent clicks, pops etc. Also when I said "a little at a time" I meant level wise, as re-iterated by Bob, not just small chunks time wise. Although there are times, as I have discovered restoring old optical film soundtracks, when you have to do it in small chunks, shot by shot, as the mix between dialogue, music and effects varies.

                   

                  As you say "Spot de-noise is going to end up sounding choppy and inconsistent throughout" but sometimes it has to be done that way. But then, of course, you have to use various methods that I devised to smooth it out like, surprisingly, adding some consistent carefully selected noise back.

                  • 6. Re: When during processing is it best to process noise reduction
                    Rick0725 Community Member

                    Thanks for your input. Spent the last week experimenting with different processes, plug ins, and settings.

                     

                    original Mono Audio

                    remove 15731 hz 30 db spike

                    convert to Stereo

                    noise reduction

                    eq match

                    touched up eq where needed

                    adjust L R center pan and alignment

                    final volume adjustment

                     

                    I found it better to apply the noise reduction after converting to stereo using this plug in

                     

                     

                    Open Ambience Project "SHEPPi" Free Spatial Enhancer

                    • 7. Re: When during processing is it best to process noise reduction
                      SteveG(AudioMasters) Community Member

                      Rick0725 wrote:

                       

                      I found it better to apply the noise reduction after converting to stereo using this plug in

                        Open Ambience Project "SHEPPi" Free Spatial Enhancer

                      Interesting. I've always found the complete opposite when it comes to SHEPPi, although strictly speaking, it shouldn't make any difference. SHEPPi certainly is the best mono-to-stereo plugin there is, though.