Hi, Tim and Doug,
In many respects cleaning up music/spoken word for release and forensics
are two completely different career paths. While iZotope RX is good at
both, I much prefer projects where I use it for polishing rather than
trying to dig things out of the noise.
I find it difficult to predict how well I can clean something up until
I've done it, as each noise-program combination is different.
A couple of thoughts:
--The iZotope de-hum has two flavours of filters (a little check box)
one seems to have many more artifacts than the other. Sometimes, I'll
use de-hum to remove the fundamental and a couple of very strong
harmonics, while using spectral cleaning to work on the upper harmonics
in another pass.
--I have found that using the spectrum editor (main screen) to remove
some lines of hum is often more transparent than de-hum. Again, the
fundamental and a few lower harmonics.
--Spectral noise has a split/link button on some of the faders. When
split, it allows adjustment of how it works on tonal and noise
components of the sound. This sometimes helps.
--Ozone is a very useful tool. The parametric EQ is similar to the one
in RX, but there are also differences and I think I like the one in
Ozone better, at least for some things.
--The Dynamic Equalizer in Ozone permits a Burwen Dynamic Noise
Filter-like arrangement that can lower the gain of a frequency band (or
shelf) when it has little energy present. That doesn't help with digging
stuff out of the noise, but sometimes the noise is wider band than most
of the program and that can help with intelligibility.
--Dialog Isolate is an interesting function. I find it often is too
jarring, but I have provided a dialog isolated track and a cleaned track
and suggested to the final mixer they mix to suit (it wasn't in the
budget for me to do that when she could and knew the material better).
--De reverb can sometimes help with intelligibility.
Of course, we see all sorts of different levels of noise affecting
recordings, so each one needs customized attention.
I trimmed this thread, but left Ellis's and Tim's last messages.
Unfortunately, Doug's message got posted under a generic "Digest"
subject, so I'm adding that to this string (immediately below).
On 2018-06-24 2:21 AM, Douglas Pomeroy wrote:
> Broadband is of limited usefulness if you are really concerned about
> iZotope's RX Denoise allows tailoring of the Curve, after a noise
sample has been learned,
> and use of the Curve, with the Threshold and Reduction controls, can
optimize results, but
> even after hours of experimentation, you may find little overall
> And people wonder why this work is so labor intensive!
> I have always found parametric EQ to be a very powerful tool in noise
> (I still use iZotope's Ozone 5), since some forms of noise cannot be
> without a parametric filter.
On 2018-06-24 2:34 AM, Tim Gillett wrote:
> Hi Ellis,
> I feel your point about Denoising and voice intelligibility is
> important. At
> least intelligibility is some sort of objective standard by which we can
> measure our success. The problem I see with the standard Denoiser tool
> (spectral subtraction) is that it cant lift the partially intelligible
> out of the noise. It only appears to.
> On Dan's example, it seems to lift above
> the noise, the louder parts of the voice - but those louder parts were
> already intelligible - while leaving the
> quieter less intelligible voice parts still buried in the noise. To
> intelligibility the tool would need to lift the quiet parts of the voice
> out of the noise, but it cant. I remember reading an
> article from a CEDAR representative explaining this to a Forensics
> conference. The tool can only distinguish between soft sounds and loud
> sounds, and assumes that louder sounds are wanted and softer sounds
> unwanted. At some point we have to decide what to leave in (above the line)
> and what to squash (below the line) but in practice
> the voice is mixed in with the noise like eggs are scrambled, and there is
> no clear line. That explains why in a recording where the voice is barely
> intelligible or unintelligible due to broadband background noise, the tool
> is useless.
> Someone once wrote with some irony that the (spectral subtraction)
> Denoiser tool works best when it's least needed...
> Tim Gillett
> Western Australia
> ----- Original Message ----- From: "Ellis Burman"
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Saturday, June 23, 2018 11:44 AM
> Subject: Re: [ARSCLIST] Processing micro cassette audio using iZotope RX5
> I agree with Tom Gillett. The adaptive mode of the RX denoiser takes quite
> a bit of time to settle in, and can often over or under process the first
> few words of a sentence before it settles. Especially since the noise is
> fairly consistent in your case, you should use the manual mode and "learn"
> the noise between sentences. This will give a more consistent and
> effective result than the adaptive mode.
> The de-hum in RX is terrible. The notch filters ring like mad. I love RX,
> but that is one feature of it that I find unusable. Luckily, we have Cedar
> here, which is crazy expensive, but works like magic, with few artifacts.
> If RX is all you have, I'd be very careful using the de-hum. I'd use it as
> lightly as possible and listen carefully for the ringing filters. If you
> have an FIR EQ with a high enough Q, you might be better off using a few
> bands of that, instead of RX de-hum. Be careful removing tones with the
> spectral editor too. If you select a long, narrow frequency band and
> attenuate it a lot, it will also ring (and pre-ring!) like mad.
> You should be able to look at the waveform and determine if the clipping
> distortion is playback related. If the clipping is perfectly horizontal,
> then it happened on playback, so reducing the volume should help. If the
> distortion is not horizontal and looks more embedded into the waveform,
> then it likely happened during the recording.
> My thoughts on de-noise - The human brain is very adept at hearing through
> noise, so I've found that removing the noise doesn't help with
> intelligibilty, and often artifacts the audio, making intelligibility even
> worse. De-noise is often the most damaging and abused restoration process,
> so I'd use it very judiciously, if at all. It can definitely make a track
> more listenable, but I have yet to hear it make a track more intelligible.
> The human brain is a much more powerful de-noise processor than any
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
Quality tape transfers -- even from hard-to-play tapes.