Trying to Understand How to Use the CNF

[cubdukat]

I'm having trouble trying to use the CNF (Continuous Noise Filter) with my vinyl rips.

Does the noise print have to be completely clear of impulse noise?? Also, how long of a sample do I have to take?

I'm also having problems trying to get it to sound natural. I'll have to attach some examples later, but suffice it to say that for things like brass swells, you can tell when it kicks in and out.

[Craig Maier]

A few tips. Always, remove impulse noise first with the EZ Impulse Filter. Then, use the CNF. Sample on noise (between tracks or at the lead-in groove of the record). Sample noise should be around half a second to 1 second long. Keep the attenuation control low (around 10 or so). Do not try to remove all the noise - will produce artifacts otherwise.

Craig

[cubdukat]

Thanks. I'll try that. Do i need to adjust the attack and release controls, or use smoothing or the artifact suppression setting?

[Craig Maier]

For a good basic setting, use attack of 50 mSec and a release of ~200 mSec. Turn smoothing on. One you get used to normal CNF operation, then you can begin to try artifact suppression mode which will allow attenuation setting much higher than10 to 15. It will allow up to around 50, but it is a bit trickier.

Craig

[cubdukat]

I'm giving it a try on some Schumann. The big problem is that it sounds all right on my home system, but when I play the MP3's back, the low end sounds unnatural. I was toying around with the idea of not using noise reduction at all, but I need to to hide the artifacts left behind from the impulse filtering.

I think what I probably need to do is take a couple days off from work and really dig into DC8

[Craig Maier]

If you are getting artifacts from the EZ impulse filter, your settings are too high there too. Try to keep the scratch at around 40, Crackle at around 50 and the Narrow Crackle at around 70. Instead of trying to remove all impulse noise in one shot, run the filter with lighter settings twice or thrice. Also, make your transfer at 48 or 96 kHz - - - that preserves the quality of the impulse noise so that the filter can better discriminate between the impulse noise and the music. After de-clicking the record, then use the sample rate converter to bring it back down to 44.1 kHz (before using the CNF). Another thing with the CNF - - - increase the fft size for better resolution (4096). Also, try dragging all the blue dots that are below 300 Hz all the way to the bottom of the graph.

Craig

[Craig Maier]

More to consider - - - try using the Auto-Spectrum CNF mode. In that mode, it takes its own noise fingerprint(s) "on-the-fly'. Often that improves the noise reduction capability of the CNF. Also, consider using the EZ Clean Filter which is more automated (adaptive) and it works on impulse noise as well as random noise. That may be a good place to start off and then when you get used to the EZ Clean, then consider the other alternative filter combinations.

Craig

[cubdukat]

Thanks for the excellent advice. The tips on noise reduction worked like a charm.

I'm going to try halving each of the values you suggested for the EZImpulse filter to see if I can do multiple passes with those. Or would I be better off selecting, say, something like the "Gentle Scratch and Crackle" preset and doing multiple passes with that?

[Craig Maier]

You would be best off installing several EZ Impulse filters on the filter line in the Multifilter. That way, you can effectively do multiple passes in one pass as each one will operate independently of the other one. That is how I do it. Also, I use Fast Edit mode. That allows me to go back and highlight an area where stubborn impulses have not been removed. Then, I use agressive settings on the EZ Impulse filter, limiting the time period on which it is applied (a few seconds at a time).

[Marc Hildebrant]

I just tried three Continuous Noise Filters in a row. Each was designed to mimic the ears "threshold of hearing" contour. Seemed to work better than just one filter.

Marc

[Craig Maier]

I have not tried three CNFs in a row, but I recall that Doug (on this forum) used two in a row. He used one for the bass with a high fft count and the other one for the treble end with a low fft count. His goal (as I recall) was to obtain better freq resolution on the bass without sacrificing transient response on the top end. Is that similar to your expreiment?

Craig

[Marc Hildebrant]

Craig,

The idea for the experiment was to see if three filters with modest settings would be better than one with high settings to remove noise.
Seemed to work pretty well.

Marc

[Craig Maier]

Hi Marc,

Did you use different fft sizes on each or did you just use different contours (on the graphic)?

Craig

[Marc Hildebrant]

Craig,

I used the same size 8K for each. The contours were similar for the last two, the first had more "action" on the low end.
Do you think that different size FFT settings would help ?

Marc

[Marc Hildebrant]

Craig,

Remembered the problem with large FFT settings...so...Used 8 K on the first and 2K on the next two. Better responds and now no digital artifacts.

Marc