Removing white noise

how to

I use n 3.3 and Goldwave as an editor, noise filter. I have some tracks with what I call white noise. Sounds sort of like tape hiss used to. I would like to remove it but dont know what frequencies or filters I should set up using Goldwave. My problem is that i cannot isolate the sound as it rises in the middle of low volume segments. Any ideas?

as always…thanks

cliff

:cool:

The noise you are describing probably is white noise and it would have has equal energy at all frequencies. (Pink noise has a similar sound but has equal energy in every octave resulting less high frequency energy).

This means that your filters have to be chosen to pass only the frequencies you want since the noise is present equally at all frequencies. This is complicated because a normal musical tone has a group of frequencies which are harmonically related to the fundimental (2X, 3X, etc.) with space in between them. A chord has even more frequencies. To put a filter on each harmonic manually would be a pain and they would all have to track any frequency shifts in the fundimental frequency of the note(s). This pretty much rules out a standard parametric equalizer for anything except cutting off the portion of the noise above the highest upper harmonic and below the lowest fundimental.

Some software has more complex dynamic filters that can help. I have used a Sound Forge plug-in and I believe Audition has some specialized filters that can be used but when I last used them (several years ago) I found that they can introduce significant artifacts. These are more audible in a mono file than in stereo for some reason but I wouldn’t use them unless I had no other choice. They probably work with a spectral subtraction technique and typically require you to train them on a selection without signal.

there may have been progress since I last looked so you can search for a “hiss” filter. Someone may have more current experience and be better able to help.

Good Luck,
Jim

If you can isolate the noise itself, goldwave will sample that noise and look for it in your recording and remove it. For instance, find a section that has the noise only (a section that is silent except for the white noise), highlight that section and open the noise filter. Give that noise a name in the save area. Now highlight the entire wave and use the noise you saved as the filter. That should remove all the white noise only.

Thanks guys…
It is a difficult thing to do because I cannot isolate the sound. It is in a part of the track where there is a low signal level. If I use that as the sample to remove as Dr suggests, it will take the music with it. I was hoping that white noise existed at certain frequencies and I could just eliminate them. But, as Jimbob alluded to, white noise is everywhere. I might just be stuck with it. It was one of my first projects and I didn’t really know what I was doing…

Lesson learned

cliff
:cool:

Cliff,

I experience this same phenomena when I record my bass players ampeg amp. At first I thought I would be able to find the frequency by sweeping the spectrum with a high Q spike on my EQ software. No luck. I just deal with it.

Mitch

the noise actually came from a noise gate on my guitar fx pedal which i had not set up properly…i have since remedied that and i also learned not to accept mediocrity and think something can be “fixed later”…

oh well…

cliff
:cool:

Cliff,

This is a good argument for leaving a little leading and/or trailing silence in your .wav files. That way you can isolate a ‘noise only’ sample later for removal.

Don (a day late and dollar short) Gaynor ???

PS: I use Cool Edit 96 (Google) and it has a white noise filter.

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Don (a day late and dollar short) Gaynor


maybe not…I have Cool Edit 96. Can you direct me to the white noise filter?

:)

cliff
:cool:

As jimbob said, white noise has equal energy throughout the spectrum, so if you remove it you remove everything. A good old noise gate can remove noise when there should be silence, but if you just use it on quieter sections, you lose the signal too. There’s ways of making the noise less obvious and less objectionable, but at the end of the day cliff, as you say, you’re stuck with it.

Quote (Don Gaynor @ Mar. 04 2006,18:45)
Cliff,

This is a good argument for leaving a little leading and/or trailing silence in your .wav files. That way you can isolate a ‘noise only’ sample later for removal.

Don (a day late and dollar short) Gaynor ???

PS: I use Cool Edit 96 (Google) and it has a white noise filter.

like i mentioned, this noise is on one of my first projects. you’re right, i have since learned to leave the leading/trailing seconds of ‘noise’.

thanx for the responses…

cliff
:cool:

Check out the Diamond Cut filters. Just google on Diamond Cut. They have an interesting set of filters, one of which might work for you.

I don’t know if they have VST’s yet. If they don’t then you’ll have to pre- or post-process the file, but what the heck…

First, that noise let through by the noise gate probably isn’t truly white: it’s probably colored and (hopefully) pushed into higher frequencies.

But since it’s let through by the noise gate (which is why you don’t have a sample at the beginning – though be sure to look at the end too), you could remove it using a noise gate plug on that track. Of course, this will also kill the signal in that spot, and presumably that’s the problem. In which case you can’t blame the noise gate unless it was the SOURCE of the noise, which it probably wasn’t.

Regardless, you can try setting up the same signal path, but with the noise gate removed or else set with the highest prossible threshold, and record the noise that comes through to set the noise filter, and then try filtering your track. (Be sure to save the original.) Try it several times with different amounts of cut. Then use whichever version sounds best. Most likely you will lose a bit of highs, and you get to pick the best compromise.

Yup, it’s best to get the noise out to begin with, but not always possible.

Cheers
Jeff

I know you already did your tracking, but, the best way to avoid white noise is to not introduce it. If you have a noisy component in your signal chain, either replace it, or see if there is a dsp alternative. In your case, if the hardware gate is truly the problem, then just remove it and use the dsp gate it in nTrack.

As far as removing it after the fact, it will completely change the sound. I wouldn’t recommend it.

Thanks …

I will save the original, but I think I will try Jeff’s suggestion. I can recreate the “noise”, and see what filtering it does to the sound of the track.

Thanks again…

cliff
:cool: