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Strange "Chirping" Noises in Needledrops
Engelsstaub
post Jul 29 2012, 00:34
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I was wondering if someone could help me identify these sounds in the quiet passages of these files. It sounds to me like a chirping, or perhaps a squeaking, and is present and noticeable in nearly every quiet passage.

The first sample is from the start of a song that is operatic and quiet. The second sample is the ending of the same song. I've included it, as it is much closer to the peak of the track, to give a sense of how audible these sounds are.

My skill in iZotope RX2 is limited and I can't seem to figure out how to remove the sounds altogether.
Attached File(s)
Attached File  01___Unknown_Title.flac ( 1.89MB ) Number of downloads: 114
Attached File  02___Unknown_Title.flac ( 1.91MB ) Number of downloads: 91
 


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mjb2006
post Jul 29 2012, 06:22
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There's a 'ghost' waveform throughout the file, concentrated in the upper frequencies, and there's broadband noise above ~18 KHz.
The broadband noise indicates dithering w/noise shaping; that's good.
It's the ghost waveform that's the problem. It's visible in both Spectro and Audition:




(This is the last 1 second or so of the 2nd file).

So I suspect the original was downsampled with a very bad resampler. What was in the original that's manifesting as a "ghost" here, I don't know. I'm not an expert in this kind of thing.
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Engelsstaub
post Jul 29 2012, 10:19
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That's interesting. I know little about what I'm looking at when viewing or trying to discern the ghost waveform. The file was recorded with a bit depth of 44.1. I upsampled it to 32/44.1 from VinylStudio's output options so I could tweak it in iZotope RX2 Advanced. The resulting samples were dithered back to 16 bits. I don't believe the sample rate was changed at any time.

The chirping or squeaking noises I hear are audible prior to digitization. I can hear them through headphones simply by playing the record through my home stereo. I've no idea what it could be.

EDIT: I guess I do see this ghost waveform you were talking about...



This post has been edited by Engelsstaub: Jul 29 2012, 10:35


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mzil
post Jul 29 2012, 12:46
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I'd unplug the turntable's AC cord and listen to the problematic section, with headphones, while rotating the platter by finger. If the problem is then gone, then it is most likely a motor noise. Is the turntable direct drive?

If however the squeal persists, then try rotating the platter by finger at half speed. If the pitch of the squeal is cut in half when you do this, then this indicates the noise is recorded in the grooves themselves and anyone playing that particular LP would hear the exact same problem, at least if they used the same part of the groove wall. [Different stylus configurations may touch different parts of the groove wall which haven't been distorted in this way, possibly from a poorly tracking needle in that record's past, not that I'm saying that's likely, but it is possible]

P.S. I find it disconcerting that the background (low frequency) turntable rumble noise escalates greatly at the 20 second mark, in sample one, but I take it that is an artifact from some post processing you have applied.

This post has been edited by mzil: Jul 29 2012, 12:54
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Apesbrain
post Jul 29 2012, 16:45
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Before getting concerned that this is a hardware problem, do you hear the same "chirps" on other LPs? If not, it is something specific to this album or to the circumstances under which you recorded it.

You can remove the offensive sounds but not without also taking out some of the HF content. Try a few things and pick the result you like best. iZotope can roll-off all content above 10k which is something I'd try; drastic, but probably better than hearing the chirps. This will also take away the two oscillator tones in that signal both visible as thin horizontal lines; one at about 14k and the other at 17k. These are likely in the original recording and attributable to something in the studio such as a CRT monitor. (Although, if you use a CRT monitor (or tube TV) close to your recording chain I suppose it could be coming in there.)

iZotope also has a tool to manually select and remove "patterns" which may produce a less destructive result although it will take more time and patience to execute. Be sure to save your work often!
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Engelsstaub
post Jul 29 2012, 22:14
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@mzil: the rumble escalates at about that mark because I was performing a noise reduction in the beginning to try to isolate the offending sounds a bit better. The TT is a belt-driven Pro-Ject Debut III (USB) with a typical wall wart power supply. As the preamp is built into the table, I would not expect to be able to try the manual method you suggest.

What I could do is experiment with a different wall wart (and return it when I'm done for a refund...because I'm a prick like that laugh.gif )

@Apesbrain: I hear the chirps on most other LPs. With a bunch of rock and metal that doesn't have quieter interludes and/or outros, I probably just silenced between songs during processing and now I don't hear them in the digitized CD-R versions.

I wish I could find and isolate the sounds then I could use them as a noise sample. Problem solved. ...but I'm basically an amateur using professional-grade software. (And probably a less than ideal TT.)


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Fandango
post Jul 29 2012, 23:14
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Have you tried speeding the record up (tried 45 rpm)? Does that noise also speed up?

To me it sounds more like a grinding noise and I would guess it's a skating issue. Have you set up your turntable's anti-skating correctly?
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Engelsstaub
post Jul 30 2012, 00:01
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QUOTE (Fandango @ Jul 29 2012, 17:14) *
Have you tried speeding the record up (tried 45 rpm)? Does that noise also speed up?

...Have you set up your turntable's anti-skating correctly?


I'll have to try that out. I'm in the process of moving and the TT is packed right now. The table's anti-skating was factory set and checked by my dealer when it arrived from my ordering it.


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Engelsstaub
post Jul 30 2012, 01:28
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Regarding my last post: I was confusing anti-skating with cartridge downforce adjustment.

In any case I have it correctly set according to the manual's specifications, though for a short time I had it on the loop on the wrong notch. (I used a can of compressed air on something a while back and it blew off.) This isn't the case with this recording.

However I did find one needledrop I did that I'm quite pleased with that doesn't exhibit these noises. In fact the condition of the vinyl was so good that I didn't even treat it hardly at all in post-processing. It *could be* that this was recorded when the anti-skating weight was set to the wrong notch.


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mzil
post Jul 30 2012, 01:57
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QUOTE (Engelsstaub @ Jul 29 2012, 17:14) *
@mzil: the rumble escalates at about that mark because I was performing a noise reduction in the beginning to try to isolate the offending sounds a bit better. The TT is a belt-driven Pro-Ject Debut III (USB) with a typical wall wart power supply. As the preamp is built into the table, I would not expect to be able to try the manual method you suggest.

I was a dealer of their's many years back, way before the whole USB connection/ preamp built in craze. I can tell you back then, many customers were unaware that the motor had to be freed from the plinth and allowed to float in its little, rubber belt hammock-like assembly. This helps decouple its vibration from the plinth and platter. [I had also read that they had trouble with this design over time, as the hammock would sag, but I never experienced this with our showroom unit, not that it got much use.]

Here's another thought. If you play an LP with a poorly centered spindle hole [which can cause wow, but that's not related to your "squeal" noise] this wobble will cause the tonearm to sway horizontally, left to right, every 1.8 second rotation. This will cause the aniti-skating weight string to stroke the small metal post it glides over, much like a violin bow strokes a string. This may unintentionally cause a scrape noise, your squeal noise, that the tonearm is transmitting up to the pickup.

The simple test is to temporarily remove the anti-skate string to see if the squeal goes away.
[edit to add: Also just the tonearm pivot itself, swishing left to right every 1.8 seconds, also could be making the squeak. Test by cueing it off the LP and manually swing it left to right while listening through headphones.]

This post has been edited by mzil: Jul 30 2012, 02:04
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Engelsstaub
post Jul 30 2012, 02:12
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I'm going to try those tests out. It'll take a few days to a week before I have things unpacked and ready to go again, but I'll be back with the results when I do.

The motor comes with two transport screws attached. I actually just put them back in the other day (and secured the tonearm before putting it back in its original packaging.)


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