Super precise, multiband, notch EQ?

[Nippi]

I like to restore and edit music as a hobby.
I'm working on some tracks from the 80s that I've worked on a lot before, and recently I've been testing notch filtering on it to remove a pink line of equipment hum in between the 15000-16000Hz frequencies. Honestly, it's inaudible to my ear, but removing this makes the audio "look" better and it may be something younger listeners could pick up. The hum is a very VERY thin line, and most default notch filters remove too much. I've got it pretty close to where I want it with Audacity's plugin and Fabfilter Q3. I'm wondering if there's an EQ or notch filter out there that has similar results to Q3 but with more precision. I tried messing around with Volcano 3, and still the default notch filters don't remove what I want or remove too much. I haven't quite figured out that plugin but wonder if it's powerful enough to achieve the results I want.

Any tips / advice / plugin suggestions are greatly appreciated. I hope this isn't too much of a newb question since I like to do this as a hobby.

Thanks!

[Benedict]

Odd as I have never seen/heard of this "equipment hum in between the 15000-16000Hz frequencies". I am not saying you are wrong but in 35+ years of this (starting in the REAL 80s) I don't recall this being mentioned.

Is it an mp3 or other transcription thing?
Can we see/hear this?

All you can do is try increasingly expensive devices. I mostly use Q-Range (free) for sculpting. I also have khs Slice (and Carve) which are powerful. Apqualizer is oddly technical so maybe.

But again, I wonder at your initial premise, esp seeing you say you can't hear it. Seeing sound is like seeing a babeful babe, "love" means nothing until you can have a conversation with her.

[Nippi]

Odd as I have never seen/heard of this "equipment hum in between the 15000-16000Hz frequencies". I am not saying you are wrong but in 35+ years of this (starting in the REAL 80s) I don't recall this being mentioned.

Is it an mp3 or other transcription thing?
Can we see/hear this?

All you can do is try increasingly expensive devices. I mostly use Q-Range (free) for sculpting. I also have khs Slice (and Carve) which are powerful. Apqualizer is oddly technical so maybe.

But again, I wonder at your initial premise, esp seeing you say you can't hear it. Seeing sound is like seeing a babeful babe, "love" means nothing until you can have a conversation with her.

Basically, when viewing the song in a spectrogram, there's a pink line going across the audio. Likely from equipment or something the microphones picked up that you really couldn't hear. It's not audible to me, but I'm approaching 30 and your ears change as you age. Someone much younger than me may be able to hear it whereas I can't.

It's a minor thing that can probably be ignored, but if I can notch those signals out precisely without effecting the rest of the audio, then why not?

[Benedict]

With mixed audio - all audio really - there is NO WAY you can do something to one part without affecting other parts. I know the modern mindset decided otherwise but slicing one part of the spectrum affects everything. Just as while me slicing your little toe off might not change you personality in a major way, ie you don't suddenly become Hitler Trump Manson, it affects your balance a bit and that can make you a bit more short-tempered than before.

Taking something away in one part tends to alter the overall balance which can Unmask something else elsewhere. So take great care with what you assume has no impact as it always must.

Again, I don't doubt that you see something but seeing is worth 9/10th of nothing in audio. What if that is a result of a vibration in your personal CD player, or because at some time that was an mp3 (which commonly top out right there)? What if it is simply a rounding error (or bug) in your spectrogram app?

Your image didn't work and we cannot hear pictures of audio so why not post real audio as a Wav file on Google Drive etc. That lets others really be in the conversation.

[Nippi]

With mixed audio - all audio really - there is NO WAY you can do something to one part without affecting other parts. I know the modern mindset decided otherwise but slicing one part of the spectrum affects everything. Just as while me slicing your little toe off might not change you personality in a major way, ie you don't suddenly become Hitler Trump Manson, it affects your balance a bit and that can make you a bit more short-tempered than before.

Taking something away in one part tends to alter the overall balance which can Unmask something else elsewhere. So take great care with what you assume has no impact as it always must.

Again, I don't doubt that you see something but seeing is worth 9/10th of nothing in audio. What if that is a result of a vibration in your personal CD player, or because at some time that was an mp3 (which commonly top out right there)? What if it is simply a rounding error (or bug) in your spectrogram app?

Your image didn't work and we cannot hear pictures of audio so why not post real audio as a Wav file on Google Drive etc. That lets others really be in the conversation.

My bad, I used an incorrect URL. Should work now:



I understand what you are saying, but I was able to get results that didn't look like they had been "spliced" in two. I think a powerful enough plugin and the right settings can achieve what I'm trying to do. I'm just looking for a more powerful, more precise plugin.

An infamous example of this happened very recently, with Taylor Swift's 1989 re-recording. When it was released, her younger fans noticed equipment hum on several of the tracks. After they complained, a new version was uploaded and it appears as though they may have used a technique I'm trying to achieve. I've listened, and could I hear a difference? No. But again - my ears cannot hear those sharper frequencies as clearly anymore whereas younger people still can.

I know it sounds silly to restore music for "looks" but I'm very visual with my approach when doing this stuff. I use other songs as references all the time - so I thought I maybe could try a similar approach on these older 80s Enya tracks I like and see if I could remove that equipment noise.

[Benedict]

That is a spectral plot. Does that show on a Spectrum (EQ type) readout?

Real recordings were covered in equipment noise, no one was paying attention. We were there for the music.

What Enya? I have a few of hers (except Watermark for some odd reason). Again, I would like to hear the very file you have. Is there a reason that you are not sharing? If it was a track others have we could compare our versions to help rule out errors and false flags.

[Nippi]

That is a spectral plot. Does that show on a Spectrum (EQ type) readout?

Real recordings were covered in equipment noise, no one was paying attention. We were there for the music.

What Enya? I have a few of hers (except Watermark for some odd reason). Again, I would like to hear the very file you have. Is there a reason that you are not sharing? If it was a track others have we could compare our versions to help rule out errors and false flags.

Is sharing allowed here? Do you just want a sample? This specific track is from her '86 soundtrack album for BBC's The Celts. It's track 10 (Triad: St. Patrick - Cu Chulainn - Oisin). It's also on the '92 rerelease "The Celts". Several of the tracks on this release have the same equipment noise almost exactly in the same spots.

I noticed her early recordings have that line of possible equipment noise - but this disappeared by her 1995 album after she and her producer and lyricist invested in new studio equipment.

[Benedict]

Like I said share a snippet in a Dropbox etc. There is no real difficulty in that for this situation.
I have that CD so if there does seem to be something, I can compare to the CD (and my mp3 of it).

You keep saying "equipment noise"; what leads you to that conclusion? What equipment??
It is normally low hum or broadband hiss associated with hardware. 15 khz (or whatever that line is) is a very odd, and oddly precise, freq for analog noise.

[imrae]

Spectral editors like Acoustica and RX are meant for this sort of thing. Working in the frequency domain via FFT allows treatment as sharp as possible, as well as alternative processes like smoothing or blurring.

But I would join the warning to be very careful about processing things you can't hear! How will you distinguish "enough" from "too much"?

[Synthman2000]

It is likely Cathode Ray Tube horizontal scan whine, old computer monitors.

https://www.reddit.com/r/audioengineeri ... ?rdt=55717

Either electromagnetic into unbalanced cables or acoustically into mics. Just notch it out as you planned.

Although if you cannot hear it then "default notch filters don't remove what I want or remove too much"

I am not sure how you are judging this ?

Make it 10dB or so lower than anything else up that end of the spectrum and you should be fine Q3 should do the job ok with an extremely tight Q.

Of course there is a trade off with EQ but it is likely a trade off better than a harsh ring for the youngest of ears who will be much more sensitive to it.

PAL/NTSC TV had a 15-16kHz horizontal scan so any TV/old PC monitors could have produced it and given it was BBC they could have had video monitors of various kinds set up. It happened on bedroom/project studios also from people's Atari/Amigas.

[Benedict]

Ok so we have a possible cause.

So when I was singing whilst watching videos kill the radio star on my telly, I was printing some 15-16kHz onto tape.
After I process & mix that, would the line stay as perfect as that? Wouldn't chorus, echo, reverb etc make that messy?
Also if I were not recording, would that whine have become a solid-state on my cassette or mini-disc simply because Asteroids were on in the corner?

I had an Atari (then Boat Anchors with built-in Trinitrons) and I didn't notice. I was a kid once too you know.
So while it may be possible that the CRTs put a stripe in, is that level so low that no one (sane) is ever going to notice (over their own Space invaders machine under fluorescent lights)??

What level is that line representing? Is it above say -45dB?

[Synthman2000]

If you are unlucky these high frequency tones can be greater amplitude than the top end average levels in the track and by quite a lot. They are a potential problem, there is no question about it.

Always have in mind audio may end up on a 20KW sound system, maybe not in is specific case. Guitar pick up may also act as an antenna if this is electromagnetically radiated.

It is reasonably common to find this when remastering audio.

It depends on whether it gets into 1 or multiple source/s (cables/mics/pick ups) as to whether effects processing would impact it, many variables exist.

[CinningBao]

I've this a few times to notch out things like that

https://www.eventideaudio.com/plug-ins/eq65/
Maybe demo it to see if it hits the spot?

[BertKoor]

I've looked at my copy of "The Celts" and can confirm it has the same issue. It's not my habit to look at the spectrum, but it's quite evident.

It's apparent on all tracks except for tracks 9 (Epona), 11 (Portrait out of the blue) and 13 (Bard Dance). I think these were recorded or treated differently. I'd describe it not as hum (that is always a low frequency) but rather as a beep, screech or whine. The amplitude is slightly different on each track, and also varies within the track (due to compression perhaps) so I think it was introduced before mastering.

The frequency is close to, but a bit too low for the typical 16.725 Hz CRT whine of a PAL TV. I'd say it's at 15.6 kHz with an amplitude of -75 dBfs. Maybe the bias circuit of a tape recorder they used was faulty, or there was interference picked up from a nearby CRT.

To make it audible I've slowed down the first few seconds of track 12: Boadicea, twice.
https://www.bertkoor.nl/boadicea_halfspeed.wav

Screenshot 2025-01-29 at 09.00.39.png

My hearing must have deterioated as I can't even hear it at 8kHz. I personally wouldn't touch it, but in Ocenaudio I have applied the BandStop filter set at 15342-16053 Hz (closest it allows) with 20 dB/decade roloff and 3 dB attennuation. When applied twice the line has vanished and it's the same colour as other surrounding tape hiss.

[pekbro]

Maybe have a look at standard eq from sir audio tools, a great and underrated eq.

https://www.siraudiotools.com/StandardEQ.php

This is one of the best eq's available imo, often overlooked these days sadly...

Screenshot 2025-01-28 230533.png