15.6kHz interference

Discussion in 'Audio Hardware' started by harry_t, Sep 13, 2016.

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  1. harry_t

    harry_t New Member Thread Starter

    Location:
    Manchester
    Hello all,

    I am studying for a Masters in Acoustics and I am currently researching the presence of a 15625Hz tone (15750Hz in the USA) that I have observed in many mid-90s / early-2000s recordings. It is pretty much undocumented in academic literature but I've noticed that a few people have written about it here.

    I have measured a spike of 16dB or more above the average 1/3 octave-band level (14130Hz to 17780Hz being the band in question). Following a sample of various recordings from the 90s/00s, I found that the interference tone was more prevalent in music recorded or mixed in certain studios.

    The most likely source of this interference is the flyback transformer in CRT screens being picked up by microphones. I believe this is where recordings have been made in a control room where CRTs are present, or using a desk that had a CRT built in. Indeed, sometimes I can hear it fading in or out with vocal takes, probably where a performance has been punched in next to the desk.

    It appears that recordings can also pick up this interference during mixing. To take "The Bends" by Radiohead as an example, the album was recorded in the UK; however, a lot of the album displays the frequency corresponding to the NTSC standard (15750Hz). Sure enough, the album was (re)mixed in the USA.

    For me as a listener, this sound is very off-putting; there are a few albums I am unable to listen to due to it. If nothing else, I feel like the presence of this tone should be paid attention to when carrying out the inevitable next round of remasters.

    I'd like to hear about whether you have encountered this interference, whether as a listener or as an engineer. Any comments would be very welcome!

    Thanks,

    Harry
     
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  2. c-eling

    c-eling They're made of light,We never would have guessed

    Can it be represented by a line I see when I'm doing lp transfers? I come across this often...
    [​IMG]
     
  3. Apesbrain

    Apesbrain Forum Resident

    Location:
    East Coast, USA
    Yes, I've also seen it in spectrograms but not ever noticed it in playback. Some of the more advanced DAW software can zero in on and attenuate it.
     
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  4. BuddhaBob

    BuddhaBob Forum Resident

    Location:
    Erie, PA, USA
    I did notch see that coming.
     
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  5. bmoregnr

    bmoregnr Forum Rezident

    Location:
    1060 W. Addison
  6. deadcoldfish

    deadcoldfish Senior Member

    Location:
    Santa Rosa, CA
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  7. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    Harry, I'd say you're going places.
     
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  8. MrRom92

    MrRom92 Forum Supermodel

    Location:
    Long Island, NY
    Taking Back Sunday - Tell All Your Friends. It's VERY prominent on the album's vocal tracks and can even be heard cutting in/out in the mix with the vocal track, on both CD and 1st pressing LP.


    I've obtained an unmastered early copy of the album dated January 2002 and although the recording is incomplete as of that date, I've been able to notch out the transformer whine with good results, then sequence the album back into something resembling the original release.
     
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  9. The Pinhead

    The Pinhead KING OF BOOM AND SIZZLE IN HELL

    I remember having to stuff cotton in my ears when I went to the theater to watch that movie coz I thought the sound was so annoying. Weird, coz I didn't think I was able to hear above 15K at that age. Could not pinpoint what it was other than a terribly trebley overall sound. I remember I could clearly hear flybacks when I was a kid but not anymore after say 20 something.
     
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  10. rnranimal

    rnranimal Senior Member

    Location:
    Ohio
    I see this all the time, but have only been able to hear it myself on the original Forever Changes CD and only one ear picked it up. Izotope can do a great job at removing that. But unless it's really loud, I don't bother.
     
  11. JBStephens

    JBStephens I don't "like", "share", "tweet", or CARE. In Memoriam

    Location:
    South Mountain, NC
    The flyback in Pink Floyd's The Wall is audible when he turns on the TV right after "Are all these your guitars?" Some CRT's whine worse than others. In 2000 I bought a TV and the flyback whine was so bad that I took it back and got a Sony. But I've never had to notch it out of a recording. Brian Wilson's "Smile" album has a "sheen" to it which I first thought was flyback. But I read that it was recorded with tube mic preamps.
     
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  12. tmtomh

    tmtomh Forum Resident

    Led Zeppelin's Celebration Day live album has it - plus a more audible spike around 12kHz, which some have claimed was a frequency coming from Robert Plant's teleprompter.

    Both frequencies were notched out during mastering, but incompletely - they're still visible all over the waveforms.
     
  13. McLover

    McLover Senior Member

    Getting rid of the CRT monitors at work, made the on air and production studios much quieter and cooler. Yes, they contribute noise and heat in the studio.
     
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  14. VinylRob

    VinylRob Forum Resident

    If you live long enough 15k+ information will be pretty much inconsequential... I suggest just waiting it out. (tongue firmly planted in cheek) :)
     
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  15. JBStephens

    JBStephens I don't "like", "share", "tweet", or CARE. In Memoriam

    Location:
    South Mountain, NC
    When I worked in radio, we just used TURNTABLES. No heat, no noise. :D
     
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  16. McLover

    McLover Senior Member

    Did that too, pre automation, with cart machines and open reel machines. Better that way too.
     
  17. There are four CDs in our collection that have this scratchy-sounding, high-frequency tone that only appears in the right channel; it's most noticable during either the beginning or the end of the songs. Is this the high-frequency interference that we're talking about here? Or is it something else? The CDs in question are CDs of Boston's self-titled debut, Pink Floyd's A Momentary Lapse of Reason, Duran Duran's Decade, and Tom Petty's Full Moon Fever that were all done in the 80's.
     
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