Ultrasonic Noise Annoyances

Discussion in 'General Electronics Chat' started by jimkeith, Nov 16, 2011.

  1. jimkeith

    Thread Starter Active Member

    Oct 26, 2011
    Old CRT monitors had flyback converters that often times generated loud ultrasonic audio--while it was inaudible, at the end of the day sitting in front of a monitor, my ears were reeling from the effects--loud ringing or tinnitus--really put me on edge--do not know how much hearing damage it caused, but I'm sure it did some--thankfully, with the advent of LCD monitors, those days are gone forever--or are they?

    While there used to be a lot of hype about electromagnetic and gamma radiation levels from CRTs, I never heard anything about ultrasonic audio levels.

    When a boy, I could hear the 15kHZ TV flyback transformer--sometimes annoying.

    I suspect that there are a number of other loud sources of ultrasonic noise that are a potentially serious problem--like ultrasonic rodent repellers or burglar alarms--there used to be a few stores that I think ran them during business hours--while I could not hear them, I could 'feel' them as an oppressive something in my head...

    Are there any ultrasonic noise limitation standards?

    Is there equipment available to measure such? I once ran across a gas leak detector that converted ultrasonic signals to the audio spectrum.

    Any thoughts out there, or similar experiences?

    This might make a good project for some university student...
    SgtWookie likes this.
  2. SgtWookie


    Jul 17, 2007
    Very interesting topic.

    Prompted by your inquiry, I Googled "ultrasonic noise limitation standards" and found this paper from Australia:

    This paper is very interesting, because it is not only fairly recent (2004), but compares ultrasonic limitation standards from multiple countries.

    OSHA's noise 29 CFR 1910.95 addresses airborne ultrasonic noise.
    Link: http://www.osha.gov/dts/osta/otm/noise/health_effects/ultrasonics.html

    You wrote:
    When I was working at a company that made crystals (among other products), they used such a converter to determine whether any components inside a crystal filter were clunking around loose by shaking it under the sound pickup. Might sound like a primitive technique, but it was very effective. An ancient HP 4918A is such a device. I can't recall exactly what model we used, but it was definitely a Hewlett-Packard product.

    In this HP article from 1967, they call them "ultrasonic translators":

    If you Google around, you will likely find some translator kits offered.

    As far as precision measurement of such audio ranges; I don't know what to suggest to you.

    I am a tinnitus sufferer. When I was a youngster, the flyback transformer of our TV's was really annoying - it was quite loud to me. After working on supersonic aircraft for a short period of time, that little problem disappeared, along with a good portion of my high-frequency hearing. :rolleyes:

    Although I've been in mostly quiet environments since the early 80's, I've always had a CRT of some sort going nearby. It never occurred to me that it may be impacting my hearing at this point.
    jimkeith likes this.
  3. lowprofile


    Oct 31, 2011
    I, too, am bothered by the high-frequency noises, and I am also perplexed that so many people do not seem to notice. I can hear the sound of my SMPS phone charger when I plug in my phone, too, and know when it has finished charging because the sound stops.

    Because so many people are unable to hear these sounds, it is treated as a non-issue. I had to work in a shop where the stereo had a high-pitched sound that everyone else was able to ignore, but it gave me headaches. I would not be surprised to find that this attitude is entirely common, but the issue does need to be addressed, and there should be regulations concerning commercial products and their sound output. If it were up to me, I'd suggest that we simply expand the range of "normal human hearing" in normal testing.
    jimkeith likes this.
  4. jimkeith

    Thread Starter Active Member

    Oct 26, 2011
    @SgtWookie, never considered ultrasound in regards to its effect on the ears--of course never had one performed on me.

    How about the harmonics of such ultrasound sources? I would not at all be surprised if the signals were not clean.

    I, myself, use hearing protection even when operating the vacuum cleaner--nasty thing! not many realize this one...
    PackratKing likes this.
  5. PC Pete

    New Member

    Nov 11, 2011
    I suffer from severe bilateral tinnitus, which was an "undocumented feature" of many years of opioid treatment for my busted back.

    However, I'm able to work in audio restoration, by using a combination of excellent equipment (amp, headphones, liquid-cooled computer system) and live spectral editing. Since I do most of my work using native 192kHz/24-bit audio (like high-end DVD Audio), I can view and manipulate frequencies up to about 60kHz, which is great for high-order harmonics. But that's just working around the problem.

    One issue that complicates this type of investigation is the frequency response of most pro audio equipment. There's precious few good-quality microphones made with a cutoff above 22kHz! And depending on the response curve, much of the frequency spectrum above around 12kHz can be significantly diminished and/or distorted, even in the most expensive mikes and pickups! There's a good reason for this, I know, but it does make sampling higher frequencies quite difficult.

    So although it's relatively easy to design audio circuits that will work above the "normal" limits in order to measure such frequencies, getting a clean signal IN to the circuit can be extremely difficult, for pro audio engineers as well as us end users. Not only that, but reproducing and editing those frequencies requires some pretty sophisticated gear.

    One area I'm very interested in is hydrophones. These are specifically made to capture and reproduce sounds at the very lowest and fairly high frequencies. But they tend towards expanding the low-frequency end of the spectrum. (The reason I'm so interested in this is my growing interest in whale vocalisations, which cover from less than subsonic (milliHertz) to some quite supersonic frequencies

    I wonder if any ex-Navy or other ex-military members might have some ideas worth following up, regarding any equipment they've used?

    Great topic, and I'm really interested to see what other folks can add!

    BTW, Jim, thanks for your help and suggestions on the other thread the other day (SCRs). That put me in a great position, and it's now working great. I've tried to PM and email you, but I'm unable to... So thank you very much mate! :)
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    Ironic! I was just thinking about this the other day. wondering if loud noises outside the audible range in the plant environment where I work were effecting my hearing. I figured they could, since those little hairs in your ear I assume would break off regardless of frequency.
    Reading through this posts also makes me wonder if my migraines could be triggered by sounds that I cannot hear.

    prior Navy Submariner here: Submarines have high & low frequency hydrophones for active sonar. they are huge and loud and they never get used. Its nothing like in the movies, tooling around in the ocean going "PING...PING...PING"; we used only passive ranging techniques. they get tested once per year for preventative maintenence, and lots of safety measures are put in place before testing, because they can kill you; especially if you are in the water - due to the shockwaves, like as if dynamite were to go off in the water, it doesn't compress like air. Tree huggers always tried to say that we were causing whales to beach themselves when we cam in and out of port because of our sonar; hilarious we weren't even using it. When the active sonar is employed, it sounds like a random hodgpodge of high and low tones, in bursts.
  7. PC Pete

    New Member

    Nov 11, 2011
    "Verify range-to-target... One ping only!" - You meant Red October didn't PING, it BZZZTTed? Oh noes! :) At least they PINGed loudly, they got that much right!

    The hydrophones (receivers) were exactly what I was thinking of. Great big humungous passive microphones. Now, if we could just pare down the size and weight...

    I know organisations like the Woods Hole Oceanographic Institute (and many others besides) must have access to good-quality wide-range pickups, but I don't have any way of "getting in" to find out where they source their equipment from. I've contacted quite a few places to ask, even read some of the published papers in the hope of finding out who makes their equipment, but... no luck so far.
  8. rogs

    Active Member

    Aug 28, 2009
    Same for me! -- the NSAID drug 'Naproxen' wrecked my hearing at 11a.m. 21st January 1993 . Had been taking it for about a month. Just went 'ping' that day.
    Sounds like 'tuned noise' at about 6KHz in my left ear. Still there.......

    Use of ultrasound to disperse kids in this country (UK) uses devices like this: http://www.compoundsecurity.co.uk/security-equipment/mosquito-device

    Wonder if they are actually dangerous?.....
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
    Yes as receivers they are quite amazing devices (or collectively, a device, as they are used in a "spherical array"). We could hear things miles upon miles away, especially if we were in the right spot in the water, as differences in salinity and temperature create "channels" - like wormholes for sound - we could hear ships/offshore rigs hundreds of miles away. I never looked into making my own hydrophones and I wasn't a sonar tech so I didn't get to the nitty gritty of how they work, so I'm only useful for telling stories; sorry.
  10. PC Pete

    New Member

    Nov 11, 2011
    No need to apologise!

    Robert Heinlein was also in the Navy, and he was "only" useful for telling stories, too.

    I'm in awe that you (like many of the senior members here) have done so many truly amazing things. And I suspect you know far more about sound propagation and physics than I'll ever be able to learn! (That's the problem with being self-taught - there's so much I miss out on because I'm too focused on one particular need. Luckily I'm a "man of leisure" now, so I can learn as much as I want!)

    I was also thinking (WRT jimkeith's original ideas) that seismic sensors might also be useful in detecting non-audible frequencies; but from what I understand, they're mostly tuned to subsonic and milliHertz frequencies. Although it's known that animals do react to sub- and super-sonic seismic vibrations, I can't find much literature about those effects that discusses the high end of the spectrum... And most of the designs I've seen for DIY seismic sensors tend to filter out everything above a couple of kHz.

    Still, it's an interesting question...
  11. jimkeith

    Thread Starter Active Member

    Oct 26, 2011
    My uncle (great guy) was a sonar operator on a destroyer during WW2 in the Pacific--he had some interesting stories about karmakazi pilots etc, but unfortunately he is no longer with us to answer questions.

    On microphones and distortion--frequency roll-off is one thing that can be dealt with, but if the microphone acts as a non-linear device (mixer) at any frequency, sum and difference products are generated--otherwise known as distortion...

    Good microphones are both a science and art--and expensive--I sold a few vintage mics on ebay and was amazed to see what they brought.