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  • Audio beyond 20_kHz

    Dave Rat posted a new interesting video on YouTube testing human ability to sense 40_kHz tone. Watch the video.



    "Our Nation’s interests are best served by fostering a peaceful global system comprised
    of interdependent networks of trade, finance, information, law, people and governance."
    - from the October 2007 U.S. Naval capstone doctrine
    A Cooperative Strategy for 21st Century Seapower
    (a lofty notion since removed in the March 2015 revision)

  • #2
    If the signal is very strong/loud I believe we can hear/sense it. Unpleasant and gives you like a headache.....reminds me of those cell phone towers or whatever the heck they are.

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    • #3
      Some people can hear 20kHz and above. They're called children and teenagers.

      https://youtu.be/MbYKhEtCRIs

      Whether or not we can hear that high is moot when there's nothing on recordings that high to begin with. Instruments don't go that high, the microphones we record with don't go that high, and the media we record on don't go that high.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        Ultrasonics can give you a headache. Subsonic can too, but the difference is when the subsonic goes away, so does your headache. Ultrasonic it stays.
        We did some "blind" testing in the dorm back in the 70's on his.

        When I was younger, I could hear just above 20K. Going into a TV store was horrible. Many women can hear higher. Being old and suffering from noise in life, I am down into the upper teens according to just the sound coming from tweeters I was doing impedance testing on. Better than most men and better than much of my generation who went to Who concerts stoned.

        My wife still has very good hearing. Tweeter breakup from harmonics cause her great discomfort. So dismissing ultrasonics is not a valid position. A Zobel on the tweeter can be advantageous. I can't hear the difference, but she can.

        FWIW, there is considerable evidence that what we think is a reasonable listening level with earbuds cause permeant damage.

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        • #5
          Originally posted by tvrgeek View Post
          A Zobel on the tweeter can be advantageous.
          I thought a standard Zobel-filter was used to flatten the impedance without affecting the frequency response. What does a Zobel on a tweeter do to the ultra-sonic output?
          My hearing is poo, so I doubt I'd personally notice anything, but I'm still curious for the sake of learning.


          As for the video itself, I'm a little suspicious for a couple reasons. They showed with the microphone how directional the sound was, but many times during the test he wasn't pointing it toward her (mostly on the far-side ear) so she was seemingly pointing out whenever it got close rather than when it was pointing toward her farside/right ear. She also referred to it as a buzzing during the test instead of the piercing highest-pitch needle of sound....so I'm kind of wondering if maybe the device has something of a subtle electric whine or buzz when cranked which would make sense of why she seemed more sensitive about its distance rather than its aim while the high-frequency itself was shown to be very directional and possibly not greatly affected by distance changes.

          Also not sure how much use (for speakers or for danger-sense) the bone-conducting from behind thing would be when it required such a loud sound-source to be detected. Interesting, but probably not super useful.
          My first 2way build

          Comment


          • tvrgeek
            tvrgeek commented
            Editing a comment
            Besides the impedance, it is basically a low Q low pass filter. It does effect the response. That is why we use them.

        • #6
          I remember a bunch of my counterparts in University pulled me across one day to show me how they were able to hear a tone above 20 kHz. They were demonstrating this using a tone generator that they built, a speaker and an oscilloscope to show what frequency was being generated.

          I had a look, then had a good chuckle, turned the oscilloscope's calibration knob back to its correct position, and walked off. They were all embarrassed.

          Occam's Razor, people. Occam's Razor...
          Brian Steele
          www.diysubwoofers.org

          Comment


          • #7
            Originally posted by tvrgeek View Post
            Ultrasonics can give you a headache. Subsonic can too, but the difference is when the subsonic goes away, so does your headache. Ultrasonic it stays.
            We did some "blind" testing in the dorm back in the 70's on his.

            When I was younger, I could hear just above 20K. Going into a TV store was horrible. Many women can hear higher. Being old and suffering from noise in life, I am down into the upper teens according to just the sound coming from tweeters I was doing impedance testing on. Better than most men and better than much of my generation who went to Who concerts stoned.

            My wife still has very good hearing. Tweeter breakup from harmonics cause her great discomfort. So dismissing ultrasonics is not a valid position. A Zobel on the tweeter can be advantageous. I can't hear the difference, but she can.

            FWIW, there is considerable evidence that what we think is a reasonable listening level with earbuds cause permeant damage.
            INFRAsonic is the opposite of Ultrasonic. . . correctly. Personally I always try and drive at supersonic speeds, but my car is only capable of subsonic speeds.

            Click image for larger version  Name:	goldenrod_land_speed_race_car_3.jpg Views:	0 Size:	104.8 KB ID:	1456819
            Last edited by AEIOU; 11-17-2020, 05:19 PM.

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            • #8
              Originally posted by LOUT View Post
              I thought a standard Zobel-filter was used to flatten the impedance without affecting the frequency response. What does a Zobel on a tweeter do to the ultra-sonic output?
              My hearing is poo, so I doubt I'd personally notice anything, but I'm still curious for the sake of learning.
              https://en.wikipedia.org/wiki/Boucherot_cell

              https://en.wikipedia.org/wiki/Zobel_...peaker_drivers

              Comment


              • #9
                I've run thousands of XO sims (I'm afraid that's probably true, maybe sadly in some eyes?) and I've never used a Zobel on a tweeter (nor see any reason to do so). The RC network won't flatten the Z peak @ Fs (AFAICT).

                They're used to flatten the Z- "rise" (typically in the upper half of a driver's range) to enable a more "textbook"-like (low pass) rolloff from standard filters. They typically allow the use of a smaller series coil to roll off the top of a woofer or midrange driver (than if used w/out a Zobel). I don't use them on a 3-way woofer (since they get passed well below the "rise zone") nor do I use them on low Le drivers (since they have very little rise). I guess I MIGHT use them on a tweeter that exhibited a drastically rising top end that needed rolling off - but probably wouldn't since in the upper octaves a larger coil still isn't very large, and wouldn't add much to the cost. (ymmv)

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                • #10
                  I've never used a zobel either. If you must use an off the shelf crossover then they have some benefit, but otherwise they're just a waste of parts.
                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

                  Comment


                  • tvrgeek
                    tvrgeek commented
                    Editing a comment
                    Call it a low Q low pass filter then.
                    If the tweeter is very well behaved, don't need it.
                    If you can't hear worth a darn, don't need it.
                    It is a tool that can be used if you do need it. Personally, I prefer spending the money on a better tweeter, but it is a tool and it does work.

                • #11
                  I might be doing it wrong or maybe I'm just not using it with the right tweeters, but so far it looks like a zobel on a tweeter only drops the >20K response by about 1-3db. Does that follow with what others are seeing or does the zobel usually make a larger difference?

                  I understand that plenty of folks here can probably detect a 1-3db difference enough that it can make a difference in the right situation, but I'd assume you'd normally want a larger drop if you're taming a problem area for distortion or anything else you don't want heard. AKA, if something is making the tweeter distort up there, I'd assume it'd be better to find/fix the problem (if it's something goofy in the signal chain) or add a tiny 2ndOrder LP or notch-filter to more seriously tame down the distortion area.

                  Related question. Is that high-FR spike many tweeters have after their gradual fall-off above 10-15K caused by distortion?...similar to the noticeable FR spike around 3-8K on some aluminum cone woofers?
                  My first 2way build

                  Comment


                  • #12
                    That spike is usually break up mode, just like you can have with woofers and midranges. With woofers and midranges you generally low pass below the break up mode. You could do so with tweeters, if the break up mode takes place within the audible pass band, and if there's any content there to be heard, which takes us back to the original question. None of the sources I listen to extend above 22kHz, and I can't hear anything above 16kHz, so I don't care what the tweeters may or may not be doing up that high.
                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

                    Comment


                    • #13
                      Over a half-Century ago, my hearing was excellent into the 30KHz range. I could pick-out an out-of tune piccolo or A-flat sopranino clarinet by the "beats" with my back turned to the 110 piece symphonic band. War, gunfire and other noise, old-age and strokes have killed my right ear above about 14KHz on a good day, the left will still flirt with 17KHz when I'm not taking blood pressure medicine (yeah, metoprolol and lisinopril play hob with most people's HF hearing, it's in the drug-fact sheet). "Hearing aids" aren't. If you have medium-to-low high frequency loss (say 3Khz to 7 Khz) they may help you understand voices (what they are intended for), but there is no equivalent for hearing like eyeglasses for eyes yet. Enter the graphic equalizer. I can hotten-up my bad frequencies a bit (never more than say +5 dB) and it helps. Strangely, some particular brands/models/designs of tweeters I "hear" better than others, while the graphs show just a 1-2 dB difference at the very most. I'm talking about about three models of Vifas/Tympanites specifically, all excellent squeakers,in well known designs I've copied so go figure.
                      I went to a "pop" singers concert last year and she was using a "pitch box" and after less than 20 minutes I was gone. It was in "The Silver Cow Patty" BOK center which doesn't have acoustics...just louder and louder PA, and I couldn't stand it. The phase shift and delay in that hockey rink/basketball arena is bad to start with. Overdrive the mics and that pitch box was worse than fighting cats at 3 AM.

                      Ricky-Pooh Inc.

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                      • #14
                        I used to feel very uncomfortable all of a sudden when I'd approach the NJ Transit bus station in Atlantic City back when I was picking up and dropping off my wife in transit from NYC. I got near the door and could hear the super-high frequency 'clicker' thingies going off to supposedly keep the young people from hanging on near or in the bus station. Back in my early 30's it really bugged me, though I don't know what frequency they were firing off at. They were LOUD though and it really bugged me at the time though, made me feel irritated or mad, maybe even anxious a bit.

                        Nowadays, some of the cheaper power supplies make a racket in those upper frequencies as well, the one in my kitchen drives me up a wall, I unplug it when it's not being used to power it's Bantam table radio.

                        Not EVERYTHING about getting older is bad I guess.

                        TomZ
                        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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                        • #15
                          Originally posted by tomzarbo View Post
                          I used to feel very uncomfortable all of a sudden when I'd approach the NJ Transit bus station in Atlantic City back when I was picking up and dropping off my wife in transit from NYC. I got near the door and could hear the super-high frequency 'clicker' thingies going off to supposedly keep the young people from hanging on near or in the bus station. Back in my early 30's it really bugged me, though I don't know what frequency they were firing off at. They were LOUD though and it really bugged me at the time though, made me feel irritated or mad, maybe even anxious a bit.

                          Nowadays, some of the cheaper power supplies make a racket in those upper frequencies as well, the one in my kitchen drives me up a wall, I unplug it when it's not being used to power it's Bantam table radio.

                          Not EVERYTHING about getting older is bad I guess.

                          TomZ
                          If it were me, I'd attempt to locate the actual offending part or circuit and either dampen it mechanically-acoustically or add some sort of electrical filtering.

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