Above the limits of human hearing

May 31, 2021
 by Paul McGowan

18 comments on “Above the limits of human hearing”

  1. Myself, I'd also add that these inaudible frequencies still have an effect upon us. We all know that sub bass can be felt as vibration on our bodies, even if it is only the movement of air, and the same argument might be posed about the ultra highs, although, I believe, the argument is still up in the air on this.

    1. I too believe that frequencies above hearing affect the music we can hear. A violin, for example, produces a wide range of frequencies that are intertwined with what we can hear. Those intertwined frequencies produce a unique tone for the instrument.

      I ask you to think about a pond of water that is very still. Tossing in a rock about the size of a quarter creates waves (frequency). Now toss in a stone half the size of the original stone and it too produces waves. The two waves interact with each other and produce an altered wave.

      If a recording has captured frequencies above our hearing and if the audio system can play those frequencies back that we can’t hear, perhaps that unfolding of the audio band interacts with what we can hear and helps to provide what was heard at the time of recording?

      We know we can take a pristine source and play it back through a Soundesign (1980’s K-mart receiver) and it’ll sound different than playback through PS Audio’s system.

      I conclude that what we can and cannot hear when audio is reproduced is one part of why recorded music never quite sounds real, although still extremely pleasant.

    2. I am much more worried about all of the RF that has been going through us for all our life times. If you have a pocket transistor radio, whatever it picks up so are you and me.

      My personal feeling is that this is why cancer is so prevalent to day. My wife has had it twice, and now me last fall with prostate cancer. I used to be a broadcast engineer working in the studio and under the antenna tower, so....I think some of us have a predisposition based on genetics.

      My grandfather who came from Italy died of TB in 1938, my father from polio at age 30 in 1955, my mother had Scarlet Fever as a child and had heart problems and never made it to 50. Genetically challenged for sure....I think.

  2. Two thoughts. First if we hear the affects of phase shift above our sine wave limit, then we do 'hear' those frequencies and they matter just in a different way,

    Second we measure frequency response as sine waves but music isn't simple sine waves. It is a combination of many sine waves but integrated into a single wave form at any moment. We don't listen to individual sine waves except in a hearing test. Sine waves are just a useful technical tool to help understand the engineering of our audio gear.

    1. I completely agree that we don't generally listen to individual sine waves. Sine waves are a great tool for measuring and understanding audio systems. I'm not so sure it's helpful to think of a musical waveform as a collection of sinewaves. The complex waveform of a single note on an acoustic musical instrument arises from the physical nature of the soundboard, pipes, strings, hammers, reeds and suchlike, and the associated non-linearities and resonances. Of course, it's possible to decompose the waveform into a set of sine waves using Fourier analysis, but the sound production process does not directly generate multiple sinewaves.

  3. This mite not make any sense to any of you, but I know a little about this subject.
    A def person may not be able to hear the same sounds that we hear, but they do know that they're there.
    Like a dog can hear super high frenclicies, they can hear the super low frenclicies too.
    I don't fully understand this right here, but a def person can hear them too.
    But not very clearly.
    You take a def person in to a church that has a pipe organ, they can really tell that, someone is kicking the heck out of those bass petals.
    Some of those notes, we can't hear them.
    But we sure can feel them.

  4. In my case, I haven't heard a thing above 13,500 Hz since the late 1960s due to a mishap with an IONOVAC system and a botched attempt to use an amplitude-modulated 32 kHz carrier to deliver low-frequency sounds in an attempt to get around standing wave issues. Nonetheless, I use a super tweeter now because I can tell the difference in the clarity of high-frequency sounds such as brushes on cymbals and impact/impulse sounds. Brass instruments sound more complete and, yes, fuller when listening through a system with a super tweeter to music with so-called high res output such as SACD or DSD.

  5. Dear Paul,

    In this video you basically state that the reason electronics are designed with greater bandwidth than 20Hz to 20kHz is so that filtering effects of the design (no piece of equipment has unlimited bandwidth), such as phase shifts (changes in timing between two or more audio signals), do not come down into the audible range of the audio signal and cause distortion that you can hear. You state such a result is not good because it is audible (with music?), so electronics are therefore designed with bandwidth much higher than just 20kHz.

    As stated by Dr. Floyd Toole, “Many investigators over many years have attempted to determine whether phase shift mattered to sound quality (e.g., Greenfield and Hawksford, 1990; Hansen and Madsen, 1974a, 1974b; Lipshitz, et al., 1982; VanKuelen, 1991). In every case, it has been shown that if it is audible it has a subtle effect, most easily heard through headphones or in an anechoic chamber using carefully chosen or contrived signals [not music!]. There is quite general agreement that with music reproduced through speakers in normally reflective rooms [like with the IRS Vs in your listening room], phase shift is substantially or completely inaudible. When it has been audible as a difference, when it is switched in and out, it is not clear that listeners had a preference.”

    Again, with specialized signals listened to through headphones (eliminating room reflections—though even headphones have small ear and cup reflections) listeners are able to detect changes in the audio introduced by phase shift. However, through speakers in a reflective room (all rooms are reflective) playing regular music, phase shifts introduced into the audio signal by electronics or even speaker crossovers are not discernible.

    1. I don’t know if O’Toole is right or not about phase shift, but since hearing him say in a YouTube video that cables don’t burn in and change sound with the process but rather that we adapt to them over time, I take everything he says with caution.

    2. Yes, I know what Toole says and Amir and the others but frankly that has not been my experience. I appreciate all the work these people do but I've not heard a practical application they are responsible for. (ok, end of rant)

      In my work over years of designing audio products there's been a clear correlation between the -3dB point of an input low pass filter (or HP filter) that is clearly audible. Set a simple single pole LP filter on the input of an amplifier to have a -3dB at, say, 30kHz, and much of the upper end life of the music is muted. It's quite audible.

      The fact we can see phase shift extending down into the very audible frequencies is a big clue as to why this sounds the way it does. My conjecture is that phase shift in the audio band is audible when audibly compared to zero phase shift lower frequencies. In other words, I agree that an across the board phase shift is inaudible. But when much of the signal is zero phase and then the phase begins to shift with frequency, that's when it becomes audible.

      Lastly, Toole and others who have made these observations based on years of testing with subjects haven't used what I would consider resolving audio systems. Moreover, they haven't used experienced listeners.

      There's no arguing about what I and other designers hear. We might argue as to why we hear what we hear and that's fine.

      1. Actually, Toole always discloses the listeners skill. He uses trained (skilled) and untrained listeners and compares the results. He shows the difference between skilled and unskilled. And to state that the Harman research does not use "resolving" audio systems is not particularly serious.

        I am sure that Mark Levinson or Revel or even a JBL M2 are pretty good "resolving" pieces.

        Paul, if you state your "correlation", have you tested your hypothesis with skilled and unskilled listeners? Unless you can show proper results, your opinion is just anecdotal.

        1. It is fine to place whatever label you wish on the work. Whatever makes you happy. Fact is, there is a clear and direct correlation between the changes I make in the circuit and what I am hearing. I am not trying to write papers or get my work accepted by AES. That's fine for others. I have products to design and build and a company to run. For those interested in learning more from a hands-on person that actually designs real equipment, then this is a good place to be.

          I've probably written this too many times and it kind of feels like it falls on deaf ears, but let me try again. The fact that a pair of (say) Revels are a revealing speakers or not (they are not. I have owned them), is more than just the choice of speaker. It is also the setup, the electronics that power them: the chain. Going deeper. Imagine a perfect speaker and a perfect chain playing in a bad room or presented in an uncomfortable setting (like a research lab). What value are these results? IMHO about zero.

          Unfortunately, audio is an emotional event and the setting must be correct in order for the person listening to relax enough and not be on guard. It's just not as simple as being in a control group for something like visual acuity.

          Maybe a good way to think of it is like a sex study. Subjects would have to be in the proper "mood" and circumstance to really find out how they act.

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