How can humans hear below 20Hz?

How Can Humans Hear Frequencies Below 20Hz?

A common question I'm often asked is: ‘how come it's possible to hear such low frequencies, because humans aren't supposed to be able to hear below 20Hz?'

Similarly…'will I be able to hear the 10Hz tones, as the spec on my headphones/speakers says they only work in the 20-20000Hz range?'

They are both good questions, with a simple answer…

The 20Hz frequency limit regarding human hearing relates to the ‘pitch frequency', which is what the tone/beat ‘sounds like'. This is also what the frequency spec for headphones and speakers is referring to. The lower the note or pitch frequency, the deeper the tones sound. The higher the note/frequency, the more ‘high pitched' the tones sound.

With most of my isochronic tones tracks the ‘pitch frequency' is usually in the 180-200Hz region. Sometimes a little lower, sometimes a bit higher. But it's always well within the range of human hearing.

The Isochronic Tones ‘Beat' Frequencies

Brainwaves are stimulated not by the pitch frequency, but by the frequency of the beat. How often the beat modulates/repeats per second.

If you hear Isochronic tones where it says they have a frequency of 10Hz, this means the beats/tones are modulating/repeating 10 times a second.

So…

  • 10Hz = repeating 10 times a second
  • 5Hz = repeating 5 times a second
  • 7.83Hz = repeating 7.83 times a second

When you listen to the sound of fast, regular, repeating isochronic tones, this will stimulate your brainwaves, and after a while (usually around 6 minutes), the frequency of your brainwaves start to synchronize with the frequency of the beats.

If you listened to an isochronic tones session where the tone/beat repeats 10 times a second, after a while your brain will start responding to this stimulus, and then begin to synchronize its electrical cycles, to the same 10Hz rhythm of the tones/beats frequency.

The Pitch Frequency Doesn't Stimulate Your Brainwaves

The frequency of the pitch, doesn't affect the stimulation of your brainwaves. It just relates to how the isochronic tones sound. I tend to adjust the pitch frequency to the goal of the track.

If I'm creating a relaxation, meditation or sleep related session, I will look at using a lower/deeper pitch frequency, as it's hard to relax to high pitched sounds.

If I'm creating something to make you more alert, focused or increase your energy, I'll consider using a higher pitched frequency.

So although the pitch frequency doesn't directly stimulate your brainwaves, it does play a part in making the sound more pleasant and appropriate for the session in mind.

Why Don't I Quote The Pitch Frequency For Each Track?

As a general rule at the time of writing, I don't usually quote the pitch frequencies for each track up front, just the beat frequency. This is mainly because I think it will just end up confusing a lot of people. For most people, especially those new to brainwave entrainment, all this talk of frequencies can be very confusing.

The key thing you need to know is: ALL of my tracks have a pitch frequency well inside the range of normal human hearing.

If you are concerned about which pitch frequency I've used on a particular track, just shoot me a message and I'll let you know.

6 replies
  1. connie says:

    Hi Jason,

    I love your cognitive enhancement brain entrainment YouTube video. I use it to help meditate relax and Focus! I have not been able to measure the effectiveness but it has helped lower my mental stress (to which I have a lot). I feel it is a bit addicting and that is a positive thing. I have tried purchasing others on itunes -just not the same. I would like to purchase yours for my ipod nano. Is that possible? Please keep doing what you do. To me you are a techno genius!

    Reply
    • Jason Lewis says:

      Hi Connie,

      Thanks for compliment about my Cognition Enhancer product, I’m pleased you are finding it helpful.

      I don’t know much about the iPod Nano, but I believe it doesn’t have internet access, is that right? If not, you’d need to download my music to a device with internet access first, like a laptop or computer etc. Then in iTunes add my music mp3 files to the iTunes library manually, and sync to the iPod Nano. That’s how I do it on my old iPod Classic anyway. I hope that helps. Jason

      Reply
  2. Curtis Rexroth says:

    How do noise cancelling earphones affect the entrainment effect. With my Bose earphones I actually feel a perceptible pressure on my ear drum? My guess is that since it’s the beat not the frequency that entrains the brain waves it wouldn’t affect it much.

    Another question…Do your beat patterns fall into multiples as does the harmonic overtone series and does it fall into the same natural halving pattern? If it does you could amplify a lower beat frequency by layering the harmonic series with the same pitch/beat frequency in the music. I’m sure answers to these questions are in the literature, but I don’t have much time to follow up on my curiosity these days, since the paperwork requirements of Obama-care (with a regulator gun pointed at my head) steal all my time.

    Curt Rexroth DC,MA,CCN

    Reply
    • Jason Lewis says:

      Hi Curtis, the passive noise cancelling headphones shouldn’t be a problem, but active noise cancelling ones can cause a problem with binaural beats, because they are created via the pitch frequency. As you alluded, with my isochronic tones tracks it’s the beat frequency which entrains the brain, so either noise cancelling earphones/headphones should be ok.

      I don’t currently have any harmonic box type tracks.

      Reply
      • Valorie says:

        I had purchased your ADD/ADHD Intense Relief product and had a strange effect that diminished the more times I used it–probably my brain was compensating. Since I listen with Bose active noise cancelling headphones this could be the reason…what is the problem with binaural beats that you mentioned?

        Reply
        • Jason Lewis says:

          Hi Valorie, it is fairly common for people to experience the odd weird sensation at first, especially if they are fairly new to brainwave entrainment, because it takes a little while to get used to the stimulation and the sensations it can create. As you’ve found, once you do get more used to it most of the strange feelings seem to dissipate.

          The active noise cancelling headphones shouldn’t be a problem with isochronic tones, which the ADD/ADHD track uses. Wake Up Without Caffeine is my only binaural beats product. My headphones are just the passive noise cancelling type, so I can’t tell you from first hand experience the exact problem with the active type and binaural beats. But from feedback I’ve read by others in the brainwave entrainment community, they cause a problem with the waveforms created by binaural beats and completely alter the sound to the point that they are not worth using.

          Reply

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