Better Noise Reduction With Science

Most noise-blocking headphones fall into two categories: they use some kind of material to absorb or scatter noise, or they use active cancellation that creates a signal to oppose the noise signal. As you’ve probably noticed, both of these approaches have limitations. Now, Swiss scientists think they have a new method that will work better. In Nature Communications, they describe a noise cancellation system that moves air by using ionization instead of a conventional transducer.

With the cool name plasmaacoustic metalayers, the technique uses a controlled corona discharge to create very thin layers of plasma between a metal grid and thin wires. With no voltage, sound passes freely. Applying a voltage across the assembly produces ions and moves air with very low inertia, unlike a typical speaker. By controlling the reverse pressure of air, the system can cancel incoming noise picked up by a microphone.

Ultimately, this turns out to be like active noise cancellation with a better transducer than the typical speaker. While it isn’t exactly the same, it did remind us somewhat of how electrostatic headphones work.

Will we see better headphones from this work? Too early to tell. But it is an interesting way to create a speaker-like transducer, and it may even have uses other than noise cancellation. If you build anything using this technique, be sure to let us know about it.

Amazon wants to make your noise canceling keyword sensitive. But you can always go cheap and just block outside noise as best you can.

18 thoughts on “Better Noise Reduction With Science

  1. You had me at “plasmaacoustic metalayers”.

    I a, sure I will use this regardless of whether it is better or not, just so I can say “plasmaacoustic metalayers”

    1. Headphones with these would be: plasmaacoustic metalayer players.
      If the noise reduction is tailored to the human ear, they become:

      plasmapsychoacoustic metalayerplayers.

  2. Corona transducer marketers make a big deal out of having a nearly massless driver, implying that it’s a tremendous advantage. In practice, conventional speakers have a cone mass about the same as the air that loads the cone, and that air mass is the same as the air mass coupled by a corona transducer of the same size. At best, this gives the corona driver a 2:1 advantage. Unless I’m missing something, added complexity outweighs possible gains.

  3. They’re missing their market – audiophiles are generally gullible enough to shell out the GDP of a small country to have the latest thing and chase zeros in performance. “Plasmaacoustic metalayer” speakers will add at least three zeros to the left of the decimal point. Four if they’re from Apple.

    1. Meanwhile, all popular music has been dynamically compressed to shit since the late ’90s, so there’s an ever-shrinking library of stuff to listen to. I would say a static library, but the record companies are furiously destroying their back catalogs with “remastering.”

      1. How about synthesizer music and chip tunes? Sound chips had a sample rate above 48 KHz, with good channel separation and SNR. Or, let’s think of MIDI files. A soft-synth is merely limited by the sound card (and a big sound fonth). Even an old Asus Xonar D1 will do sound impressive. A DAC with at least 112 dB SNR is goid enough, I think. Or, how about a Roland MT-32? It has a fine audio fidelity. Old DOS games sound awesome via LA synthesis and headphone.

    1. Churches used them? In many games, the portal to other worlds is always portrayed as a plasma. Plasma is dangerous! Before you know it, you’ll be letting a stream of demons into your church!

      Ah well, probably the house of God is the best place to have such a portal, I expect that demons cannot enter a church. Unless it has been desecrated, of course.


  4. It’s still canceling sound so it fails when it can’t be as loud as the noise. I’ve heard noise canceling headphones that have wimpy single 1.5v cell processing amps. They can’t cancel hip hop bass blasting from the street. As shown for walls it’d be great if it would cancel bass bombers inside the house.

    1. It’s not “cancelling” sound, it is “absorbing” sound instead. Put in different words, it does not need to deliver the exact same sound pressure in opposite phase as would a noise cancelling headphone do, but rather accompany the air particles movement (put in motion by the incident sound wave) sufficiently such that it does not bounce on it.
      I like to take the example of the soccer player “chesting” the ball: you just need to accompany the movement of the ball (with same speed,) to keep the ball stick to you. Sound absorption works the same, the air particles are the ball, and they oscillate instead of going straight to the device, but physically it makes the air particles follow the movement of the incident wave so that it does not bounce (reflect) on it.
      You may want to see and listen an exhaustive demo I realized some years ago, presenting the concept (with loudspeakers instead) in use for room modes damping:

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