Bone Conduction Skull Radio

There are many ways to take an electrical audio signal and turn it into something you can hear. Moving coil speakers, plasma domes, electrostatic speakers, piezo horns, the list goes on. Last week at the Electromagnetic Field festival in the UK, we encountered another we hadn’t experienced directly before. Bite on a brass rod (sheathed in a drinking straw for hygiene), hear music.

The TOG Skull Radio demo box
The TOG Skull Radio demo box

This was Skull Radio, a bone conduction speaker courtesy of [Tdr], one of our friends from TOG hackerspace in Dublin, and its simplicity hid a rather surprising performance. A small DC motor has its shaft connected to a piece of rod, and a small audio power amplifier drives the motor. Nothing is audible until you bite on the rod, and then you can hear the music. The bones of your skull are conducting it directly to your inner ear, without an airborne sound wave in sight.

The resulting experience is a sonic cathedral from lips of etherial sibilance, a wider soft palate soundstage broadened by a tongue of bass and masticated by a driving treble overlaid with a toothy resonance before spitting out a dynamic oral texture. You’ll go back to your hi-fi after listening to [Tdr]’s Skull Radio, but you’ll know you’ll never equal its unique sound.

(If you are not the kind of audiophile who spends $1000 on a USB cable, the last paragraph means you bite on it, you hear music, and it sounds not quite as bad as you might expect.)

This isn’t the first bone conduction project we’ve featured here, we’ve seen a Bluetooth speaker and at least one set of headphones, but our favorite is probably this covert radio.

21 thoughts on “Bone Conduction Skull Radio

      1. Brass is normally copper and zinc, although alloys with lead in it exist. You should be able to do this trick also with a thick piece of copper wire, which has anti-bacterial properties.

    1. Only if you ingest amounts sufficient to cause anemia because copper displaces iron biologically. Or it’s poorly refined and has a lot of arsenic in it, but typically I think percentages of that mean you’d have the anemia problem from the copper before your hair started falling out.

    1. Who the heck said it was a new invention? Maybe you should read the entire article. They linked literally 3 earlier bone-conduction audio hacks. Last paragraph: “This isn’t the first bone conduction project we’ve featured here, we’ve seen a Bluetooth speaker and at least one set of headphones, but our favorite is probably this covert radio.”

      Not intending to be negative, but you can’t read, yet you still choose to be Debbie Downer.

    1. I still have one. The FM radio was on a “scan and reset” type. The lollipop end was resting on the center of a speaker (inside). When you put the sucker in your mouth, the audio could be “heard” through the “cavities” in the head. My Kyocera Torque XT does NOT have a speaker (per se) in the top of the phone, BUT…a “motor” to vibrate audio TO my ear. Interesting tech. It is good to see the hearing technology be further studied and implimented for those that are in need of this technology. 73 – KC8KVA

  1. Very cool innovation! The simplicity is amazing.
    ==========================================
    Unrelated Side Bar: I’ve heard stories of wire fences, water taps, and people’s filings being resonated by US Navy CW signals to submarines via ELF and VLF transmitters. Noteworthy is Cutler Maine (USA). Also in Illinois (USA) and Exmouth (Western Australia). Heard that similar things happened to Tesla’s neighbors in the Shoreham NY area when he was operating his Wardenclyffe Tower CW Transmitter.

    I think most people who do use some sort of covert radio tend to like the T-Coil method which is essentially a large induction coil around your neck under your clothes and feeds a pill shaped receiver that is inserted into your ear canal like a hidden hearing aide. The microphone would be hidden in your watch with a audio link to your transmitter. But in reality hidden covert radios are dangerous if you are trying to be clandestine. They can be detected by electronic and physical means. Why would you want someone micromanaging you on a earplug anyway? Extremely annoying when your trying to improvise.

    In my book… if you really need to cheat at a test and not get caught… you need to do it THIS way. Foolproof method to not get caught!

    D’oh!!! *face palms* :P (/humor)

  2. Try a hard drive head positioning motor. It should sound full range and linear response. Feeding audio into these makes a bass actuator for lights or mirrors in sound and light setup. When playing with one I noted how it would have been the ultimate transducer for Helen Keller. One of those tiny form factor drives would be small enough to do the covert radio trick in hifi, or two for stereo. Get ’em while they are still around. SSD’s are here.

  3. woah, just tried this and its soo weird!

    a 30 ohm motor is about a 30 ohm speaker and you wont get much power at 12v with an unbalanced amp

    on my setup i needed low-cut… not enough treble
    maybe because i was using a stepper, maybe i should have tried a DC motor but i didnt have any DC motors of the right flavour ;)

    you know what they say, a motor-a-day makes the machine healthy, but tasting too many machine parts makes you sick

  4. I read a book a while ago, dont remember the name but the main character invented some walkee talkees that you placed behind your molar and they would vibrate so you xould talk to each other

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