*-* This Instructable is in English. Please click here for the Dutch version,
*-* Deze Instructable is in het Engels. Klik hier voor de Nederlandse versie.
Hearing with your teeth. Sounds like science fiction? No it's not! With this DIY 'tooth headphone' you can experience it for yourself. Sound usually enters your ears and travels to the inner ear via a serious detour. But you can skip a couple of steps and hear directly with your 'bones'. Scientists call it 'bone conduction'. Read our blog (only in Dutch) to find out how bone conduction works*. Can't wait to try it yourself? Then start constructing with this Instructable!
* Don't speak Dutch? Don't worry! Here's the short version of our blog: Bone conduction skips the eardrum and the ossicles, making it possible to hear by the conduction of sound through the bones of your skull (or even your theeth). Bone conduction is the reason why your voice sounds so different when recorded (because in real life, you listen to your voice through air AND by bone conduction at the same time). Some hearing aids make use of bone conduction. And dit you know that Beethoven connected his own DIY teeth headphone to his piano to be able to keep on making music?
Step 1: Materials & Tools
- DC motor (1.5 - 3 volts) - maybe you can demolish an old toy
- 3.5 mm audio jack - you can also cut the jack from an old set of earphones (but please don't you dare to take the fancy new headphones of your little brother!)
- 30 cm speaker wire (consisting of 2 wires) - when re-using a jack, leave 30 cm of speaker wire
- A short piece of heat-shrink tubing
- A metal rod (+- 10 mm in diameter and +- 20 cm in length) - it works well with a wooden rod too
- Wire stripper
- Soldering kit
- Drill - with the same diameter as the motor axis (usually 2 mm)
- An old smartphone, laptop, mp4-player ... with your favourite song on it
Step 2: Mount Audio Jack
*-* Skip this step when re-using a wired audio jack *-*
- Unscrew the new audio jack and slide the case over the speaker wire, in order to be able to close the jack in the next step.
- Strip 0.5 cm of insulation from the ends of the speaker wire.
- Solder one cable at the middle pin of the audio jack. Cover it with the piece of heat-shrink tubing in order to prevent the cables from touching each other.
- Solder the other cable at the outer pin.
- Carefully close the audio jack case again.
Step 3: Mount Motor
- Solder the other two cable ends to the pins of the motor.
Step 4: Mount Rod
- Drill a hole in the middle of one end of the rod, making the axis of the motor fit in precisely.
- Slide the rod over the motor axis.
Step 5: Connect Tooth Headphone
- Connect the audio jack to your smartphone (or portable computer, or mp3-player, or …) and let your favourite song play … you don’t hear anything!
Step 6: Hear With Your Teeth
- Now bite on the metal rod with your teeth. You can hear the music!
- The sound improves when closing your ears.
*-* This is an experiment that shows how bone conduction works. If you're planning on using the device to actually listen to music with your brand new smartphone, we suggest you to add an amplifier (see step 8). Connecting a DC motor directly to the phone's audio output, might in some cases damage your phone. As an alternative, you can choose to mount a flyback diode between power and ground. Or you can use a piezo instead of a DC motor.*-*
Step 7: Bucket Radio
Instead of a 'teeth headphone' you can also easily turn this device into a 'bucket radio'. Hold the bottom of a cup (or beaker, or bucket) against the motor axis. The music vibrations are now transferred to the can, amplifying the sound.
Step 8: Amplify Music (extra)
Probably, you heard the music play very softly. You can give it a boost by adding a little amplifier. Amplifiers are sold in electronics store, or you can solder one yourself if you’re into electronics (search for ‘small amplifier kit’ in your favourite search engine).