Play-A-Grill: 

User Interface POV

By: Aisen Caro Chacin

-”Hi, I love Bling, Grillz, and Hip Hop.”

This is Paul, he lives and breaths hip hop. His music makes his style, which consists of jewel decorations from pinky to teeth. His bling-bling shines, and with a bright smile he greets with a grill. This removable jewelry is the epitome of hip hop music fashion.  

He found out that his grill can do much more than be a shiny symbol of hip hop status, when he saw the Play-A-Grill. He couldn’t believe that people are able to hear with their teeth, So he wanted to learn more.

-”Are you serious! How is it possible that my grill can become an mp3 player that I can hear through my teeth? This sounds wack! You have to show me what you mean.

The mp3 player is embedded in a material used in dental cosmetics to make teeth whitening trays. This material allows the enclosure to be compact and transparent protecting the electronics from saliva, and protecting the body from the circuit. These devices are custom fit like most grillz. The plastic allows the device to grip firmly to the teeth of the user.

-”So how does it work? What is inside the circuit? Wait! Is it dangerous? I am used to adorning my mouth with platinum, gold, silver and diamonds.”

The circuit has a few parts an mp3 player that controls your music, a usb connector which allows you to upload new music and charge the lithium battery, sometimes referred to as a LiPo cell. It has a tongue controller that allows you to manage the music flow, whether you want to pause/ play, forward or revert to the next song. The circular pieces on the sides of the molar are motors that transduce the frequency of the sound through bone conduction. These are accompanied by an Op Amp that amplify the signal to its optimum volume.

The LiPo cell can be a bit dangerous, and this is why the circuit is completely enclosed and waterproof protecting your mouth from contact with the circuit. It is advised that you take good care of this device, that you don’t drink or eat while wearing it, at least abstain from any hot foods/drinks.

-”So, technically I will only be able to use this sometimes. Can you tell me more about bone conduction? I still don’t understand how this works. I thought you need your ears to listen to music, not your teeth!”

-”Wait you said there is a motor involved. What?”

Bone conduction works by vibrating the bones to the frequency of sound, In this image above you can see the action illustrated. The sound travels through a cable to the transducer, whether this is a motor, piezo buzzer, or conventional speaker. The magnet in a speaker functions in the same way as the motor. It vibrates to the sonic frequencies passed to it and it moves a membrane that pushes air back and forth. In that case sound is travelling through air, which we can pick up with our eardrums. In the case of the motor it vibrates slightly elapsing the oscillations with small on and off sequences. Because the sound doesn’t need to travel through air, it does not need a membrane to push the sound. Instead it vibrates the molars directly, and any surface around it.

-”OK. So the motor is the speaker, but how does the molar translate these vibrations into audible sound? If this vibrates too fast could this be harmful to my teeth?”

-”Let me wear it I want to experience this first hand”

First place the player in your mouth, so that it fits tightly. Press the play button. Can you hear anything?

-”Its very low.”

Ok, so cover your ears, now. Is that better?

-”Yes.”

Great! Now you see that the vibrations are barely perceivable by touch, they are faint and not strong enough to hurt your teeth. This is why we need to add an Op Amp and why a volume control is irrelevant.

The motor translates the electric sound waves into mechanical movements. Your sense of hearing is a mechanoreceptor, which can translate movement as sound, so long as the wave is in the audible frequency of 20 Hz- 20,000 Hz. In the diagram below you can see the sound traveling from the molar to the jaw, and then resonating the areas that are close to the inner ear.  

In the gray circle depicts the whole inner ear system. There are three ossicles, also referred to as the hammer, anvil, and stirrup. These little bones translate the sound coming from the eardrum and vibrate the cochlear fluid. The cochlea is the spiral bone filled with fluid and its vibration is then translated into neural impulses that are translated into what we perceive as sound in the brain.

-”Oh, I think I get it now. It was easy to find the play button, since its the only button in this interface. How do I change the song to the next?”

The tongue control allows you to pause or play the music with one toggle at the same button. “Where are the other buttons?” You may be asking yourself. In order to toggle the switches of forward and previous commands I devised a simple lever switch, By pressing the lever on the right or on the left you can change to the song you want.

 

-”Why not just use three buttons?”

In the diagram below you will find that the tongue is a bit different in strength and consistency than a finger. Because this organ is softer and larger it requires new solutions for controller interactions. The button in the center is easier to press than the button on the sides, this is because your tongue can form a firm point towards the center, but once you directed to a certain direction it loses strength at the tip using a lot  the muscle power to change its direction. The lever allows the tongue to have more surface area to activate, and because of the curve of the lever it requires a lot less strength to press.

-”I never thought about tongue buttons before.”

Tongue interaction and controllers are a large part of this research, This field is relatively scarce as there are not many uses for it today. The largest function for tongue controllers is to assist paraplegics or people with motor disabilities. Can you imagine new uses for the development of this technology? Would you drive your car with your tongue, or dial a phone number?

-”This has been a very interesting experience. I don’t know if I would like to wear this device all the time, but it is definitely a cool idea. My hommies would definitely dig it, especially since you could share music by locking teeth with a girl, or listen to music without headphones. Now I bite my money and my music”

-”This could be used for so much more than grillz. Have you thought of any other applications?”

Yes! Other applications can be applying this technology to braces. Kids and some adults think having to get braces is a lousy experience, but with this technology it can improve their experience, giving them access to music at any time, even at school and no one would ever know.  Another application could be making a more mainstream device that anyone could pop in their mouth this could also aid  some deaf people who have damage to their eardrum. If their nervous auditory system is intact, this would be perfect for them!