I read about these little speakers called bone conductors. Bone conductors are like speakers but instead of creating sound waves with a speaker cone, they transmit the sound in vibrations. You can put them against different places on your skull to hear the sound. Nobody else can hear the bone conductor and you can still hear everything else. The best place to put them is on the bone above or behind your ear. Bone conductors also work on your
chin, teeth and skull. The skull doesn't work very well. Be careful putting it in your mouth because it is electronic and you could short circuit it.
The quality of the bone conductor is pretty good but they're
not as good as regular headphones.
I thought of putting them into a pair of sunglasses. I thought about different ways of mounting it and how I could do so discretely. It consists of a pair of sunglasses with a wire necklace that goes under your shirt. The battery hangs from the necklace. The sunglasses didn't hold the bone conductor against the bone very well so I put a rubber band on the end of the sunglasses which fixed that.
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Step 1: Parts and Tools
-A pair of sunglasses. Preferably black to be the most discrete.
-A bone conductor. You can get one of these for $8.95 on AdaFruit here: http://www.adafruit.com/products/1674
-A small amplifier with about 3.7 watts. You can get one of these for $8.95 on AdaFruit: http://www.adafruit.com/products/987
-Some wire. I used black but tan or clear might look better against your skin.
-Two pairs of two pin connectors. I used JST connectors but any small two-pin connectors would work. One pair is for the battery and one is for the audio to the sunglasses. You could make it completely without connectors but it's easier to take on and off and charge with connectors.
-Some duct tape or gaffer's tape. Preferably black.
-Either a 3 "AA" battery holder and 3 "AA" batteries or any amount of 1S LiPo batteries and a 3.7V to 5V voltage booster. I recommend using LiPo batteries because they are much lighter and you can recharge them. I used 6 LiPos that are a similar shape and size to "AA" batteries which you can get from here: http://www.hobbyking.com/hobbyking/store/__39491__Turnigy_nano_tech_1200mah_1S_15C_Round_Cell_US_Warehouse_.html I got the voltage booster here: http://www.hobbyking.com/hobbyking/store/__37813__TURNIGY_Voltage_Booster_for_Servo_Rx_1S_to_5v_1A_USA_Warehouse_.html HobbyKing is a great site, they have good deals on all kinds of hobby parts.
-An on-off switch. You don't need one if you get a "AA" battery holder with a built in switch.
-A small nail and a washer
-A rubber band
-A small piece of foam about 0.6" x 0.8" x 0.3". This can be used in-between the sunglasses and the bone conductor. It's not required but it may stop the speaker from vibrating the sunglasses causing other people to hear it. It also might make the bone conductor fit more flush against your bone.
-Hot glue gun
You also need to know how to solder and some basic electronics knowledge.
Step 2: Modifying the Sunglasses
Strip the wires of the bone conductor and a male 2-pin connector. Optionally put some black heat shrink or tape over both entire red wires to hide them. Use a lighter to shrink the heat shrink. Put a small piece a little longer than the length of wire you stripped off on both wires. Solder the two wires from the connector onto the wires of the bone conductor making sure to match the positives and negatives correctly.
Get the gaffer's tape ready. Put on the sunglasses. Put the bone conductor in-between the bone above your ear and the sunglasses, the side of the bone conductor with the screws and small bump should be facing your head. Move the bone conductor around to find the best place that it fits. Hold it in place and take off the sunglasses. Tape the bone conductor onto the sunglasses.
You can put tape around the sides of the bone conductor to make it more hidden. Tape the wires to the sunglasses. Cut the rubber band and glue one end of it to the end of the sunglasses.
Get the nail and washer. Glue the washer to the end of the nail. Glue the nail to the other side of the sunglasses sticking out about half a centimeter.
Step 3: Make the Battery Pack
If you are using LiPos:
Put two sets of three LiPos (any amount will work, I just used 6) together and tape them together with gaffer's tape. Make sure that they are held together tight. Take a few small pieces of wire that are long enough to connect the soldering tabs on the batteries together. Solder all of the tabs on the positive end together and do the same with the negative end. Cut three pieces of wire that are about half the length of the batteries. Get the switch ready. Unsolder the pins on the voltage regulator keeping track of positive and negative on the board and solder the wires from the battery onto the positive and negative on the board where you unsoldered the pins.
Cut the wire on the regulator that has a connector and solder on one of the female 2-pin connectors. Solder the negative pad on the other side of the regulator to the negative on one of the batteries. Solder a wire to the positive pad on the regulator and the other end to one pin on the switch. Solder another wire to the other pin on the switch and the positive on one of the batteries. Some switches have three pins, you might need to use a multimeter to test which two pins to use. Glue the regulator onto the batteries. Now, glue the switch down, make sure to put it on the edge so it's easy to switch.
Measure out a piece of wire that can wrap around the batteries with an extra 3 or 4 inches. Wrap it around the batteries with one short end and one long end, tie the short end onto the long end so that the batteries are balanced. Put glue over the knot to make sure it stays. Tape the wire to the batteries.
If you are using "AA" batteries:
Get a female 2-pin connector and get some heat shrink ready on the wires. Solder the negative from the battery holder to the connector's negative. If the battery pack doesn't have a switch, solder one in between the connector's positive and the battery pack's positive. If it does have a switch, just solder the two positives together.
Step 4: Create the Wire Necklace
Cut two wires that are half the length to fit over your head plus 4 or 5 inches (about 11 cm). Cut three more wires that are half the length to fit over your head plus 4 or 5 inches (about 11 cm) plus the length to wherever your audio source (phone/mp3 player) is. Align all the ends of the wires together. Tape the wires together about two inches from the ends. Put pieces of tape around each wire at both ends and mark them differently so you can tell which wire is which.
Cut another two wires that are about 8 or 9 inches long (about 22 cm). Align them with the other wires so the ends are about an inch further from the other wires. Refer to the illustration. Tape these to the other wires. Put pieces of tape around each wire at both ends and mark them differently.
Split the longer wires into two groups forming a circle and tape the wires. Tape the groups of wires together like you did at the other end. Put a male 2-pin connector on the shorter two of the long wires. Solder the other three long wires onto the 3.5mm audio plug (make sure to put the unscrewed part over the wires before soldering), mark the tape with something indicating which pin on the plug it's connected to. Twist the rest of the wire.
Solder a female 2-pin connector onto the two wires on the other side of the necklace. Screw the other end of the wires from the 2-pin connector to the L-Out on the amplifier. Solder the wire from the left channel (the tip) of the plug to the L+ on the amplifier, do the same with the right channel (R+) to the ring on the 3.5mm plug. Solder the ground from the plug (the sleeve) to another two very short wires that go to the L- and R- on the amplifier.
Solder the ground on the amplifier (GND) to the wire that goes to the negative on the 2-pin plug on the other side of the necklace. Do the same with positive (VDD).
Step 5: Wearing It
To put it on, you put the necklace over your head so that the amplifier is behind your neck and the necklace goes on your chest. Tie the extra wire on the battery pack around the bottom of the necklace so it hangs there. Plug the battery in.
Put on the sunglasses and plug them in to the amp. If you put a rubber band on there, stretch it so that it holds the speaker against your head and wrap the rubber band around the nail on the other side of the sunglasses. Run the wire with the 3.5mm connector down your shirt to your pocket and plug it into your phone or other audio source. Switch the battery on and start playing something or call someone.