Recently, when I was publishing some tech update videos, I came through one amazing tech gadget called SGNL. It’s a band, wearing which we can talk through our finger. When I researched about this product, I found that it uses bone conduction technology. If you want to see that product, have a look to this tech update video.
Than I came through similar products that uses bone conduction technology like,
Bone conduction headphones
Bone conduction speakers
Cynaps Bone conduction smart cap
Watching all this, I got so much curious about this technology that I started deep research on this and try to make any sample project using this technology. And in the end, I succeeded doing this and I am sharing you all my research.
What is Bone Conduction Technology?
Wikipedia has a simple and short definition of Bone Conduction Technology which says,
“Bone conduction is the conduction of sound to the inner ear through the bones of the skull. Bone conduction transmission can be used with individuals with normal or impaired hearing.”
Let’s understand this Inner Ear and Outer Ear concept. Normally we hear by the vibrations produced on our Ear drum, which is regarded as Outer Ear. These vibrations are sent Cochlea which then sends signal to our brain. Here Cochlea is regarded as Inner Ear.
Beauty of Inner Ear is that, It can capture vibrations from anywhere in the skull.Skull here acts as a resonating cavity. So if we place a vibrating device on our head or behind the ears or anywhere around our head, we can hear these sounds through our Inner Ear Cochlea.
So using benefits for our skull and inner ear, some many tech products are developed using bone conduction which seems like magic to a laymen of this field.
Sample Project using Bone Conduction Technology
Main aim of this project was that, I want to create vibrations that can be attached around my head. So 2 things come to my mind that can convert electrical signals to vibrations.
I have tried making bone conduction headphones first. And both of them worked fine but piezo were much better than motors. Let’s see how to make your own bone conduction headphones using piezo transducers.
Initially I tried connecting piezo directly to the phone via 3.5 mm audio jack. And the connections were like this.
You can buy 20mm piezo transducers in pack of 5 from here.
With this connection, your bone conduction earphones are ready…… somewhat. You’ll be able to hear through this but the volume will be negligible. You need to be on a silent place to hear a little.So we need an amplifier in between this to amplify the signal. For that, I have used PAM8403 class D amplifier. It is a stereo amplifier but I have used in mono mode rather than stereo. You can buy this amplifier from amazon by clicking here.
After this amplifier, the quality of sound got better. We can actually hear just like our normal earphones.But yeah, the bass was missing in this piezo headphones. But as we are just making a sample project to test bone conduction technology, it’s really good. Volume is so much amplified with this amplifier, that we can hear from a distant through our outer ear also. But put this piezos anywhere touching the skull, close your ears and you’ll be hearing music without ears. Just like MAGIC……….
Connections with amplifier circuit are as shown below.
With this connections, you’ll get the amplified output at piezo transducer. This is the final circuit of bone conduction headphones.Not only headphones, this is the circuit for all the three projects – bone conduction headphones, bone conduction speakers. and bone conduction band.
You can place the piezo on any surface, this little transducers will vibrate that surface and the vibrations will produce sound. This is the concept of bone conduction speakers.
If you place the transducer in the bone of your finger, vibrations from the bone will be transferred at your finger tip and with that vibrations, you will be able to hear the sound. This is the concept of bone conduction smart band and also of SGNL.
This is it about this project, if you still have any doubt, watch out this video tutorial on this project.
explore | learn | share