Bone Conduction Headphones: Do you need them?

 I've wanted bone conduction headphones for a while, but due to my XL-sized noggin (head) I have a very hard time locating one that would properly fit it. 

Basically, bone conduction does not send audio waves through the air, but instead, directly into your bone, either your skull or your mastoid, by using transducers, not speakers. So you need a transducer that uses a LITTLE pressure against your head, so it achieves a proper... transducing environment. Air gap would not help at all. 

And it really does work. Just that the sound is a bit... weaker, and maybe a bit more "hollow", but it's perfectly audible if you get a good "seal" against your skin. 

There are three major designs for these headsets... The headband type, the "military" type, and finally, the freeform type (eyeglasses, baseball cap, etc.) 

Headband Bone Conduction Headset. The tranducers go in
front of the ears, not on the ears. 

The headband type is the most popular. it is supposed to be one-size-fits-all, which means it doesn't fit me. But it does work: you basically put the transducers on the bone just in front of your ears, and you get sound as if you stuff them into your ear canals. The shape may be slightly different, but they all work the same way. Aftershokz is probably best known and innovates the most, but there are many Chinese makers. of these headsets as well, offering them as low as $40-50. 

Military type bone-conduction headset

The military had long known about bone conduction and how they work, so soldiers can keep an ear to radio while listening to the world around them. The military headsets, however, generally use different plugs as they are meant to be used with military or walkie-talkie-type radios and thus not compatible with regular audio sources unless an adapter can be procured. But people who play serious Airsoft, or have special needs such as security, first responder, and so on, who needs the military quality and compatibility as well as environmental awareness of a bone conduction headset. 

Finally, we come to the freeform type, which can basically be any shape at all. Amazon and Bose both have released bone conduction "glasses" with the hardware embedded in the eyeglass "arms".  And there was a Kickstarter earlier. They are not alone. Several Chinese makers have them for sale already. Though the audio quality is at best, questionable (except maybe Bose models). There's also Max Virtual's Cynaps bone conduction baseball caps. What's even better, you can buy DIY kits to fit them to your own caps. 

So if you have a unique application where you need to listen to audio, but also wanted to keep your ears free to hear other stuff, like as bicycling, running in public, delivery, first responder, or otherwise needs situational awareness, a bone conduction headset may be for you.