Sound is a vibration and the more you think about that fact the weirder it gets. It means that everything you've ever heard in your life started off as a movement in the physical world. Something hit or scraped or brushed against something else, and that made the air around it wobble. That wobbly air moved as a sound wave — a pattern of alternating low and high air pressure — and bounced off buildings, trees, loved ones, etc., until it careened into your ear and jangled a tiny trio of bones that live in your head. These vibrations were converted to electric impulses, sent to your brain, and hey presto: you heard.
It's complicated as hell, and like the man said in the infomercial: isn't there a better way?
Bone conduction is ex-military tech
Well, there is, sort of, for a loose definition of "better." For the past couple of weeks, I've been trying out a pair of bone conduction headphones, a futuristic-sounding technology that's about a century old. The specific product I've been using is the Trekz Titanium — a $130 wireless pair built by Chinese company Aftershokz. The company started off making bone conduction headphones for the military, but for the past couple of years it's been trying to push them into the mainstream (with mixed success).
Now, instead of faffing around sending vibrations through the air like a damn clown, bone conduction headphones take a more direct route — sending vibrations straight into the top of your jaw and from there to your inner ear and brain. It's a weird and crazy idea that's mostly worse than using regular headphones, but I can't help loving it all the same.
So, the bad first. Bone conduction headphones just don't sound as good as the regular types. There are a number of factors here, but the main one is that sending vibrations through the rigid material of your jaw requires way more energy than just sending them through the air. It's like the physics you learned back in school. In hard structures the molecules are bounded together more tightly, so it takes more energy to move them. In practical terms, this means that when you turn up the volume on a pair of bone conduction headphones, unless you're physically pressing the speakers against your face, the extra force from the speakers just makes the headphones vibrate in place against against your skin.
This. Feels. Strange.
Turn up the volume too much and the headphones will literally vibrate
It's a not a terrible sensation, but it is a little unsettling. The first time it happened to me I was listening to "Universal Traveller" by Air and I jumped in shock. With the volume turned all the way up, the opening percussion vibrated so much it made me think someone was tapping a pen against the side of my head. Not unpleasant, but a little distracting. Other times, though, it genuinely improved the experience, like a paired physical experience. Listening to the fuzzy riffs of "Bees" by Caribou, for example, was fantastic and fun — the earpieces jumping and fizzing in place like some sort of Willy Wonka headphones. I wouldn't say this is a vote in favor of bone conduction, but it certainly makes for a unique listening experience.
And again, you're reminded: sound is a vibration. Interestingly enough, the first ever patent for a bone conduction listening device was registered by sci-fi publisher Hugo Gernsback in 1924. Rather than being worn on the temples, though, the device was "gripped between the teeth" using a pair of adjustable rubber plates. It's not clear how good Gernsback's "Ossophones" were — it doesn't seem the idea ever caught on — but just imagine an alternate universe where we all wandered around listening to Kanye West and Ariana Grande on musical pacifiers.
Anyway, none of this is to say that bone conduction sounds bad. The Trekz Titanium were about as decent as my regular, not-at-all-audiophile-approved $30 earbuds. But they did suffer from a couple of major downsides, namely weak bass and generally quiet volume.
This second point, though, is tied to the main benefit of bone conduction: it keeps your ears free. With nothing plugged into your ear canals, you can hear the rest of the world just like you would normally. Birds tweeting, cars honking, people telling you "Hey buddy, the earphones go in your ears." The whole shebang.
Listen to your music and the world around you
This means your music has to compete with the outside world, but often, this is actually a good thing. Aftershokz makes this a key part of its pitch, billing the Trekz Titanium as a sports product. The headphones are sweat-proof and flexible (try and guess what metal they're made out of), and are sold using promo shots of healthy young adults roaming about outdoors being young and healthy. If you're trekking or cycling, says Aftershokz, you don't have to choose between listening to music and being aware of your surroundings — you can have both.
And you can, you really can! Bone conduction completely lives up to its promise here, and it makes a big difference if you're, say, cycling in the city and have an irrational fear of getting run over by a truck. Even if you're just walking down the street, your experience of just being outside is changed. I don't want to get all technology-is-isolating-us-from-the-world-around-us here, but you've got to admit, headphones are all about that — turning commutes and other mundane spaces of time into private getaways. With bone conduction, though, you get a blend of outside and inside noise, and the result is you're just more aware of what's going on. I'm not saying I prefer it to regular headphones, but it certainly has its charms. Annnnd then there are the downsides, the main one being leakage. Sound leakage. As in, other people can hear what you're listening to.
When you get down to the technical aspects, bone conduction headphones are really no different to regular headphones. Instead of a vibrating membrane that's designed to get plugged into your ear canal, it's been tweaked to be pressed straight against your bone. But it's still a tiny speaker, and without being plugged into the closed environment of your ear canal, noise gets out. Walk down a busy street wearing Aftershokz and no one will be able to hear what you're hearing, but queue up for coffee or squash into a tube carriage and suddenly everyone's got an opinion on whether Shaggy's greatest hit was "Boombastic" or "It Wasn't Me." (It's "Boombastic" and don't @ me.)
Add together all these factors and despite their futuristic, mandible-vibrating promise, bone conduction headphones don't really cut it against the regular cousins, at least not in day-to-day use. For people who have a good reason to keep their ears open while listening to music I can recommend the Aftershokz, which were comfortable, had solid battery life, useable controls and are a regular top pick among specialist sites. For everyone else, though, you're likely better off with headphones of the regular in-through-the-ear-canals type. Either way, sound is still a vibration.