Air conduction or bone conduction: the differences
What they share
Both kinds leave the ear canal open. You hear your music and you also hear what is around you, which helps on the street, on a run or on a bike.
Bone conduction
Bone-conduction headphones rest on your cheekbones and send sound as vibration through the bone to the inner ear. The ear stays completely free, but you feel the vibration on your cheek, especially at high volume.
Air conduction
Air-conduction buds have a small speaker beside the ear that sends sound through the air into the ear canal. There is no vibration on the cheek. The TESNA S7 have 17 mm directional drivers that aim the sound at the ear, so the people around you hear less. The TESNA Open2 have an 18 mm driver and a rear-vented chamber that wins back much of the bass.
How each one sounds
With bone conduction the sound reaches the inner ear through vibrations in the bones of the skull, so some of the energy is lost on the way. The result is clear speech but weaker bass, and at high volume some people feel a slight tickle on the cheekbones.
With air conduction, an ordinary driver placed in front of the ear sends the sound through the air, like a very small speaker held very close. For music you can hear the difference: the low and the high notes arrive more completely, with no vibration on your cheek.
The TESNA models in this guide are air conduction: the S7, with 17 mm directional drivers, and the Open2, with 18 mm drivers.
How much leaks out
Any open-ear bud lets a little sound out, because there is no tip to keep it in. At moderate volume, someone next to you in a quiet office may hear a murmur; on the street, at the gym or in the park nobody notices.
Directional drivers cut the leak, because they aim the sound at the ear canal. If you work in a very quiet office or listen in bed next to someone asleep, keep the volume low or choose in-ear buds for those moments.
Water and dust
For sport the IP code matters too. The S7 is rated IP55 and the Open2 IP56: the first digit, 5, means dust protection, and the second shows water resistance, from water jets (5) to powerful jets (6). Both handle sweat and rain, but neither is made for swimming.
After a workout, wipe the buds with a dry cloth and let them dry before you put them in the case, so no moisture reaches the charging contacts.
At the office and at home
Air conduction buds are not only for sport. Because they do not press into the ear, many people wear them for hours at the office or at home, for calls and background music, without the blocked-ear feeling at the end of the day.
The advantage is bigger on long calls: you hear your own voice naturally and do not speak louder than you need to. And you stay aware of what is around you: the door, the children, colleagues calling your name.
For the office, look also at the everyday open-ear buds, such as the slim, discreet EA16, with aluminium arms at 7.4 g a bud.
Which to choose
If you want nothing on your cheek and a fuller sound, choose air conduction. For running in bad weather, the S7 are rated IP55 and last 12 hours per charge, plus 36 from the case. For calls outdoors, the Open2 have three mics on each side that cut wind noise, and an IP56 rating.
Every model is in the shop, under open-ear sport earbuds and open-ear earbuds for the office.