How Do AirPods and Bluetooth Earbuds Connect? Pairing, Codecs, and Why They Cut Out

You open the case, an earbud graphic pops up on your phone, and the moment they are in your ears, the music picks up where it left off. Sound crossing the air with no wires has become so ordinary that we never stop to wonder what happens in between. In this post, we will unpack the words you run into as a Bluetooth earbud owner — pairing, codecs, multipoint — and explain why the audio stutters so badly on the subway. No code involved.

Pairing: a one-time introduction and key exchange #

Pairing is the procedure you only go through the first time you connect new earbuds. When you open the case, the earbuds broadcast an “I’m here” signal to their surroundings, and your phone picks it up and shows it on screen. The moment you tap connect, the two devices verify each other’s unique addresses and create a secret key that only the two of them share. It is like two people meeting for the first time, introducing themselves, and exchanging contact information.

The crucial part is that both sides store this key. From the second time on, there is no introduction — the moment the case opens, the two devices simply check that their keys match and connect instantly. The “My Devices” list in your Bluetooth settings is exactly that: a key cabinet.

The key is both an entry pass and an encryption tool. Radio waves are a broadcast spreading through the air — anyone determined enough can receive them — but because the two devices lock the contents with their shared key before sending, the person next to you can intercept the signal and still make nothing of it. This is also why the folk remedy “forget the device and pair again” fixes so many flaky connections: it throws away a tangled key and makes a fresh one.

Bluetooth is the same kind of radio wave as Wi-Fi #

Bluetooth lives in the 2.4GHz band — the very same band shared by your home Wi-Fi and your microwave oven. Its transmit power is much weaker, so its range is short, around 10 meters, and in exchange it sips battery.

To survive in such a crowded band, Bluetooth uses a peculiar strategy: instead of staying on one channel, it hops between channels 1,600 times per second. If one channel is noisy, it dodges to another the next instant, so most interference passes by without you ever noticing.

The trouble starts when there is no clean channel left to dodge to. On a rush-hour subway car, hundreds of earbuds, smartwatches, and mobile hotspots are all crammed into the same 2.4GHz band. Every channel Bluetooth hops to is already occupied, and the audio starts breaking up. Your own body is a factor too. The water in the human body absorbs 2.4GHz radio waves quite well, so there is real physics behind the experience of the earbud on the opposite side from your phone pocket cutting out first.

Codecs: the agreement for compressing sound #

The amount of data Bluetooth can carry at once falls short of sending music in its original form. So the phone compresses the sound before sending it, and the earbuds decompress it for playback — and the agreed-upon compression method is the codec. Sender and receiver have to speak the same agreement, so at the moment of connection the two devices automatically pick one codec they both support.

Here is a comparison of the three you will see most often.

Pair AirPods with an iPhone and you get AAC; pair LDAC-capable earbuds with an Android phone and you get LDAC. No matter how impressive the codec list on the earbud box looks, it means nothing if your phone does not support them — in that case, the connection falls back to SBC, the one both sides know.

Why video is fine but games feel laggy #

Compressing, transmitting over radio, and decompressing all take time. The sound from Bluetooth earbuds typically arrives 0.1 to 0.3 seconds late. So why don’t lips and voices drift apart when you watch YouTube?

Because the video app quietly compensates. It delays the video by exactly as much as the audio lags, keeping the two in step. The video already exists in full, so starting it a beat late fools everyone. Games are different: they have to react to your input in real time, so the screen cannot be delayed. The picture shows up on time while the sound runs 0.2 seconds behind — you fire a gun and the bang trails after it, and the mismatch is impossible to ignore. That is why gaming earbuds advertise a dedicated low-latency mode.

Multipoint: connected to two devices at once #

There is a feature where, while you are watching a video on your laptop, an incoming call makes the earbuds switch over to your phone on their own. It is called multipoint, and the principle is simple: the earbuds remember two pairing keys instead of one, keep connections to both devices alive at the same time, and follow whichever one is making sound.

AirPods’ automatic switching works a bit differently. Instead of Bluetooth multipoint, it is Apple’s own feature that hands the connection off between devices signed into the same Apple account. The result looks similar, but this is why it only works among Apple devices.

Three things to check when the sound cuts out #

Finally, let’s fold this post’s knowledge into a one-line diagnostic. When Bluetooth keeps dropping, check in this order: distance, interference, re-pairing. First see whether the phone and earbuds are too far apart or your body is in the way. If it only cuts out in certain places, suspect 2.4GHz congestion. And if it misbehaves everywhere regardless of location, the last card to play is forgetting the device and pairing again — making a brand-new key.

To sum up: pairing is a one-time procedure where two devices exchange and remember each other’s identity and a secret key, and that key is why opening the case is all it takes from then on. Bluetooth rides the same 2.4GHz radio waves as Wi-Fi, so it can stutter in crowded places, and your music crosses the air compressed under an agreement called a codec. The next time you open the case and the music carries on, the key handshake happening behind that instant might look a little different to you.