Bluetooth connects headphones, watches, cars, keyboards, sensors and locks. Under the same name, however, live rather different technologies, and the acronyms on the box (versions, profiles, codecs) confuse more than they help. It's worth sorting them out, because audio quality, battery life and compatibility all depend on them.
Two Bluetooths in one
There are in effect two families:
- Bluetooth Classic (also called BR/EDR): designed for continuous data streams, such as headphone audio or a car's hands-free system;
- Bluetooth Low Energy (BLE): designed for short exchanges and minimal power draw, like those of a temperature sensor, a fitness tracker or a tracking tag that runs for months on a coin cell.
Smartphones support both. Many accessories use only one: a BLE sensor won't talk to a device that only knows Classic, and vice versa.
Versions: what they mean
The version number (4.2, 5.0, 5.3 and so on) indicates the features the chip can support: range, Low Energy speed, efficiency, new audio modes. Two practical caveats:
- the connection uses the features both devices share: recent earbuds paired with an old phone work on the phone's terms;
- a high version number doesn't guarantee the manufacturer implemented every optional feature.
So the profiles and codecs actually supported matter more than versions.
Profiles: what a device can do
A profile defines a type of service. The most common:
| Profile | What it's for |
|---|---|
| A2DP | high-quality stereo audio to headphones and speakers |
| HFP | hands-free calls, microphone included |
| AVRCP | playback controls: play, pause, next track |
| HID | keyboards, mice, controllers |
| GATT | foundation of Bluetooth Low Energy services |
A concrete example: during a call, headphones switch from A2DP to HFP, which also carries the microphone but at lower audio quality. That's why music suddenly sounds worse during a video call. It isn't a fault, it's the profile change.
Audio codecs
Bluetooth audio is always compressed. The codec decides how:
- SBC: mandatory and universal; quality varies depending on how it's configured;
- AAC: widely used on Apple devices; on Android results depend on the implementation;
- aptX and its variants: common on many Android phones, with low-latency or higher-quality versions;
- LDAC: aims for a high data rate; in environments crowded with radio signals it may drop to lower rates;
- LC3: the LE Audio codec, more efficient at the same quality.
The codec is chosen from those supported by both devices. On Android, the developer options show which codec is in use at any moment. In practice, the difference between codecs is less noticeable than the difference between headphones of different quality or a good in-ear fit.
LE Audio and Auracast
LE Audio moves audio onto the Low Energy side of Bluetooth, with the LC3 codec. It promises lower power consumption, better support for hearing aids and streaming to several devices at once. Auracast is the broadcast feature: one source streams audio to as many compatible headphones as want to listen, for example in a waiting room or a museum. Broadcasting requires the phone, the operating system and the headphones all to support it.
Latency, multipoint and other details
- Latency: the delay between picture and sound. For videos, systems compensate by syncing the picture; in games and with musical instruments the delay remains noticeable, and you need low-latency codecs or modes.
- Multipoint: the ability to stay connected to two sources, such as a computer and a phone, switching automatically between them.
- Range: depends on transmitter power, obstacles and the human body, which absorbs 2.4 GHz waves. A phone in a back pocket can be enough to cause dropouts.
When the connection misbehaves
A sequence of checks that solves most cases:
- turn Bluetooth off and on again on both devices;
- forget the device from the list and pair it again from scratch;
- check whether the headphones are still connected to another phone or computer;
- update the accessory's firmware through the manufacturer's app;
- move away from interference on the same band, such as a running microwave oven or very crowded Wi-Fi networks.
Bluetooth and privacy
Bluetooth devices broadcast signals that others can detect. Modern smartphones use random addresses that change over time to make tracking harder. It's still good practice not to leave accessories in pairing mode indefinitely and to remove from the list any devices you no longer use.
In short
- There are two Bluetooths: Classic for continuous audio, Low Energy for sensors and minimal power draw.
- Versions indicate possible features; what counts are the profiles and codecs supported on both sides.
- During calls headphones switch to the HFP profile and audio gets worse: that's normal.
- LE Audio and Auracast bring more efficiency and broadcasting to multiple listeners.
- For connection problems, pairing again from scratch solves most cases.
