How pairing works
Bluetooth is a short-range radio standard that lets two devices talk without a cable. Pairing is the first-time introduction. You put the earbuds in pairing mode, usually by holding a button on the case, and then select them on your phone’s Bluetooth list. The devices exchange information and agree on a shared secret key, which is used to encrypt what passes between them. They remember each other afterwards, so reconnecting is automatic when both are nearby.
Earbuds can usually remember several devices, but connect to only one or two at a time. Some models offer “multipoint” connections, which let them stay linked to a phone and a laptop at once, switching when audio plays from either. Features like automatic switching or quick pairing pop-ups are often built by the phone or earbud maker on top of standard Bluetooth, so they may work only within one company’s products.
Typical troubleshooting is simple: forget the device in the phone’s Bluetooth settings, put the earbuds back in the case, and pair again. Keeping the phone’s software current also helps, since Bluetooth behavior is part of the mobile operating system.
Range and interference
Bluetooth earbuds are designed for a few meters, and walls, bodies and crowded radio environments reduce reliability. Bluetooth uses the 2.4 GHz band, the same busy band that many home networks and microwaves use, so you may hear dropouts in places with lots of wireless traffic. Wi-Fi bands are discussed elsewhere, and the overlap is one reason crackling is common in crowded stations.
Earbuds also have to relay audio between the left and right bud. Some designs send to one bud, which forwards to the other, while newer ones connect to both more directly. Either way, a bud placed in the case or lost out of range can cause the audio to drop.
What a codec does
Audio has to be compressed to fit through the Bluetooth link. A codec is the method that squeezes the sound at the sender and rebuilds it at the receiver. Different codecs make different trade-offs between quality, delay and reliability.
- SBC is the basic codec that all Bluetooth audio devices support. It is dependable and gives acceptable sound for most listening.
- AAC is commonly used on Apple devices and some others, and often performs well for music.
- Other codecs such as aptX variants and LDAC are offered by some Android phones and earbuds. They can transmit more detail or lower delay, but only if both the phone and earbuds support the same one.
The codec in use is whichever the two devices agree on, so a premium codec on the earbuds does nothing if the phone does not support it. Whether the difference is audible depends on the music, the earbuds and your ears, and many listeners struggle to hear it in everyday settings. The same question applies to streaming files: the source quality matters, as covered in the article on audio quality.
Delay (latency) is a related point. Bluetooth adds a short lag. For music it hardly matters, but in video or gaming the picture and sound can drift apart. Most video apps compensate automatically, and some earbuds include a low-latency mode for games.
Battery life
Earbuds have tiny batteries, so manufacturers quote hours of listening per charge and extra charges from the case. Real life differs from the headline figure for several reasons.
- Turning on noise cancelling or spatial audio uses more power, so quoted times are often for the most frugal settings.
- Volume level matters. Loud listening drains more.
- Calls with microphones active use more power than music.
- Cold weather reduces the capacity of lithium batteries temporarily.
- Batteries age. After a couple of years of regular use many earbuds hold noticeably less charge, as with phone batteries described under battery health. Because the cells are small and usually sealed in, they are often hard or impossible to replace, which is a consideration for longevity.
A case with its own battery lets you top up earbuds several times. Charging in the case also reduces how often you handle the earbuds themselves.
How noise cancelling works
Active noise cancelling, often shortened to ANC, uses microphones on the outside of the earbud to listen to surrounding sound. A processor then produces a signal that is the mirror image of that noise. When this “anti-noise” plays through the speaker, the two waves partly cancel each other, so you hear less of the background.
This works best on steady, low sounds such as engine hum, air conditioning or the rumble of a train. It is weaker for sudden or high-pitched sounds such as speech or clattering, which change too quickly to cancel neatly. A good seal in the ear also provides passive isolation, so fit and the right ear tip size make a large difference.
Many earbuds also have a transparency or ambient mode, which does the reverse and pipes outside sound in through the microphones. That is useful for hearing announcements or traffic. For safety, remain aware of your surroundings when walking or cycling.
Noise cancelling may leave an odd sense of pressure for some people, which varies from person to person.
Choosing and caring for earbuds
- Check which codecs your phone supports before paying extra for a premium one.
- Try different ear tip sizes, as comfort and seal affect both bass and noise cancelling.
- Look for a water or sweat resistance rating if you plan to exercise, and remember such ratings do not make a device waterproof forever.
- Wipe the mesh and charging contacts gently, since earwax and dirt cause many faults.
- Keep volume at a comfortable level. Listening very loudly for long periods can harm hearing.
- Consider that some earbuds contain sensors for motion or pulse, which brings them into the world of wearable devices and the data that goes with them.