Bluetooth audio codecs: A guide to earbud audio quality

Smartphone manufacturers all but took away our beloved phones with headphone jacks. Now we’re left buying admittedly great wireless earbuds hand over fist. But listening to music is no longer a straightforward plug-and-play experience. Instead, we must ensure the buds support the same features as our smartphones to ensure the best audio quality. Wireless earbuds offer plenty of conveniences, but there’s some confusion around Bluetooth codecs. We’ll get you up to speed on everything you need to know about any Bluetooth audio codec. By the end of this, you’ll be able to match the right audio codec to your needs.

Do you make a point to consider Bluetooth codecs when buying headphones?

What is a Bluetooth codec?

A Bluetooth audio codec is a digital encoder and decoder that compresses audio data as it’s transferred from your phone to your wireless earbuds. Ideally, a source device (e.g. a smartphone) will send a high-fidelity audio signal to the receiver (e.g. earbuds) without dropping the connection.

Before we go further, here are some audio terms you will want to familiarize yourself with:

• Sample rate (Hz): The sample rate, or sampling frequency, indicates the number of times a file is sampled within one second. A common sample rate is 44.1kHz. This means the audio is sampled a bit more than twice the limit of human hearing (20kHz), exactly what you need for perfect audio capture. Higher sample rates will capture higher frequencies, but you can’t hear them.
• Bit depth (-bit): This denotes the number of bits of information (1s and 0s) in each sample. Common audio bit depths are 16, 24, 32, and occasionally 64-bit. A higher bit depth contains more information than a lower bit depth. Going from 16-bit to 24-bit audio doesn’t yield more accurate audio. Instead, this jump in bit depth increases the noise floor.
• Bitrate (kbps): The bitrate represents the number of bits processed in a unit of time (typically seconds). This is written as “kbps,” and a common bitrate. An uncompressed, 16-bit/44.1kHz audio file is 1,411kbps. There are diminishing returns with high bitrates.

When checking out your buds’ Bluetooth codec specs, don’t get too caught up in the “bigger is better” mentality. Humans cannot perceive anything above 16-bit/44.1kHz audio; we can only register that if we have perfect hearing. Considering hearing abilities decrease with age, it’s likely that you and I have some damaged stereocilia. On top of that, these high-bitrate Bluetooth codecs (24-bit or greater) are not always lossless. For now, most of us are stuck with lossy audio because of Bluetooth’s current bandwidth limitations.

Limited human hearing aside, transferring more data also risks creating an unstable connection. There may be a greater chance of interference if you’re in a busy area full of other people using wireless earbuds. A lower bitrate offers more connectivity headroom but also means the audio file is more compressed than a high bitrate file, but not all compression is equal.

When shopping for Bluetooth codecs, remember human hearing has its limits. Sometimes a stable connection is better than the highest bitrate.

Then there’s the issue of Bluetooth latency. Years ago, there was a marked variation between popular smartphones and their Bluetooth latency measurements. According to data from Google, the average latency of the most popular Android devices was 109ms in 2017 but the most popular phones in 2021 averaged 39ms. This is quite an improvement as most people can’t perceive latency less than 20ms, but latency is something to keep in mind, particularly for gaming.