Bluetooth audio codecs explained for headphones and speakers

Love it or hate it, Bluetooth has completely changed the way we listen to music! Since the first Bluetooth-capable device went on sale in the late 90s, the technology has popped up everywhere. Today, it’s a staple on everything from speakers to smartphones.

Like most people, I didn’t give the technology behind Bluetooth a second thought. But then, the market became flooded with cheap gear. Unfortunately, that’s opened up the doors to some awful sound quality.

I knew that if I wanted to enjoy the technology without sacrificing the listening experience, I had to learn a bit more about how Bluetooth worked. That’s when I learned more about Bluetooth audio codecs

Come to find out, Bluetooth is a lot more complex than I could have ever imagined.

How Does Bluetooth Send Audio Wirelessly?

The first thing to understand is how Bluetooth works! While it’s most commonly associated with music, the technology is used to send any type of data. It’s a low-power method of data communication with no line-of-sight issues.

So, how does it help audio travel wirelessly? Well, it all comes down to complex communication.

Bluetooth operates on low-power radio waves. More specifically, it operates around the frequency range of 2.45 gigahertz. When two devices connect via Bluetooth, they agree to exchange files in the same format. This is key here. This is where the audio codecs come into play.

Once connected, your files are sent over these radio waves in less than a second. If you’re wondering why Bluetooth speakers and headphones rarely experience interference, it’s because the transmitter changes frequencies over 1,500 times a second!

Both the transmitter device and the receiver device, also known as the “sink” hop around frequency bands together in a small personal network.

What Exactly Are Bluetooth Audio Codecs?

Audio codecs are the most important piece of the Bluetooth puzzle! Basically, a codec is a complex algorithm that prepares the data for wireless travel.

Ever wonder what codec actually means? It’s a portmanteau of compression and decompression. You could also think of it as coder and decoder. Whatever you refer to it as the term perfectly describes what’s going on under the hood.

You see, files need to be compressed to travel wirelessly. Large uncompressed files would take ages to travel via radio waves. While that’s fine for non-media, it would create lag in the streaming environment.

Codecs make that compression and decompression possible. On the transmitter end, the files are compressed into a specific file format. Once the sink device receives them, the files are decompressed so that they can be used.

Do Bluetooth Audio Codecs Affect Audio Quality?

As Bluetooth technology has evolved, several codecs were established. Audio files come in a wide range of formats. Some are already heavily compressed for easy distribution.

Bluetooth codecs are considered to be “lossy.” This means that they discard audio that’s less likely to be detected by the human ear. Codecs are quite advanced in this regard.

They utilize psychoacoustics to determine which parts of the frequency spectrum matter and which don’t.

To make matters even more complicated, codecs vary dramatically when it comes to the bit rate, bit depth, and sample rate. Bit rate refers to the number of bits processed per second. You can look at it as the speed of data transmission.

Meanwhile, bit depth and sample rate refer to the resolution of the audio. A higher sample rate and bit depth pick up more information, resulting in much larger files. For reference, the standard CD format is 16-bit and a sample rate of 44.1 kHz.

All that sounds confusing, but it matters when you’re talking about the capabilities of specific codecs. Not all audio codecs can handle high bit depths and sample rates. Theoretically, this could affect the quality of your music.

Another big factor is the bit rate, or data transmission speed. While wireless audio seems near-instant, it still takes time to travel. A higher bit rate can lead to noticeable latency issues. This isn’t a huge problem when you’re just listening to music. But the moment you add audio into the mix, it becomes glaringly obvious.

Ultimately, Bluetooth codecs can affect audio quality. That said, you probably won’t notice major differences in most situations. It’s only in those extreme circumstances that you might want to consider making a change.

For the most part, the quality of your headphones or speakers that has a greater effect on audio than the Bluetooth technology itself.

Types of Codecs and Their Characteristics

There are several Bluetooth codecs available. Most devices support more than one, allowing you to switch based on your needs. Here are some of the most common.

SBC

The original Bluetooth standard, this codec is found in virtually every device. Most connections default to SBC if no other shared codecs are supported. Bit rates are as high as 345 kbps and latency is usually between 200 and 300 milliseconds.

AAC

AAC is like an advanced version of standard MP3. Used by all Apple devices, AAC has a maximum transfer rate of 250 kbps. The cool thing about AAC is that is can be used without affecting sound quality. For example, if you are using an AAC streaming service with an AAC device and AAC speaker, wireless travel doesn’t impact quality.

Qualcomm Codecs

Qualcomm has developed several codecs that are used by Android phones. These include aptX, aptX HD, aptX LL, and aptX Adaptive.

Standard aptX has high bit rates around 352 kbps and low latency around 120 milliseconds. aptX HD takes things up a notch by bumping up transfer rates to 576 kbps or more. aptX LL, or aptX Low Latency, decreases latency below 40 milliseconds to prevent lag.

Finally, there’s aptX Adaptive. This is a newer codec that blends the features of all of the previous codecs into one. It adjusts performance based on your needs.

LDAC

Created by Sony, the LDAC codec has the highest bit rate of them all. Transfer speeds can be as high as 990 kbps. Thus, it’s a good choice for high-resolution audio.

LC3

LC3 is going to be the new Bluetooth standard. It’s a vast improvement on the SBC codec and is said to achieve better sound quality by using less power.

Conclusion

The differences you’ll hear between audio codecs are very subtle. But, there are instances in which you might want to consider which one you’re using. Understanding how Bluetooth codecs work and how they differ is important. That knowledge will help you choose the best gear possible and ensure that all your bases are covered regardless of what you’re listening to!            

Chris Wilson

Chris is one of the guys behind HeadphoneSelection.com. He is an Electronics Engineer by profession and he enjoys expressing his real-life experiences with technology and sharing it with others.