Just before Christmas, the Bluetooth SIG published the final documents in the first release of Bluetooth LE Audio. It’s been the largest single development in the history of the Bluetooth specifications, taking around eight years and comprising 25 new or updated documents, with over 1,250 pages of specification. Its aim is ambitious, the intent being to provide the platform for the next twenty years of wireless audio development.
Wireless audio has evolved at a bewildering pace. Back in the late 1990s there were a few proprietary solutions for wireless headphones and some rudimentary adaptors that you could plug into the base of a mobile phone, but the 3.5mm socket and a wired headset was the accepted way to connect your ears to any electronic source of music.
Although Bluetooth started with the desire to cut the cable, it took time to change people’s minds, which often needed external stimulus. Sales of handsfree headsets only began to take off when Government legislation around the world began to make it illegal to hold a mobile phone whilst driving. That persuaded phone manufacturers to include Bluetooth chips in their phones, which put in place the foundation for Bluetooth’s dominance in wireless audio.
The figure below shows the successive growth phases. The A2DP profile supported streaming of stereo music, but it wasn’t until music streaming services like Pandora and Spotify began to emerge that anyone began buying Bluetooth stereo headsets. From 2011 to 2016 sales of Bluetooth headphones closely mirrored the growth of Spotify subscribers, showing that content pulled sales of wireless headsets, rather than vice versa. In 2016, Apple launched AirPods and everything changed again, with True Wireless Stereo earbuds becoming the fastest selling product ever. Just five years later, 2021 saw between 300 and 400 million Bluetooth earbuds shipped, although that growth is beginning to slow.
Bluetooth LE Audio is poised to kickstart another phase in audio applications. It builds on the applications which are already successful in the market. For products like earbuds and hearing aids, it removes the need for the proprietary extensions which are required for today’s True Wireless Stereo earbuds, leading to full interoperability between products and applications. It includes a new, state of the art codec, called LC3, which provides excellent audio quality and higher efficiency. That, along with the power savings available by running over Bluetooth LE, means that designers have more freedom in their designs, being able to offer longer battery life, or enhanced audio processing. It also allows much lower latencies to be used, so that a Bluetooth LE audio signal can be used alongside a normal acoustic path.
However, the real game-changer with Bluetooth LE Audio is the introduction of a broadcast capability. At its simplest, this allows a transmitter to send the same audio streams to multiple devices. That could be a public announcement, such as travel information. It could equally be an app which lets you share streamed music on your phone with your friends. The public use case is very similar to what hearing aid wearers can do today with the inductive loop telecoil system, but Bluetooth LE Audio means that this capability can be extended to high quality music. It’s simple to install, so any venue, such as a gym, bar or coffee shop can provide multiple audio streams for their customers.
These broadcast streams carry metadata to describe their content. This allows users to select what they want to hear, but can also be used by apps to detect public audio broadcasts to add location specific information, opening up the possibility of audio augmented applications. The broadcast streams can also be encrypted and authenticated, so that they can be used for ad-hoc, private conversations, such as talking to someone at a ticket desk or hotel reception.
The new Bluetooth LE specifications include an incredibly wide range of applications. The industry support has been excellent, with multiple silicon vendors offering compliant chips for transmitters (typically phones, TVs and independent broadcast devices) as well as for earbuds, headphones and speakers. The underlying Core features were introduced in the 5.2 release, which means that many devices are already hardware capable. Although it always takes time from the adoption of a wireless standard to products and applications appearing in the market, in the case of Bluetooth LE Audio, it looks as if we will see the first products appearing very soon.
I’ve been involved in the development of Bluetooth LE Audio from its inception and am excited about what it offers. To introduce people to the possibilities, I’ve just published a book to help explain how the various specifications fit together and present the potential applications. It’s called “An Introduction to Bluetooth LE Audio” and is now available for purchase in paperback or hardback from Amazon. The Bluetooth SIG will also be making a digital version of the book available for download from the www.bluetooth.com website.
Over the coming months, I’ll be writing more about the potential use cases and market opportunities for Bluetooth LE Audio on my blog at www.nickhunn.com.