Introducing Bluetooth LE Audio | Electronic design


What you will learn:

  • Benefits derived from the new Bluetooth LE Audio standards and specifications.
  • The arrival of Bluetooth audio streaming.
  • An overview of how broadcast streams work.

Over the past 20 years, Bluetooth wireless technology has become the standard for personal audio. From its initial use in headsets for hands-free mobile calling, it has encompassed high-quality music streaming, which has become increasingly popular with the growing availability of smartphones and streaming apps. The arrival of Apple’s AirPods and the resulting craze for headphones have made it the fastest growing consumer product sector we’ve ever seen.

Now, the Bluetooth SIG has just launched its new set of Bluetooth LE Audio standards. It consists of a comprehensive set of specifications designed to support the next 20 years of audio development, enabling the industry to deliver even more product and application innovation.

The demands of the hearing aid industry prompted the development of Bluetooth LE Audio. Although distinct from the consumer audio market, hearing aids had to address many issues that still plague consumer headphones.

Because they are worn all day, without the possibility of recharging, they have to operate with little energy. In many cases, users can wear different hearing aids in each ear, which most of today’s true wireless stereo (TWS) headphones don’t allow because they rely on proprietary methods to keep the headphones in sync with them. with each other.

Finally, hearing aids support streaming systems, where multiple wearers can connect to the audience, inductive loop systems known as telecoil.

All of these features have tremendous utility for everyday audio use cases, but they had fallen into the “too difficult” category. It was also apparent that the existing Bluetooth audio specs were limited, with the hands-free profile designed primarily for cellular calls and the A2DP specs limited to streaming music to a single set of headphones or earphones.

Recent developments, such as voice assistants and the emergence of spatial audio and augmented reality, have clearly shown that much more flexibility is needed. This prompted the industry to come together to deliver Bluetooth LE Audio to support a new generation of audio applications.

Database update

At the heart of the new specifications is the decision to use Bluetooth Low Energy, launched in 2010 as a much lower power option, aimed at devices such as wearables and health sensors. It has now been extended to support multiple audio streams.

The standard introduced a new audio codec, LC3, to further reduce audio power. The LC3 has been optimized to support voice and music applications, delivering the same subjective quality as current audio codecs at around half the bit rate. This means that smaller amounts of information have to be transmitted, reducing power consumption and reducing the likelihood of interference from other radio sources.

Designers can use this new flexibility to reduce power consumption and increase battery life. Alternatively, they can transmit multiple streams for spatial audio, support multiple languages, or use the additional resources they’ve acquired for more efficient audio algorithms, like noise suppression.

Audio broadcasting: a new user experience

These features enhance today’s wireless audio experience, but the real game changer introduces streaming capability. In its simplest form, this allows a transmitter to send the same audio streams to multiple devices. Ever since Sony’s Walkman arrived in 1979, friends have shared headphones to listen to music. With Bluetooth LE Audio, you can truly cut the cords, allowing any number of people to listen to the same audio stream.

However, it’s not just about sharing personal music from your phone.

The audio broadcast may be used for public announcements, such as travel information. This is a similar use case to what hearing aid wearers can experience today with the inductive loop telecoil system. With Bluetooth LE Audio, this capability can be extended to high-quality music received by any LE Audio headset or hearing aid.

These broadcast transmitters will be inexpensive and easy to install. Therefore, any venue, such as a gym, bar, or cafe, can provide multiple audio streams to its customers, either as background music or to provide audio to accompany multiple TVs.

Finding and connecting to these streams is simple and requires no pairing. These broadcast streams include metadata that describes their content, allowing users to select what they want to hear if there are multiple different broadcasters.

In the same way that phones can detect Wi-Fi hotspots, a similar scan can provide a list of streaming audio within range. (see picture). Clicking on any streaming source would switch your headphones to receive the selected audio stream. The audio would go directly from the streaming source to your headphones – the phone only acts as a controller, essentially becoming a remote control.

Broadcast streams can also be encrypted and authenticated, making them preferred for ad-hoc private conversations, such as talking to someone at a counter or hotel reception. This means you’re likely to wear an earbud longer, much like a hearing aid user; thus, LE Audio’s low power consumption is particularly beneficial.

Because the broadcasts are one-way, they take advantage of the higher link budget from an infrastructure transmitter to the listener (the reverse link budget is limited by power constraints and antenna size in a headset or hearing aid). The range is therefore significantly greater than conventional Bluetooth or Wi-Fi. Therefore, a single broadcast transmitter can cover large rooms and large halls.

Extended support

The new Bluetooth LE specifications support a wide range of applications. Industry support has been excellent, with several silicon vendors offering compliant chips for transmitters (typically phones, TVs, and independent streaming devices) as well as earphones, headphones, and speakers.

The underlying Core features were introduced in version 5.2, which means that many devices are already compatible with the hardware. Although it always takes time between the adoption of a wireless standard and the appearance of products and applications on the market, in the case of Bluetooth LE Audio, it seems that we will see the first very soon.

To provide more detailed information, I have just published a book to help explain how the various specs fit together and outline potential applications. Called “An introduction to Bluetooth LE Audio“, it is now available in paperback or hardcover on Amazon. A digital version is also available for download from the Bluetooth SIG website.


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