Bluetooth LE Audio Set to Tune Up the Hearable Experience
After years of refinement, the specifications for Bluetooth LE Audio are finally ready for mainstream adoption.
The shift from wired to fully wireless devices has been largely powered by improvements in Bluetooth and Bluetooth Low Energy (BLE).
Bluetooth Classic uses its radio continuously for higher throughput while Bluetooth Low Energy uses its radio for the shortest time possible for low power.
Now, the Bluetooth Special Interest Group (SIG) has announced the biggest update to Bluetooth technology in years with the completion of the Bluetooth LE Audio specifications. In this article, we’ll look at the new specification to see what BLE Audio may bring to the next generation of audio devices.
The Bluetooth LE Audio Architecture
Like previous specifications before it, the Bluetooth LE Audio architecture has been built in several layers.
As explained in the Bluetooth LE Audio guide, the bottom layer of the architecture is known as the Core, consisting of the radio and Link Layer. These two components together make up the Controller and physically send the Bluetooth packets over the air.
The Bluetooth LE Audio architecture. Image used courtesy of Bluetooth SIG
The layer above the Core is the Host, which tells the Core what to do for any given application. On a system level, keeping the Host and the Controller separate from one another is an artifact of historical design, but on the hardware level, the Host and Controller are often integrated into a single IC.
Within the Host exists one of the new structures to BLE Audio known as the Generic Audio Framework (GAF). The GAF is an audio middleware consisting of all of the generic functions that are likely to be used by more than one audio application.
Finally, at the top of the stack are the Top-level Profiles, which add specific information to the GAF specifications.
L3C Codec: Better Sound With Lower Power
One of the new features introduced by BLE Audio is the low complexity communications codec (LC3).
Audio codecs are a fundamental part of a specification's performance; the codec’s role is to compress the audio stream at the source and decompress it at the receiving end. Compared to other available codecs, the LC3 codec is considered one of the most advanced available.
Performance comparison of SBC and the LC3. Image used courtesy of FORCE Technology, Sense Lab and Nordic Semiconductor
Some of the important specs to know for the LC3 codec include:
- Support for 10 ms or 7.5 ms frame sizes
- Bit depths: 16, 24, and 32 bits per audio sample
- Sampling rates: 8 kHz to 48 kHz
- Bitrates: Up to 400 bytes per frame
Bluetooth SIG compares L3C to Bluetooth Classic’s SBC codec because it can compress the same 1.5 Mbps audio stream to a 160 Kbps stream (compared to SBC’s 240 Kbps). L3C achieves this while significantly reducing audio impairment, according to Bluetooth SIG.
LC3 features. Image used courtesy of Bluetooth SIG
L3C codec is reported to have lower power consumption than previous Bluetooth generations while improving—not sacrificing—audio quality. This feature may be especially important in wearable designs, where less power means smaller batteries and longer battery life overall.
According to Nordic Semiconductor, Bluetooth LE Audio's LC3 codec offers more effective audio stream compression and on-the-fly packet-loss concealment to avoid skipping. The codec achieves this by leveraging the processing power of modern chipsets.
Auracast Shares Audio With Unlimited Number of Users
Another important feature BLE Audio offers is a new functionality called Auracast.
Auracast allows BLE Audio transmitters to broadcast one or more audio streams to an unlimited number of audio receivers. First, an Auracast transmitter broadcasts several advertisements, providing an Auracast assistant with information about the broadcast.
Working principle of Auracast. Image used courtesy of Bluetooth SIG
The Auracast assistant, like a smartphone, will then scan for Auracast advertisements and present a user interface that allows users to join broadcasts—similar to the UI used by Wi-Fi networks in public spaces. Alternately, users can connect to Auracast by scanning a QR code or tapping an NFC-enabled surface. Finally, an Auracast receiver, such as headphones, can find and select which Auracast streams it would like to participate in.
What Does Bluetooth LE Audio Mean for Users?
The Bluetooth SIG expects BLE Audio to offset a wave of new use cases for wireless audio. For one, the new specification has added support for hearing aids and implants.
With Auracast, users can also share audio experiences with an unlimited number of other users. For example, a public television can be muted to avoid disturbing occupants of the room while still allowing those interested to hear the audio on their personal headphones. Bluetooth SIG cited a few specific examples that this feature could be of use: gym-goers connecting to a central TV, individuals sharing Bluetooth audio with friends nearby, theater attendees playing audio to personal headphones, and people making password-protected closed audio feeds.
The BLE Audio specifications are also said to support true wireless earbuds, meaning that each individual earbud will maintain its own connection to a source device. According to Bluetooth SIG, BLE Audio will also better manage packet loss, so the audio sounds better when a user is further from the source device.
Plans for Market Availability
While Bluetooth SIG has noted that some existing devices can be updated to support Bluetooth LE Audio, the group has not yet clarified whether consumers of older hardware will need to buy new devices to tap into the benefits of the new specs.
No products on the market currently advertise as having BLE Audio capability. Even so, Bluetooth SIG reports that the first compatible devices may appear on the market in the coming months with wider availability anticipated at the end of 2022.