Can BLE be used for audio?
Bluetooth Low Energy (BLE), also known as Bluetooth Smart, is a wireless personal area network technology aimed at novel applications in the healthcare, fitness, beacons, security, and home entertainment industries. BLE was originally introduced in 2011 as part of the Bluetooth 4.0 core specification. It is designed for extremely low power consumption, resulting in long battery life for connected devices (Source).
The main advantages of BLE compared to classic Bluetooth are its lower power consumption, lower implementation costs, and support for connecting to the internet and sending data to cloud servers. This makes it ideal for connecting IoT devices and wearables. BLE is commonly used today in smartwatches, fitness trackers, medical devices, smart home appliances, location beacons, and industrial sensors.
BLE Basics
BLE (Bluetooth Low Energy) is a wireless personal area network protocol designed and marketed by the Bluetooth Special Interest Group. It is aimed at novel applications in the healthcare, fitness, beaconing, security, and home entertainment industries. Compared to Classic Bluetooth, BLE is intended to provide considerably reduced power consumption and cost while maintaining a similar communication range.
Some key technical specifications of BLE as summarized in the NXP BLE solutions document here include:
- Operates in the 2.4 GHz ISM band
- 1 Mbps data rate
- 2 MHz channel bandwidth
- Adaptive frequency hopping spread spectrum (AFH)
Compared to Classic Bluetooth, BLE has a lower power consumption, lower complexity, and lower cost. It achieves this through differences like a reduced duty cycle, optimized protocol stack, and fewer transmission channels.
BLE vs Bluetooth Classic
Bluetooth Low Energy (BLE) was introduced in Bluetooth 4.0 as a power-optimized version of Bluetooth technology. While Bluetooth Classic audio provides a bandwidth of up to 3 Mbps, BLE only has a bandwidth of 2 Mbps [1]. This lower bandwidth does limit audio quality and latency compared to Bluetooth Classic.
However, BLE’s focus is on providing long battery life rather than maximize audio performance. The lower bandwidth translates to lower power consumption so BLE devices can operate for months or years on a single charge, whereas Bluetooth Classic audio products may only last hours or days before needing a recharge [2].
In summary, while Bluetooth Classic Audio is better suited for wireless stereo music streaming, BLE provides a tradeoff of lower audio quality and latency for drastically improved battery life. BLE is not meant to replace Bluetooth Classic for premium audio applications.
BLE Audio Challenges
One of the biggest challenges with using BLE for audio is that audio requires high bandwidth, while BLE was originally designed for low bandwidth applications like sensors and smart home devices. The limited bandwidth of BLE makes it difficult to achieve high quality, low latency audio transmission [1].
BLE operates in the 2.4GHz band and uses 40 channels with 2 MHz spacing and data rates of 1 or 2 Mbps. In comparison, Classic Bluetooth audio profiles like A2DP use larger bandwidths like 44.1kHz for CD quality audio. Trying to stream high quality audio over a BLE link requires special techniques to deal with the limited data rates [2].
BLE was designed for small packet sizes appropriate for sensor data. Audio streaming generates much larger packet sizes that need to be fragmented across multiple BLE packets. Managing these fragmented audio packets adds complexity and overhead.
BLE Audio Codecs
The LC3 codec introduced with LE Audio is optimized specifically for transmitting high quality audio over BLE connections. LC3 stands for Low Complexity Communication Codec and was developed by the Bluetooth SIG to provide efficient compression and low power usage for Bluetooth audio applications.
Some key features of the LC3 codec include:1
- Supports a wide range of bitrates from 150 kbps to 512 kbps
- Frame interval options of 10 ms or 7.5 ms for low latency
- Good audio quality even at low bitrates
- Low complexity design optimized for BLE
By leveraging LC3, LE Audio is able to provide robust streaming of high quality music, voice, and other audio content over BLE at low power levels. This helps expand the possibilities for wireless earbuds, hearing aids, smart speakers and other audio devices that utilize Bluetooth connections.
Use Cases
BLE audio opens up new possibilities for wireless audio devices and systems. Here are some of the key use cases that are enabled by BLE audio:
Earbuds
True wireless earbuds can take advantage of the lower power consumption of BLE to enable longer battery life. Whereas Bluetooth Classic earbuds may last only 5-6 hours on a charge, BLE earbuds could potentially last 8-10 hours before needing to be recharged. The robustness of BLE connections also means fewer audio dropouts.
Speakers
Wireless speakers can leverage BLE audio for easy multi-room audio set up. Users can smoothly group multiple speakers to play audio in sync across rooms. Each speaker becomes a node in the network. This is far simpler than traditional multi-room systems.
Hearing Aids
Hearing aid manufacturers are looking at BLE for lower latency streaming between hearing aids and mobile devices. This enables advanced features like transparency mode and sound enhancement. BLE’s low power is also crucial for the tiny batteries in hearing aids.
Implementations
While BLE audio is still an emerging technology, some companies have started to implement it in audio products. For example, Audeze offers several headphones like the Audeze Penrose, Euclid, and Mobius that support Bluetooth 5.2 and the new LC3 audio codec for lower latency wireless audio over BLE.
As mentioned in discussions on Reddit (source), Audeze does not always promote the BLE capabilities prominently. Other companies like Turtle Beach also offer gaming headsets with Bluetooth 5.2 support.
On the silicon vendor side, companies like Nordic Semiconductor have BLE audio SDKs for their chips like the nRF5340, as noted on their DevZone Q&A forums (source). However, end consumer products leveraging these capabilities are still limited.
As the LC3 and other codecs mature and more Bluetooth audio devices adopt support for BLE standards, implementations will likely continue growing in the future.
Limitations
While BLE audio offers benefits over classic Bluetooth audio, it does have some limitations to be aware of. These primarily relate to audio quality, latency, and range.
In terms of audio quality, BLE audio is capable of up to 500 kbps bitrate using the LC3 codec, which is an improvement over classic Bluetooth’s 328 kbps with SBC. However, some users may still find this lower than wired headphones, and there can be some degradation if multiple connections are active (Bluetooth.com).
Latency is also a factor, as the encoding and transmission of BLE audio introduces lag. While aptX Adaptive can achieve < 40ms latency, standard BLE audio profiles have higher latency around 150-200ms. This could cause sync issues for video or gaming (NYTimes).
Finally, BLE has a typical range of up to 100 meters compared to classic Bluetooth’s 10-15 meters. However, audio quality can degrade at longer ranges as the signal gets weaker. Obstructions like walls can also impact range and reliability.
The Future
As Bluetooth LE Audio technology continues to develop, there is potential for further improvements to enable even better quality audio. The Bluetooth Special Interest Group (SIG) indicates several areas of ongoing research and development:
First, the LC3 codec could be enhanced to support even higher bitrates up to 512 kbps, compared to current up to 345 kbps, bringing CD-like quality.1 Further optimizations may also improve efficiency and audio quality within the current bitrate range.
Second, multi-stream audio transmission through Auracast broadcast audio could scale up to support an unlimited number of audio streams, rather than just 4 simultaneous streams today.2 This could enable new large-scale applications like streaming audio to an entire stadium of people.
Finally, updates to the LE Audio protocol itself could reduce latency and playback delay even further to improve synchronization between multiple audio sources. The target is under 10ms end-to-end latency.3
With these continued enhancements, Bluetooth LE Audio aims to become an increasingly versatile wireless audio standard for the future.
Conclusion
In summary, Bluetooth Low Energy can be used for audio applications, but has some limitations. The low bandwidth of BLE restricts audio quality, so it works best for simple use cases like voice commands, notifications, and short voice messages. More advanced audio applications may be challenging due to latency issues and audio compression needs. However, with the right codecs and implementation strategies, BLE audio can provide a convenient wireless option in certain scenarios. While it likely won’t replace Bluetooth Classic for high fidelity stereo audio, BLE audio opens up new possibilities for low power peripheral devices. With continued codec development and new use case discoveries, BLE has potential to become a viable wireless audio solution in the future.
