Bluetooth® audio testing

Bluetooth® voice communication and audio streaming

Overview of Bluetooth® audio

Wireless audio transmission is one of the primary applications of Bluetooth®, and today, billions of headphones, speakers, mics and earbuds use Bluetooth® BR/EDR connection. Synchronous links (SCL) allow for interactive speech communication, and asynchronous links (ACL) enable audio streaming and recording applications. Key Bluetooth® profiles for audio are the headset profile (HSP), the hands-free profile (HFP) and advanced audio profile (A2DP).

Differences between Bluetooth profiles

Differences between Bluetooth® profiles

Bluetooth® audio devices use different codecs, depending on audio quality requirements and connectivity limits. For speech communication, the continuously variable slope delta (CVSD) modulation codec is utilized, striking a balance between low latency, low data rate and acceptable audio quality. Meanwhile, the Bluetooth® Special Interest Group (SIG) mandates the use of a low-complexity subband codec (SBC) for more advanced audio applications. In addition, there are a variety of vendor-specific codecs, such as AAC, aptX or LDAC, which are also commonly supported.

Bluetooth® Low Energy Audio

Bluetooth® Low Energy (LE) Audio was initially designed for low-power, best-effort communication, perfect for connecting wearables or peripherals with small data packets. With Bluetooth® 5.2, the Bluetooth® SIG paved the way for the future of Bluetooth® LE Audio by introducing different types of isochronous streams: connected isochronous streams (CIS) and broadcast isochronous streams (BIS). CIS is ideal for audio streaming between a single source and a single sink, while BIS enables the broadcast of audio streams from a single source to multiple sinks. This evolution also brought forth a new, low-complexity communications codec (LC3), which offers a high level of flexibility and strikes a good balance between high audio quality and low data rate.

Different types of isochronous streams

The groundbreaking features of Bluetooth® LE Audio usher in a new era, expanding support beyond basic speech communication and audio streaming. Now, high-quality audio streaming and recording are possible, featuring multiple synchronized streams to facilitate applications like hearing aids. Additionally, the introduction of audio broadcasting, also known as AURACAST®, opens up exciting possibilities for public audio scenarios. Imagine tuning into a silent TV at a restaurant, receiving public announcements at a train station through your earbuds or immersing yourself in a live music performance for an exceptional listening experience even in noisy environments. Such a reality is already in the near future.

High-performance Bluetooth® audio test solutions

High audio and speech quality are paramount for delivering an exceptional mobile user experience. Bluetooth® wireless testing, coupled with comprehensive audio performance measurements, is key to accelerating the development of Bluetooth® audio devices.

Rohde & Schwarz test and measurement solutions are designed to comply with the latest Bluetooth® core specifications. Bluetooth® test functions are embedded across all major Rohde & Schwarz test instruments, including signal generators and analyzers. Our solutions cover Bluetooth® BR, EDR and LE and are suitable for the entire development cycle - design, certification and production.

The R&S®CMW500/270 serves as an ideal foundation for Bluetooth® audio testing, offering support for the most crucial audio profiles, mandatory codecs (CSVD, SBC, LC3), and a range of options for conducting audio performance measurements. These measurements include single and multi-tone assessments of output power, signal-to-noise ratio (SNR), total harmonic distortion (THD) and signal-to-noise and distortion (SINAD), among others, providing a holistic evaluation of audio device performance. It has the unique capability to seamlessly integrate Bluetooth® RF testing with audio testing, and it features in-radio test control for DTM-like testing of Bluetooth® LE devices in an over the air (OTA) setup.

This setup enables the simultaneous verification of audio performance and wireless Bluetooth® connection. It also provides the flexibility to experiment with various communication parameters. There is also the option to integrate an applicable audio quality measurement equipment for more advanced audio quality measurements, such as perceptual objective listening quality analysis (POLQA) or perceptual audio quality measurement (PEAQ). Additionally, the system supports an echo mode with a Bluetooth® loopback - ideal for functional testing in manufacturing.

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