Wireless Audio Quality

Digital Signal Processing (DSP) can greatly improve the audio quality in Bluetooth devices.

Bluetooth DSP back in the day

In 2007, CSR added a new compression technology to its powerful DSP-based BlueCore5-Multimedia platform, which offered its customers much improved wireless audio quality. By porting APT's enhanced apt-X algorithm onto the BlueCore Multimedia platform, CSR offered yet more ways for wireless audio designers to create devices that offered improved levels of audio quality, with reduced processing latency compared to the Bluetooth standard SBC encoding, without compromising on power consumption. Unlike other Bluetooth single-chip devices, BlueCore5-Multimedia was based on a powerful Kalimba DSP coprocessor operating at 64 MIPS to support the integration of third-party software enhancements. The enhancements included dynamic noise and echo cancellation, stereo music enhancement, and text-to-speech capability. apt-X technology was an established standard for audio transport in the fields of professional broadcast and film post-production. Now, as regular listeners became more sophisticated, demanding higher quality on their mobile media players, additional channels for stereo headsets, and the ability to interact with video, the consumer market also benefited from apt-X.

Bluetooth DSP today

1. Noise Reduction: DSP algorithms can help reduce the amount of noise in a signal, improving the overall audio quality. This is particularly useful in Bluetooth devices, which can be susceptible to interference from other wireless devices.
2. Echo Cancellation: DSP can be used to detect and remove echo from a signal. This is especially useful in applications like Bluetooth headsets, where the proximity of the microphone to the speaker can often cause echo.
3. Equalization: DSP can be used to adjust the balance between different frequency components of a signal. This allows the sound to be tailored to the listener's preferences or to the acoustics of the environment, which can greatly improve the perceived audio quality.
4. Compression and Decompression: Bluetooth audio needs to be compressed to be transmitted effectively, as the bandwidth of Bluetooth is not sufficient for uncompressed audio. DSP algorithms are used to compress the audio in a way that minimizes the loss of quality, and then to decompress it on the receiving end.
5. Advanced Codecs: DSP enables the use of more advanced audio codecs, such as AAC and aptX, which provide better audio quality than the standard SBC codec that's used in many Bluetooth devices. These codecs use complex algorithms to compress and decompress audio in a way that retains more detail and reduces artifacts.
6. Beamforming: In devices with multiple microphones, DSP can be used to focus the pickup pattern of the microphones in a certain direction, which can help to isolate the sound source and reduce background noise.

Although DSP can improve the audio quality of Bluetooth devices, even today it also introduces a small amount of delay, which can potentially cause problems in applications where latency is critical. However, advances in technology are steadily reducing this latency, and it is generally not noticeable in most applications.