OpenSynergy’s Voice SDK is an audio processing software that provides a significant voice quality enhancement in hands-free voice applications. It enables manufacturers to implement voice band audio processing for automotive hands-free telephony and speech recognition in their cockpit devices.
It comprises noise reduction, full-duplex echo cancelling and optional dual microphone array-technology for directional microphony. The Voice SDK library has a simple API and can easily be integrated into any operating system. The combined offer of Voice SDK and Blue SDK provides a complete infotainment voice processing chain.
Acoustic Echo Cancelling
Acoustic Echo Cancelling (AEC) is one of the key components of Voice SDK. It is an extremely robust solution realizing full-duplex communication in a wide variety of use cases. It enables a VDA-compliant hands-free system with an Echo Return Loss Enhancement (ERLE) of at least 45 dB. Fully linear echo cancelling is combined with non-linear processing (residual echo suppression), maintaining full-duplex operation to the greatest possible extent.
Single Microphone Noise Reduction
Noise Reduction (NR) is the second core algorithm of an automotive hands-free SDK. With only one microphone, NR is capable of attenuating stationary or slowly modulating noise components up to 20 dB. This is achieved by a proprietary algorithm, which is capable of distinguishing between voice components and slowly modulating noise components, which are typical for automotive hands-free applications. The level of noise attenuation in dB is a tune-able parameter.
With two microphones, noise reduction can be further enhanced compared to a single microphone solution. The second microphone provides spatial information about situations of both voice signal and disturbances that come from different directions. As a result, non-stationary disturbances like interfering voices can be efficiently reduced. OpenSynergy offers different variants of array technologies for different microphone spacings and microphone types (conventional cardioid ECMs or modern MEMS microphones).
Additional Components of Signal Processing
A configuration and diagnostic link is very useful as tuning and monitoring interface, in order to check signal qualities in the digital domain, and to set parameter values (e.g. equalizer settings). OpenSynergy suggests a proprietary Bluetooth link to a PC for fast and convenient data exchange with the hands-free system. On the PC, a Graphical User Interface (GUI) is provided that helps to tune the system and – to a certain degree – can even perform an automatic assessment of hands-free operation quality.