High quality surround sound system from a single component? That’s a bit of a Holy Grail for the audio community. Just think how useful it would be – the scary bits that make you jump in movies coming from behind you even though your soundbar is in front? Freaky!
Those clever devils at Philips Consumer Lifestyle Innovation Lab (iLab), have developed something called The Ambisound Soundbar which you can integrate into your home theatre system. They argue that surround sound audio technology is about more than sophisticated algorithms and electronics; it is also about evoking emotion in the listener. “We started thinking about how to embrace the listener with sound without a room full of wires and speakers,” explains Georges Aerts, iLab Program Manager.
The result is the Ambisound Soundbar, a one-piece, integrated home theatre system that uses advanced digital sound processing technology to deliver multichannel surround sound. Aerts and his colleagues wanted to develop sound processing components that would produce a surround sound effect from a single device. In the past, iLab engineers designed audio components using analogue circuitry or by hand-coding DSPs in Assembler or C code. These approaches made it difficult to test out new ideas and techniques. In addition, there was no way for acoustic engineers to evaluate a new approach without investing a significant amount of time and resources in building a hardware prototype.
The iLab team needed a development environment that would enable them to rapidly evaluate design ideas and optimize them to perform within hardware constraints such as available RAM, program space, and processing power. They also needed a way to enable Philips marketers and product development teams to evaluate the concepts in real time and hear the effect of various parameters on audio output.
The answer came in the form of technology called Simulink, with which the engineers developed sound models and ran high level simulations that enabled them to quickly converge on the most promising algorithms. Using Signal Processing Toolbox, they applied infinite impulse response (IIR) filters as well as low-pass, high-pass, peaking, and shelving filters to improve sound characteristics – including voice intelligibility and deep bass performance.
The iLab team then implemented the algorithms on a DSP, adjusting them to fit within the DSP’s RAM or MIPS limitations. After testing the hardware implementation with the Ambisound Soundbar, the team returned to the Simulink model to further fine-tune parameters. The optimized parameters were extracted from the Simulink model using a MATLAB script and downloaded onto the DSP.