Wednesday, April 22, 15:00 - 17:30, Location: Show and Tell Area A
Nay Oo, Woon-Seng Gan
This project is about the psychoacoustic audio bass enhancement system, developed in the Texas Instrument real-time DSP platform. There has been always a strong desire to improve the low frequency (bass) reproduction of the audio enable devices, such as MP3 players, mobile phone loudspeakers, and motor car audio systems, etc. However, due to the small size limitation of such devices, physical acoustic reproduction of low frequency (bass) is very poor. Basically, the small loudspeakers have inherent poor bass response. To enhance the bass by simply equalizing low frequencies does not work, and may even cause loudspeaker overload that can eventually damage the loudspeakers. However, there is a better way to enhance bass by tricking our human auditory systems. Such kind of systems is called the psychoacoustic bass enhancement systems. By making use of the phenomenon known as the "Missing Fundamental", which states that our auditory system can reconstruct the fundamental frequency from the harmonics even if the fundamental frequency is missing, we can trick our ears to hear low frequencies from their higher harmonics. In that sense, physical bass frequencies, which cannot be reproduced by the loudspeakers, can be replaced by the psychoacoustic bass frequencies that are synthesized in the human auditory system. Hence, virtually we can extend the low frequency bandwidth with psychoacoustic bass enhancement systems.
In this project, we make use of a memoryless nonlinear device (NLD) called Arc-Tangent Square Root (ATSR). ATSR can generate the strong harmonics which can be controlled with four parameters. The novelty of this algorithm is the ease of generating rich harmonics (both even and odd with controlled decay rate) that are suited for different genre of music. The real-time implementation is eased with converting ATSR to polynomials by interpolation. Texas Instruments TMS320C5509A DSP starter kit is used as a prototyping board to demonstrate this concept. We have also implemented different operating modes to compare and contrast the performance of the psychoacoustic bass enhancement system with other conventional bass enhancement approaches.