Active Noise Control for MRI noises: Active Method is used to control the noises generated by MRI scanning to eliminate the negative influence for medicla diagnosis and patients' hearing. My tasks involve incorporation of psychoacoustic factors and solving nonlinear problem.
Digital Audio Restoration: Corrupted audio is restored by using AR model prediction. Real-time system is implemented by using PADK board based on TI DSP.
Music Injection for Subjective Speech Enhancement: We aim to improve the speech from the perspective of human being's sensation by inserting music into noisy speech processed by the spectrum subtraction method.
Blind Dereverberation: Reverberation degrades the performance of ANC. Linear Prediction method is adopted to eliminate the reverberation based on SIMO model.
Problem: Audio may be corrupted due to damage of recording media (CD, tape, etc.) or communication interference
Algorithm:
AR model is used to predict corrupted signal
Both preceding signal and succeeding signal are used for prediction for more natural restoration
Two versions of prediction are combined using crossfade function
P. A. A. Esquef, "Interpolation of long gaps in audio signals using line spectrum pair polynomials," Helsinki University of Technology, Tech.Rep, vol. 72, 2004.
Flow Chart:
Demo system:
Algorithm is implemented with PADK (Professional Audio Development Kit) based on TI tms320c6727 DSP.
Presentation:
Digital audio restoration and real-time DSP implementation [Slides]
Music Injection for Subjective Speech Enhancement
Problem:
Conventional noise reduction methods improve the SNR of speech signal. However, the residual noise makes the speech annoying.
Our Idea:
Music Injection is adopted to reduce the negative effect of residual noise and improve the pleasantness of speech.
Volume of the injected music is adjusted adaptively.
An objective pleasantness model is utilized to evaluate the performance quantitatively.
Subjective test is also carried out to verify the validity of the above pleasantness model.
Flow Chart:
Publication: H. Bao, I. Panahi, P. Loizou, Y. Hu, "Music Injection For Subjective Speech Enhancement And The Psychoacoustic Pleasantness Analysis", Proceedings of the Sensor, Signal and Information Processing (SenSIP) Workshop, Sedona, AZ, May 11-14, 2008 [PDF][Poster]
Blind Dereverberation
Room reverberation degrades the performance of ANC. We will add dereverberation into the system to improve ANC performance.
This system, funded by China 613 Research Institute with $70,000, aims to improve the image quality of the airplane’s back cockpit. In especial, the instrument board is recognized by color with Ostu's method. I'm responsible for algorithm designing and software developing.
Software: MFC and VFW is utilized to process real-time video signals from capturing board.
Hardware: the system is implemented with a 12-layer board based on AD21160 DSP.
Direction Finding System
Direction Finding is important for Radio Supervision Department. Analog product is found instable in practical use. In this project under the contract with an electronic compnay, we aim to development a digital system based on DSP techniques to fullfill the Direction Finding fast and accuratedly. I'm responsible for algorithm designing, software developing and board debugging. It has now been put into mass production.
Algorithm: Digital phase detecting algorithm is developed based on the 90 degree phase-shift of Hilbert transform to detect the phase difference of two coherent signals.
Software: TMSC54X assembly language
Hardware: A PCI interface board is developed, including DSP, CPLD, PCI bridge, A/D converter
Publication: H. Bao, Z. Ge, J. Zhou, etc. "Digital Phase Detecting Based On Hilbert Transform and Its DSP Implementation", North-east Asia IT symposium, pp.199-203, Jan.2002 [PDF]
Nonlinear Distortion in Amplifier
Nonlinear distortion was analyzed with the notions of total harmonic distortion, intermodulation distortion and intercepting point. Simulations were done on several types of amplifiers with the EDA software - Multisim.
Hua Bao | Ph.D, Electrical Engineering
