Woon S. Gan

An integrated audio and active noise control headset

This paper presents an integrated approach in designing a noise reduction headset for audio and communication applications. Conventional passive headsets give good attenuation of ambient noise in the upper frequency range, while most of these devices fail below 500 Hz. Unlike the feedforward method, the adaptive feedback active noise control technique provides more accurate noise cancellation since the microphone is placed inside the ear-cup of the headset. Furthermore, the system uses a single microphone per ear cup, thus producing a more compact, lower power consumption, cheaper solution and ease of integration with existing audio and communication devices to form an integrated feedback active noise control headset. Simulation results have been conducted to show that the integrated approach can remove the disturbing noise and, at the same time, allow the desired speech or audio signal to pass through without cancellation.

Adaptive feedback active noise control headset: implementation, evaluation and its extensions

In this paper, we present design and real-time implementation of a single-channel adaptive feedback active noise control (AFANC) headset for audio and communication applications. Several important design and implementation considerations, such as the ideal position of error microphone, training signal used, selection of adaptive algorithms and structures will be addressed in this paper. Real-time measurements and comparisons are also carried out with the latest commercial headset to evaluate its performance. In addition, several new extensions to the AFANC headset are described and evaluated.

Applications of adaptive feedback active noise control system

This paper presents the experimental results of using the single-channel adaptive feedback active noise control (AFANC) algorithm with an innovative setup to achieve global attenuation of industrial machine noise in settings such as large manufacturing plants. An effective solution of using active/passive techniques and three distributed error sensors is proposed. The performance of the AFANC algorithm is verified by real-time experiments using the TMS320C32 DSP to control vibratory bowl and welding power generator noises. The experiments results show that this single-channel AFANC system can effectively reduce the noise level and is cost effective, portable, and easy for installation to control many noisy sources in large spaces.

Virtual bass for home entertainment, multimedia PC, game station and portable audio systems

In digital audio playback systems for home entertainment, multimedia PC, game station and portable audio devices, there is a strong demand to produce deep bass using small multimedia speakers and earphones, without the need for additional subwoofer or expensive speakers/earphones. This paper describes a technique in synthesizing psycho-acoustic bass over a pair of stereo speakers using the pitch perception theory. This new method of creating a bass effect for the musical signal has been found to be very effective and simple in implementation, without increasing significant cost in many modern digital audio systems. A subjective evaluation is also being performed to validate the virtual bass implementation.

Nonlinear least-square solution to flat-top pattern synthesis using arbitrary linear array

This paper presents a new approach for synthesizing flat-top patterns, based on the least-square error criterion. The cost function is formulated according to the amplitude approximation error without phase constraint. The optimal array weight is obtained by using the Levenberg-Marquardt nonlinear optimization algorithm. Simulations are performed to compare the proposed approach with the Woodward-Lawson method and two recent methods using minimax and adaptive array techniques, respectively. The results indicate that the approach is effective in sidelobe control and synthesizing prespecified patterns for arbitrary linear arrays.

Adaptive filtering using constrained subband updates

This paper describes and analyzes a class of subband adaptive filters (SAF) that stems from various approaches of applying subband and multirate techniques in adaptive filtering. This class of SAF has a unique structure of weight-control mechanism where subband error signals are used to actuate the adaptation of a fullband weight vector. In this paper, we show that the recursive weight adaptation can be expressed as an underdetermined least-squares solution. Within this deterministic framework, we show its underlying affinity with the normalized least-mean-square (NLMS) and affine projection (AP) algorithms. We then compare the efficacy of these algorithms in terms of convergence rate and computational complexity.

Integrated near-end acoustic echo and noise reduction systems

This paper presents the development of integrated near-end acoustic echo and noise reduction algorithm. The modified frequency-sampling filter (FSF) provides an effective filterbank for splitting the signal into equally spaced frequency channels. The center clipper and attenuator are employed at each frequency bin for attenuating near-end acoustic echo and noise. The adaptive clipping threshold and dynamic attenuator value are updated based on the optimized voice-activity detector (VAD). Computer simulations using speech and measured room impulse response show that the near-end acoustic echo and noise are suppressed successfully.

Active noise control for motorcycle helmets

Continuous exposure to high-level of motorcycle noise has a risk of damaging hearing and degrading the quality of music for entertainment. This paper develops an innovative audio-integrated active noise control (ANC) system for motorcycle helmets to cancel noise and preserve the audio quality. Motorcycle noises measured at different speeds are recorded, analyzed and used to evaluate the performance of audio-integrated ANC system. Both computer simulations and real-time experiments show the feasibility of using the developed ANC helmets for hearing protection and audio entertainment.

Digital signal processor architectures and programming

This paper presents modern digital signal processor architectures including multiply-accumulate unit, shifter, pipelining and parallelism, buses, data address generators, and special addressing modes and instructions. In addition, the most effective mixed C and assembly programming technique is suggested for software development

On a class of subband adaptive filters with inherent decorrelating properties

This paper describes and analyzes a class of subband adaptive filters (SAFs) that stems from various approaches of applying subband and multirate techniques in adaptive filtering. This class of SAFs has a unique weight-control mechanism, whereby subband error signals are used to adapt a fullband tap-weight vector. In this paper, we show that the recursive tap-weight adaptation can be expressed as an optimization process which approximates the steepest-descent and Newtons methods in minimizing two fundamentally different error criteria. Theoretical analysis reveals the inherent decorrelating properties of the adaptive algorithm, which manifest themselves in different forms as integral elements of the weight-control mechanism.