This paper investigates the robustness of a hybrid analog/digital feedback active noise cancellation (ANC) headset system. The digital ANC systems with the filtered-x least-mean-square (FXLMS) algorithm require accurate estimation of the secondary path for the stability and convergence of the algorithm. This demands a great challenge for the ANC headset design because the secondary path may fluctuate dramatically such as when the user adjusts the position of the ear-cup. In this paper, we analytically show that adding an analog feedback loop into the digital ANC systems can effectively reduce the plant fluctuation, thus achieving a more robust system. The method for designing the analog controller is highlighted. A practical hybrid analog/digital feedback ANC headset has been built and used to conduct experiments, and the experimental results show that the hybrid headset system is more robust under large plant fluctuation, and has achieved satisfactory noise cancellation for both narrowband and broadband noises.

Stability Consideration and Implementation of a Robust Hybrid Feedback Active Noise Cancellation Headset

https://dr.ntu.edu.sg/bitstream/10356/151258/2/1-s2.0-S0360132321003322-main%20%281%29.pdf

Ten questions concerning active noise control in the built environment

This article presents the design and implementation of an active noise control (ANC) headphone system with a directional hear-through capability and compares the performance of this system to that of a standard hear-through headphone system. The directional hear-through ANC headphones are a novel integration of microphone array beamforming and ANC technologies into a pair of headphones, which provide the consumer with additional functionality and new, digitally augmented ways to interact with their acoustic environment. As the microphone array is necessarily compact, superdirective beamforming is utilised to increase its low and mid frequency directional performance. In this unique integration of two current consumer technologies, first, the ANC subsystem attempts to maximise the attenuation and then the beamformer output is added to the control signal and reproduced by the headphones’ loudspeakers, with the appropriate compensation to avoid self-cancellation. The experimental study demonstrates that the proposed spatially selective ANC headphones provide a hear-through capability in the look direction, whilst reducing ambient noise and enabling the wearer to experience reduced noise communication in a noisy environment. The proposed system thus offers the consumer the potential for an electronically enhanced acoustic experience, allowing a selective reduction in environmental noise whilst desired exterior noise remains audible.

/pdf/design-and-implementation-of-an-active-noise-control-2xvw998sb4.pdf

Design and Implementation of an Active Noise Control Headphone With Directional Hear-Through Capability

The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz and 1000 Hz was previously developed for an open window, it had limited low-frequency performance below 300 Hz, owing to the small loudspeakers used. To improve the low-frequency attenuation, four passive radiator-based speakers were affixed around the opening of a top-hung ventilation window. The active control performance between 100 Hz and 700 Hz on a single top-hung window in a full-sized mock-up apartment room was examined. Active attenuation came close to the performance of the passive insulation provided by fully closing the window for expressway traffic and motorbike passing noise types. For a jet aircraft flyby, the performance of active attenuation with the window fully opened was similar to that of passive insulation with fully closed windows. In the case of low-frequency compressor noise, active attenuation’s performance was significantly better than the passive insulation. Overall, between 8 dB and 12 dB of active attenuation was achieved directly in front of the window opening, and up to 10.5 dB of attenuation was achieved across the entire room.

Active Control of Low-Frequency Noise through a Single Top-Hung Window in a Full-Sized Room

This article presents a high-performance hardware design of block least mean square adaptive noise canceller (ANC) for in-ear headphones applications. It is based on distributed arithmetic, which stores filter partial products in look-up table (LUT). The proposed technique splits LUTs into two smaller LUTs and stores the filter partial products in offset-binary-coding form. Furthermore, the splitted LUTs are shared to compute the filter output and coefficient-increment terms. A novel strategy is also presented to update LUT contents. Compared with the best existing design, the proposed ANC for 32nd filter order requires 50% less LUT words, 5.31% less adders, 28.57% high-throughput, and relatively less critical path-delay. From the implementation results, it is found that the logic utilization of the proposed design is significantly reduced while achieving better noise cancelling performance. For example, the proposed ANC for 32nd filter order provides noise reduction of about 6–20 dB and utilizes 1.80 times less LUTs and 1.71 times less flip-flops over the best existing design.

High-Performance Hardware Design of Block LMS Adaptive Noise Canceller for In-Ear Headphones

Have you ever faced a situation where you really wanted to enjoy your favorite music in a very noisy environment? To overcome this problem, you can either block the noise or increase the music level to mask the annoying sounds. This begets the question, "Is there a better solution?" In recent years, the technology industry has grown enormously, especially in the areas of smart, mobile, and wearable electronic products. Many companies are trying to gain consumers' attention by developing high-quality products equipped with advanced noise reduction. Among them, several companies have successfully used active noise control (ANC) techniques to cope with noise problems.

Listening in a Noisy Environment: Integration of active noise control in audio products.

The disturbance picked up by error sensors may degrade the performance of narrowband active noise cancellation (NANC) systems, resulting in slow convergence of algorithm and low noise reduction. This paper proposes modified algorithms to enhance the transient and steady-state performance. A delayless filter bank is designed to separate the residual noise into parallel channels to update the corresponding adaptive filters using individual error signals. The improved performance is verified by computer simulations.

Chung-Ying Ho

Papers

Listening in a Noisy Environment: Integration of active noise control in audio products.

Individual control of narrowband noise with disturbance