Active Sound Control Research Articles

Time response of active sound control with a harmonic acoustic pneumatic source: simulations and experimental results

Active noise control is studied as a solution to reduce the blade passing frequency tonal noise of turbofans during landing and takeoff. A promising alternative to loudspeakers used as secondary sources is the Harmonic Acoustic Pneumatic Source (HAPS), that has been designed to generate a high harmonic noise level controllable in amplitude and phase using slow time varying signals. The objective is to design, characterize and optimize an active control system capable of following a time varying primary noise. A configuration with a loudspeaker acting as a primary source, a HAPS mounted laterally on a rectangular duct and an error microphone is considered. A first single-input-single-output controller for the case of plane wave control has been tested and allowed a convergence time of about 2 seconds to reach 20 dB attenuation of the acoustic pressure at 440 Hz. The results are consistent with simulations of the system and the convergence time can be explained by the dynamics of the HAPS. This study is a first step towards the objective of performing multimodal active noise control in duct with multiple sources in presence of flow.

Towards optimized nonlocal active sound control with preservation of desired sound

Towards optimized nonlocal active sound control with preservation of desired sound

An efficient technique for developing the active sound control system in electric vehicle

The sound characteristic is a critical metric to manifest the brand differentiation of electric vehicle (EV), and the sound design with more diverse acoustic characteristics has become a hot issue in current research of EV technology. In this paper, an efficient technique of active sound design (ASD) is explored to develop the control system of active sound generation (ASG) with powerful sound quality for EV. Firstly, an optimization algorithm of sound synthesis based on multi-frequency superimposition is proposed to improve the harmonic interference phenomenon in the synthesized sounds. Subsequently, an adaptive sound control strategy is formulated, where an iterative accumulation method is proposed to calculate the “virtual engine speed” of EV, and a gain table is presented to divide the running state. Besides, an ASG system is developed based on the proposed ASD technique. The tests result demonstrate that there are 18 target order sounds are reproduced perfectly, and the powerful sound quality interior EV is enhanced while the original interior acoustic environment of EV is retained, which confirms the effectiveness of the proposed control technique of ASG system. The proposed ASD technique here accelerates the change from silence to sound quality in the electric vehicles, which has important theoretical significance and engineering value.

Nonlocal active sound control for composite regions

In the active sound control problem, additional sound sources, known as control sources, are implemented at the perimeter of a protected domain. The control sources can generate secondary sound inside the shielded domain, which attenuates incoming noise. This leads to an inverse source problem. Such a problem becomes much more complicated if some desired sound is generated inside the protected area. The algorithm, known as nonlocal active sound control, successfully tackles this problem due to the projection property of the nonlocal operators involved. With the application of nonlocal control, noise generated outside the shielded domain is attenuated while the internal component of sound remains unaffected. In the present paper, the approach of nonlocal active sound control is significantly modified to be applicable to composite domains. In the test cases, three different sound propagation patterns are realized such as sound shielded from peers, free propagation, and selective sound cancelation. Numerical simulation is carried out in both frequency and time domains for broadband regimes. The results show that, even with a relatively small number of sensors and control sources, significant noise attenuation can still be achieved for a predetermined communication pattern among individual subdomains.

Research on the characteristics of EV interior sound quality and its dynamic active control system design and development un-der accelerated driving conditions.

In order to improve the interior sound quality of Electric Vehicles (EV), solve the problem of low sense of power and comfort of the interior sound as well as the large electromagnetic excitation order noise of motor and the sharp interior sound, this article designs a dynamic active sound control system for EV under accelerated driving conditions. Firstly, by comparing and analyzing the sound spectrum characteristics of fuel vehicle (FV) and EV during acceleration, a short-time Fourier transform (STFT) is adopted to extract and synthesize the engine sound. Secondly, the influence of the engine order composition and the energy distribution in the frequency domain on the sound quality of the vehicle is analyzed, and an active control system for sound quality is proposed. And the software and hardware development of the active control sound system is completed. Finally, through real-vehicle testing and verification, the sense of comfort and power of the EV interior sound has been greatly improved during acceleration, and the total value of interior sound can meet the requirement. The sound pressure level and loudness of interior sound have been increased, and the sharpness of the sound inside the vehicle has been improved, with a maximum reduction of 1.0acum.

Beyond Anti-Noise: Foundations and the Future of Active Sound Control

Beyond Anti-Noise: Foundations and the Future of Active Sound Control

Optimized nonlocal active sound control with preservation of desired sound field

In this study we implement nonlocal active sound control to shield a bounded domain from ambient noise generated outside. This technique is practically applicable even if internally generated desired sound exists. Within the protected domain, the secondary field provided by the controls located at the perimeter neutralizes the external noise while preserving the desired sound unchanged. The generality of nonlocal active sound control facilitates its real-life application since only the total acoustic field at the boundary of the protected region is required as input data. The external noise and internal desired sound are automatically separated. We investigate the optimized distributions of sensors and controls to make this method more practically realistic. A series of numerical experiments are carried out, illustrating that significant noise attenuation can be achieved even with the sparse distribution of sensors and controls if the optimized distributions are implemented. The results also demonstrate that even two controls per wavelength enable to provide essential noise attenuation with optimized distributions.

Analysis of binaural sound pressure control and virtual source characteristics in stereophonic reproduction

In stereophonic reproduction, the manipulation of relative magnitude and phase between two loudspeakers enables to create virtual sources within an azimuth region in frontal–horizontal plane. The law of sine, which is based on evaluating the interaural phase difference and a conventional method for stereophonic analysis at low frequencies, fails to explain some characteristic in stereophonic reproduction, including the influence of span angle of loudspeakers on virtual source localization and the stability of virtual source created by out-of-phase loudspeaker signals. Analogy to the method in active sound control, an alternative method for analyzing the characteristics of virtual source in stereophonic reproduction is presented in this work. On the basis of shadowless head model at low frequency, the power effort of loudspeaker signals for creating virtual source in stereophonic reproduction is evaluated. The results indicate that for frontal virtual source within the span of loudspeakers, the power effort of in-phase loudspeaker signals increases with the increase in the span angle of loudspeakers. For lateral virtual source outside the span of loudspeakers, the power effort of out-of-phase loudspeaker signals increases with the target azimuth of virtual source. Increase in power effort makes the control of binaural pressures difficulty and, thus, virtual source instable.

Development of a Sound Quality Evaluation Model Based on an Optimal Analytic Wavelet Transform and an Artificial Neural Network

The purpose of this study was to develop a sound quality model for real time active sound quality control systems. The model is based on an optimal analytic wavelet transform (OAWT) used along with a back propagation neural network (BPNN) in which the initial weights and thresholds are determined by particle swarm optimisation (PSO). In the model the input signal is decomposed into 24 critical bands to extract a feature matrix, based on energy, mean, and standard deviation indices of the sub signal scalogram obtained by OAWT. The feature matrix is fed into the neural network input to determine the psychoacoustic parameters used for sound quality evaluation. The results of the study show that the present model is in good agreement with psychoacoustic models of sound quality metrics and enables evaluation of the quality of sound at a lower computational cost than the existing models.

Research on active sound control in EV in-vehicle based on engine order sound fitting

In order to upgrade the comfort and dynamic feeling of the sound in the cabin of electric vehicle acceleration and uniform driving, this paper conducted a study on active sound making control in EVs based on sound fitting. Sound fitting was analyzed by short-time Fourier technique (STFT), sound extraction and synthesis was tested by STFT and synthesis method was conducted by Kaiser window function. A study on the sound requirements of a Class A EV was completed, in which a sound design method integrated three objective dimensions of sound amplitude strengthening, energy distribution, and order composition in the vehicle speed range, so as to determine the sound design scheme of accelerated driving with both comfort and dynamic sense. By comparing the characteristics of two kinds of engine sound extraction, the correlation between dynamic sensation and engine sound amplitude was analyzed, and the active sound parameter selection was confirmed under two conditions of acceleration and uniform speed. Efforts were devoted to conduct the active sound system program workflow diagram and system hardware design and testing, and to complete the active sound generation system (ASGS) formation and accuracy testing of the electric vehicle based on the audio system speaker, and additionally the sound calibration and target verification of the ASGS under the static conditions of the real vehicle were carried out. The objective test shows that the ASGS reduces the sharpness under the two working conditions of acceleration and constant speed to 1.0 and 0.52 acum respectively, which effectively alleviates the uncomfortable feeling brought by the high-frequency order sound, and proves that the ASGS can enhance the comfort and dynamic quality characteristics of the electric vehicle interior sound.

Selective preconditioning of an active sound control system with virtual sensing

The convergence speed of multichannel adaptive active noise control algorithms can be improved if the reference signals are preconditioned, so it is advantageous to whiten them and reduce their cross-correlations. However, this preconditioning depends on the properties of the reference signals, which will generally change over time. It may still be possible to approximate the properties of the measured reference signals using a limited number of exemplar cases. By classifying the measured reference signals into the closest of these cases, the most appropriate preconditioning can be selected for the adaptive algorithm at any one particular time. Also, one method of implementing virtual sensors is to use the additional filter method, which provides targets for the measured error signals to follow, generated from the reference signals. The performance of this virtual sensing is known to be degraded if the properties of the reference signals change, so this classification method could also be used to select the most appropriate additional filter.

Technical aspects of physical implementation of an active noise control system: challenges and opportunities

Active noise control systems have become a subject of intensive worldwide research that have aroused considerable interest as being a promising solution to the problem of low-frequency noise control. Advanced real-time signal processing technologies offer opportunities that have been adopted in many active noise control industry applications, as well as in the modern urban environment where noise reduction is gaining priority status. Depending on the application, the concept of active sound control can be implemented using different control strategies. The development and application of such systems requires in-depth knowledge and theoretical analysis in the field of digital signal processing, sensor technology, adaptive control, understanding in hardware solutions for acquisition and data processing, as well as software capabilities for modeling, visualization and control of signals. Also, the construction of such a system must give an overview of the choice and characteristics of its components in terms of the impact of the elements that make it up on its accomplishment. This paper provides an insight into the engineering aspects for implementation of an active noise control system in a duct, emphasizing all technical requirements that need to be analyzed and might further affect the systems overall performance.

Validation of a potential-based active sound control methodology

This paper describes a global active sound control methodology based on difference potentials in a three-dimensional space. The proposed alternative method allows the reduction of a boundary value problem set in a complex domain to a boundary equation. The only input data needed by the methodology are the acoustic quantities at the perimeter of the protected region. By minimizing the number of input data, the characteristics of the method provide a practical and cost-effective control system. Moreover, these quantities may pertain to the overall acoustic field composed of both the unwanted and wanted components. The most distinctive feature of this methodology is its ability to automatically differentiates between the wanted sounds and unwanted noise within targeted domains. The proposed approach requires information of neither the wanted nor unwanted component separately, but the measurements of the total field on the boundaries of the shielded domain only. This capability can be very useful for the applications related to personal audio and building acoustics as it enables protection of the predefined personal space against the noise coming from the outside. In doing so, the controls will not interfere with the detectors' recognition of the wanted sound or communication among speakers in the room.

Active sound quality control of vehicle interior noise using a dual sampling-rate active noise equalization algorithm

In-vehicle active sound quality control (ASQC) system is an advanced application of active noise control (ANC) technology, which always suppresses the interior sound pressure or improves the psychoacoustic features. However, the connection between the sound quality control state and the vehicle's working state is normally ignored, and the passenger's sound perception typically expects a linear relationship between the vehicle speed and sound loudness. This paper presents a dual sampling-rate active noise equalization algorithm. The low sampling-rate signal is used to improve system computing efficiency, the high sampling-rate signal is used to improve the ASQC effect, and their conversion communication uses a hold (low to high) and a sampler (high to low). The data relating to the ASQC system was collected, and some sound quality evaluations were conducted for determining two appropriate sampling-rate values. Combining a genetic algorithm and the corresponding ASQC simulation system, the algorithmic optimal convergence coefficients and gain coefficients were further determined at different engine speeds. The verification results of ASQC using this proposed algorithm show that the loudness of interior noise is effectively suppressed; the nonlinear index is reduced to 1.37, improving by 37% relative to the original noise and by 20% compared to the ANC system.

Three-dimensional characterization of spatial sound fields via acousto-optic sensing

Characterizing audible sound fields over space is at the core of many applications in acoustics and audio technology, including active sound field control, spatial audio, and the experimental analysis of sound radiation. For this purpose, arrays of microphones are commonly deployed across the sound field, with an inter-microphone spacing that depends on the highest frequency studied. Capturing sound fields at mid and high frequencies is nonetheless challenging, as the number of transducers required becomes impractically large and the scattering of sound introduced by the array is often significant. Acousto-optic sensing enables the remote and non-invasive characterization of acoustic fields, and thus it represents an attractive alternative to conventional electro-mechanical transducers in several applications. The phase-shift that laser beams experience as they travel through a pressure field are measured via optical interferometry. The optical measurements are then used to reconstruct the field that originated such phase variations. In this study, we project the measured data into a set of functions suitable to represent sound fields over space. The projection makes it possible to improve the reconstruction accuracy and extrapolate the reconstruction outside the measured region. We demonstrate the method by reconstructing the three-dimensional sound field inside a room using optical data.

Sound Quality Control Based on CEEMD Blind Source Separation and FELMS Algorithm

The reduction in sound pressure level is the focus of noise reduction in construction machinery, but the sound quality parameters can better describe the operator’s subjective perception of noise. This paper proposes a sound quality control method for the cab, which is based on complementary ensemble empirical mode decomposition for signal decomposition and reconstruction and an adaptive control algorithm error filter. Firstly, a subjective and objective prediction model was created to identify the target parameters for the sound quality control in the cab. Secondly, the noise was reconstructed based on a complementary ensemble empirical mode decomposition method, thus evaluating the influence of each component on the sound quality and determining the frequency interval. Lastly, the active sound quality control was completed based on the variable step size filter-error least mean square algorithm. The experiments were performed in the cab of a mini-excavator to verify the method’s effectiveness. It was verified that the loudness peak drops by 0.95 sones under stationary idle working conditions. The results demonstrate that the above methods play a guiding role in the actual application of sound quality control for the cab of construction machinery.

A computationally efficient active sound quality control algorithm using local secondary-path estimation for vehicle interior noise

Current active noise equalization or active sound profiling algorithms with a parallel structure are typically used for sound quality improvement of multi-harmonic noise. The computational efficiency and system performance may, however, be severely degraded due to an increase in the length of estimated secondary path or the number of controlled frequencies. To alleviate this problem, a local secondary path estimation and filtered-error structure based active sound quality control (LFE-ASQC) algorithm is proposed in this paper. The algorithm utilizes a set of low-order local secondary path (LSP) models to perform filtering operations and uses the filtered pseudo-error signals instead of usual filtered reference signals to update control filter weights, thus it not only has good spectral reshaping capability but also requires notably low computational effort. Two new LSP modeling methods are also proposed. Moreover, a computational complexity analysis of the proposed LFE-ASQC algorithm is provided. Numerical simulations are conducted to evaluate the accuracy of the LSP modeling methods and the performance of the LFE-ASQC algorithm. In addition, the powerful sound quality of a real vehicle interior noise during acceleration is designed and realized. Experimental results demonstrate that the proposed algorithm achieves satisfactory active sound quality control for stationary and non-stationary multi-tonal noises.

Optimized nonlocal active sound control in frequency domain

In the active sound control problem considered in the paper, a quite arbitrary closed region is acoustically shielded from ambient noise generated outside via implementation of secondary sound sources which are situated at the perimeter of the domain to be protected. It is presumed that the information available for the operation of control is only limited by the acoustic field that can be measured on a closed surface around the shielded region. The problem becomes much more complicated if there are desired sound sources situated inside the shielded region. In this case the input field is determined by contributions from noise, desired sound and controls. It is supposed that only the total acoustic field is available that makes the statement of the problem quite general and realistic. As the output, it is required to attenuate noise while preserving the desired field unaffected. To tackle the problem, a recently developed algorithm based on the nonlocal control is applied. From the point of view of a practical realization, the number of microphones and loudspeakers should be minimized. We propose for the first time some ways to essentially optimize distribution patterns of controls and sensors for the nonlocal control with preservation of desired sound. Numerical experiments are carried out for noise attenuation in a cube to study the trade-off between the level of noise reduction and number of sensors and controls. It is demonstrated that the nonlocal control can be efficiently realized with a reasonable number of sensors and controls. As shown, with only two controls per wavelength the achieved level of noise attenuation exceeds 10 dB. This result matches the optimal local control when any desired sound is absent.

Hybrid vibro-acoustic active control method for vehicle interior sound quality under high-speed

For the problem of active noise control (ANC) and active vibration control (AVC) methods, only noise and vibration can be controlled separately. Active sound quality control (ASQC) method and AVC method are combined to carry out an in-depth study on the active control method of vehicle interior sound quality, using the vibration-sound transfer function and considering the requirements of sound quality. Combined with the adaptive noise equalizer (ANE) algorithm, a sound retention factor was introduced on the basis of the hybrid vibro-acoustic filter-u and filter-x least mean square (HVA-FUXLMS) algorithm, a hybrid vibro-acoustic adaptive noise equalizer (HVA-ANE) algorithm was proposed to control the sound quality. Based on the filter-error least mean square algorithm (FELMS) algorithm, a hybrid vibro-acoustic empirical-mode-decomposition frequency-domain block filter-error least mean square (HVA-EMDFELMS) algorithm for vehicle interior sound quality was proposed. Vibration and noise at high speeds are collected and analyzed for sound quality levels. This article used HVA-ANE and HVA-EMDFELMS algorithms to perform ASQC simulation experiments. The results showed that the noise loudness was greatly reduced while the noise and vibration control was taken into account by the HVA-ANE algorithm and HVA-EMDFELMS algorithm. Hybrid vibro-acoustic active control method for vehicle interior sound quality can effectively improve the sound quality of vehicle and can be applied to the active control of vehicle noise and related engineering noise.

A fast analytical framework to identify acoustic field properties of rectangular enclosures with a vibrating plate

In this study, to estimate the acoustic field properties inside a cavity with a flexible plate, a fast analytical framework based on the modal interaction approach in frequency domain is introduced. In order to elicit such an algorithm, an in-depth investigation on self-cancellation and mode coupling phenomena is presented to show how to determine effective vibrational and acoustic modes in the acoustic-structure interaction problem. The outline of this method is a compromising between accuracy and computational cost. Unlike methods require high computational cost such as FEM and BEM, the present method is suitable to obtain a rapid acoustic field estimation which is applicable for optimization problems as well as the design of active sound control systems. The results are validated with the experimental measurements available in literature and FEM solutions.