Marek Pawelczyk

Active Noise Control

This paper deals with an alternative modal active control approach to reduce sound transmission through a structure excited by an acoustic wave. Active control makes it possible to conserve lightness
while improving acoustic performances. &#8220;Modal mass damping control&#8221; is proposed for light and small
structures having slight modal overlap. The aim of this control is to modify the modal distribution of high
radiation efficiency modes with active modal virtual mass and active modal damping. The active virtual
mass effects lower eigen frequencies to less audible frequency range while reducing vibration amplitudes
in a broad frequency range. An application of this concept is presented in a simple smart structure. It
is harmonically excited on large bandwidth by a normal acoustic plane wave. Results obtained by active
modal virtual mass and damping control are compared to other modal control approaches.

V. Lhuillier

L. Gaudiller

C. Pezerat

S. Chesne

Improvement of Transmission Loss Using Active Control with Virtual Modal Mass

One of the problems concerned with active noise control is the existence of acoustical feedback between the control value (&#8220;active&#8221; loudspeaker output) and the reference signal. Various experiments show that such feedback can seriously decrease effects of attenuation or even make the whole ANC system unstable. This paper presents a detailed analysis of one of possible approaches allowing to deal 
with acoustical feedback, namely, virtual unidirectional sound source. With this method, <i>two</i> 
loudspeakers are used together with control algorithm assuring that  the combined behaviour of the pair makes virtual propagation of sound only in one direction. Two different designs are presented 
for the  application of active noise control in an acoustic duct: analytical (leading to fixed controller) and adaptive. The algorithm effectiveness in simulations and real experiments for both solutions is showed, discussed, and compared.

Dariusz Bismor

Optimal and Adaptive Virtual Unidirectional Sound Source in 
                        Active Noise Control

The paper presents an active sound intensity probe that can be used for sound source localization in standing wave fields. The probe consists of a sound hard tube that is terminated by a loudspeaker and an integrated pair of microphones. The microphones are used to decompose the standing wave field inside the tube into its incident and reflected part. The latter is cancelled by an adaptive controller that calculates proper driving signals for the loudspeaker. If the open end of the actively controlled tube is placed close to a vibrating surface, the radiated sound intensity can be determined by measuring the cross spectral density between the two microphones. A one-dimensional free field can be realized effectively, as first experiments performed on a simplified test bed have shown. Further tests proved that a prototype of the novel sound intensity probe can be calibrated.

Thomas Kletschkowski

Delf Sachau

Design and Calibration Tests of an Active Sound Intensity Probe

The FXLMS algorithm, used extensively in active noise control (ANC), exhibits frequency-dependent convergence behavior. This leads to degraded performance for time-varying tonal noise and noise with multiple stationary tones. Previous work by the authors proposed the eigenvalue equalization filtered-x least mean squares (EE-FXLMS) algorithm. For that algorithm, magnitude coefficients of the secondary path transfer function are modified to decrease variation in the eigenvalues of the filtered-x autocorrelation matrix, while preserving the phase, giving faster convergence and increasing overall attenuation. This paper revisits the EE-FXLMS algorithm, using a genetic algorithm to find magnitude coefficients that give the least variation in eigenvalues. This method overcomes some of the problems with implementing the EE-FXLMS algorithm arising from finite resolution of sampled systems. Experimental control results using the original secondary path model, and a modified secondary path model for both the previous implementation of EE-FXLMS and the genetic algorithm implementation are compared.

Stephan P. Lovstedt

Jared K. Thomas

Scott D. Sommerfeldt

Jonathan D. Blotter

Genetic Algorithm Applied to the Eigenvalue Equalization Filtered-x LMS Algorithm (EE-FXLMS)

With the advancement of digital signal processing technologies, consumers are more concerned with the quality of multimedia entertainment in automobiles. In order to meet this demand, an audio enhancement system is needed to improve bass reproduction and cancel engine noise in the cabins. This paper presents an integrated active noise control system that is based on frequency-sampling filters to track and extract the bass information from the audio signal, and a multifrequency active noise equalizer to tune the low-frequency engine harmonics to enhance the bass reproduction. In the noise cancellation mode, a maximum of 3&#x2009;dB bass enhancement can be achieved with significant noise suppression, while higher bass enhancement can be achieved in the bass enhance mode. The results show that the proposed system is effective for solving both the bass audio reproduction and the noise control problems in automobile cabins.

Liang Wang

Woon Seng Gan

Sen M. Kuo

Integration of Bass Enhancement and Active Noise Control System in Automobile Cabin

We deal with the design of active noise control systems for ventilation ducts with a pair of loud-speakers based on sampled-data <svg style="vertical-align:-3.13504pt;width:26.4625px;" id="M2" height="14.775" version="1.1" viewBox="0 0 26.4625 14.775" width="26.4625"  xmlns="http://www.w3.org/2000/svg">
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				<tspan style="font-size: 8.75px; " x="0" y="0">∞</tspan>
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</svg> optimization, in order to improve our previous study with a single loudspeaker. The resultant controller requires lower computational complexity for the implementation,  compared to the standard time-varying adaptive controllers, since it is time-invariant and the order is comparable. Moreover, the effect of Swinbanks' source is automatically recovered by the <svg style="vertical-align:-3.13504pt;width:26.4625px;" id="M3" height="14.775" version="1.1" viewBox="0 0 26.4625 14.775" width="26.4625"  xmlns="http://www.w3.org/2000/svg">
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				<tspan style="font-size: 8.75px; " x="0" y="0">∞</tspan>
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</svg> optimization. The benefit of the proposed method is also confirmed from experimental results for a real house, where the achieved noise attenuation level is about twice as much as that of the single loudspeaker case.

Yasuhide Kobayashi

Hisaya Fujioka

Active Noise Cancellation for Ventilation Ducts Using a Pair of Loudspeakers by Sampled-Data <svg style="vertical-align:-3.3907pt" height="16.025" version="1.1" viewBox="0 0 29.8375 16.025" width="29.8375" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,11.737)"><path id="x210B" d="M702 678l12 -14l-18 -14q-124 -96 -232 -310q25 10 62 21l53 18l33 43q101 126 187 195q88 70 135 70q57 0 57 -50q0 -78 -98 -145q-86 -58 -206 -105q-174 -251 -174 -334q0 -15 9.5 -25t24.5 -10q55 0 167 129l21 -13q-120 -146 -202 -146q-39 0 -63 24t-24 65&#xA;q0 101 104 262l-107 -41q-56 -110 -132 -193q-75 -82 -145 -109q-31 -11 -56 -11t-41 16.5t-16 43.5q0 129 283 247q17 29 20 33l22 36q1 2 9 13.5l14 20.5q18 28 59 77q34 39 87 86q-5 -1 -20 -1q-44 0 -124 44q-62 34 -102 34q-48 0 -82 -31q-34 -30 -34 -70q0 -44 22 -69&#xA;t66 -25q37 0 65 20.5t56 65.5l18 -9q-54 -107 -141 -107q-59 0 -93 34.5t-34 91.5q0 58 50 105q49 46 125 46q28 0 58 -11q35 -13 84 -38q59 -31 86 -31q42 0 80 19q16 9 42 28zM958 635q0 22 -24 22q-28 0 -86 -63q-56 -60 -128 -160q238 105 238 201zM307 241&#xA;q-110 -50 -165.5 -98t-55.5 -99q0 -24 24 -29q67 0 197 226z" /></g><g transform="matrix(.012,-0,0,-.012,17.012,15.825)"><path id="x221E" d="M983 225q0 -112 -67 -174.5t-150 -62.5q-91 0 -154.5 43.5t-113.5 129.5q-49 -85 -104 -129t-138 -44q-98 0 -158.5 66t-60.5 154q0 59 21 106.5t54.5 75.5t70.5 43t73 15q90 0 152.5 -43.5t112.5 -128.5q48 84 104.5 128t140.5 44q93 0 155 -65t62 -158zM478 196&#xA;q-27 49 -47 80t-50 67t-64 54t-73 18q-48 0 -81.5 -47t-33.5 -128q0 -96 37.5 -157.5t99.5 -61.5q68 0 117.5 47t94.5 128zM889 204q0 91 -35.5 151t-99.5 60q-68 0 -119 -47t-95 -127q27 -49 47 -80.5t50 -67.5t65 -54t74 -18q113 0 113 183z" /></g></svg> Optimization

Excessive noise in neonatal care units and inside incubators can have a number of detrimental effects on an infant&#39;s health. We proposed a novel, audio-integrated approach to achieve active noise control (ANC) for infant incubators. We also presented the implementation of the robust, nonlinear filtered-X least mean M-estimate algorithm, for reducing impulsive interference in incubators. The healthcare application is further enhanced by integrating the &#8220;womb
effect&#8221;, that is, by using intrauterine and maternal heart sounds, proven to be beneficial to infant health, for soothing the infant and masking the residual noise. A computer model for audio-integrated noise cancellation utilizing experimentally measured transfer functions is developed for simulations using real medical equipment noise. The simulation of the audio integrated ANC system produced optimal results and the system was further validated by real-time experiments to be robust and efficient.

Lichuan Liu

Shruthi Gujjula

Priya Thanigai

Still in Womb: Intrauterine Acoustic Embedded Active Noise Control for Infant Incubators

An active noise control (ANC) system is model dependent/independent if its controller transfer function is dependent/independent on initial estimates of path models in a sound field. Since parameters of path models in a sound field will change when boundary conditions of the sound field change, model-independent ANC systems (MIANC) are able to tolerate variations of boundary conditions in sound fields and more reliable than model-dependent counterparts. A possible way to implement MIANC systems is online path modeling. Many such systems require invasive probing signals (persistent excitations) to obtain accurate estimates of path models. In this study, a noninvasive MIANC system is proposed. It uses online path estimates to cancel feedback, recover reference signal, and optimize a stable controller in the minimum 
                  H<sub>2</sub> norm sense, without any forms of persistent excitations. Theoretical analysis and experimental results are presented to demonstrate the stable control performance of the proposed system.

Jing Yuan

Noninvasive Model Independent Noise Control  with Adaptive Feedback Cancellation

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Advances in Acoustics and Vibration

Active Noise Control

Active Noise Control

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