Active Sound Control Research Articles

An experimental investigation of two module configurations for use in active segmented partitions

Individual modules intended for active segmented partitions should be carefully analyzed before they are advanced as viable tools for active sound transmission control. In this paper we present experimental evaluations of two vibration-controlled modules: a single-composite-leaf (SCL) configuration and a double-composite-leaf (DCL) configuration. Experimental apparatuses and procedures are introduced to assess their normal-incidence transmission losses over a bandwidth from 40 to 1970 Hz. The average transmission loss of the passive SCL module is found to be 21 dB. If its transmitting diaphragm acceleration is minimized through active control, transmission loss increases somewhat at lower frequencies but decreases at higher frequencies, producing no increase in the average value. The average transmission loss of the passive DCL module is found to be 43 dB. After its transmitting diaphragm acceleration is actively minimized, the transmission loss increases substantially at all frequencies (especially at low frequencies), to produce an average value of 77 dB. Thus, while both configurations have the same underlying control objective, the DCL module yields a 56 dB average improvement over the SCL module through simple configurational changes. An alternative control scheme is investigated that minimizes acoustic pressure in the DCL module cavity, but it is found to be less effective.

Engineering applications of active sound and vibration control

Engineering applications are the natural milestones where new technologies have to proof their potential and their perspectives. For active control of sound and vibration, this applicative justification was given in terms of specialised solutions for specific applications rather than as solution for widespread applications of large production number. This is in contrast to multiple expectations and promises and reflects the persistent disadvantage of unviable implementation efforts. Thus, besides ongoing research progress, further and sustainable development and implementation work of some specialised engineering groups has helped to keep this hardly youthful approach attractive and promising. The paper reflects the applicative state of the art of active sound and vibration control and gives further evidence by three case studies for fully developed and practically applied engineering solutions. These case studies refer to the suppression of two self-excited sound field oscillations, wind-tunnel buffeting and combustion instabilities, and to active sound design, a way of extending the focus of sound field control to arbitrary target sounds in order to provide a flexible tool for in situ sound tests in the original environmental context. From such applications it can be expected that further improvements for all components involved including sensors and actuators will help to extend the applicative basis of active sound and vibration control.

Active Sound and Vibration Control

Active Sound and Vibration Control

Active Sound and Vibration Control: Theory and Applications [Book Review

Active Sound and Vibration Control: Theory and Applications [Book Review

In-room sound reproduction using active control: Simulations in the frequency domain and comparison with wave field synthesis

Active sound control simulations were performed for progressive sound field reproduction over a ‘‘large’’ area using multiple monopole loudspeakers. The model is limited to the simulation of the acoustical output of the prescribed loudspeaker array in a simple room, and is based on achieving an optimal control in the frequency domain. This rather simple approach is chosen for this first feasibility study concerning a limited number of possible configurations of sensing microphones and loudspeakers. Other issues of interest concern the comparison with wave field synthesis, the control mechanisms and transducer configurations. As it is demonstrated, in-room reproduction of sound field using active control can be achieved with a residual normalized squared error below 2% while open-loop wave field synthesis gives more than 100% of error in the same situation. Usage of active control technique suggests the possibility to automatically overcome the room’s natural dynamics. A special surrounding configuration of sensors is introduced for a sensor-free listening area. [Work supported by NSERC, NATEQ, VRQ, and Université de Sherbrooke.]

Experimental energetic analyses of an actively controlled one-dimensional acoustic waveguide

Technological development has made it possible to implement digital active noise control systems in real time. This work compares the performance of different adaptive control methods applied to a one-dimensional waveguide. The compared control methods are the frequency-domain filtered-X LMS using potential energy density and kinetic energy density as cost functions, and the active sound intensity control (ASIC), which uses active intensity as the cost function. The ASIC controller is implemented with both the P–U approach (measuring pressure and particle velocity at the same time) and the P–P approach (using two microphones to estimate the active intensity). The waveguide is a circular PVC duct with a primary source placed at one end, the secondary source placed near the mid-span of the duct, and with an open-ended termination. The analyses were performed comparing the results in terms of the potential energy density, the active intensity, and the acoustic power radiated by the sources. Moreover, it is shown how to choose suitable error sensors and their influence in the performance of the ASIC controller. The results show that the control methods achieved the same final result and, as expected, when the volume velocity of the secondary source was driven to the optimal volume velocity, the primary source and the secondary source radiated less acoustic power than the uncontrolled primary source. Besides, the sound intensity was effectively attenuated throughout the duct.

Finite Element Methods in Local Active Control of Sound

The active control of sound is analyzed in the framework of the mathematical theory of optimal control. After setting the problem in the frequency domain, we deal with the state equation, which is a Helmholtz partial differential equation. We show the existence of a unique solution and analyze a finite element approximation when the source term is a Dirac delta measure. Two optimization problems are successively considered. The first one concerns the choice of phases and amplitudes of the actuators to minimize the noise at the sensors' location. The second one consists of determining the optimal actuators' placement. Both problems are then numerically solved. Error estimates are settled and numerical results for some tests are reported.

外部入射騒音の3次元空間における能動的音響制御(音響計測)

外部入射騒音の3次元空間における能動的音響制御(音響計測)

319 鉄道車輪/レール系騒音の車上設置型デバイスによるアクティブ消音制御の基礎的研究(能動的騒音制御,OS-20:サイレント工学)

The concept of the active sound cancellation control of the railway wheel/rail noises by the On-vehicle-type devices is presented. And the apparatus of randomly exciting 60kg rail by the electromagnetic shaker which is enclosed with the panel system simulating the floor/side wall of the railway car was constructed. Further, one unit of the devices which realizes in principle the sound cancellation control of the see-through space was manufactured and the parabola-microphone and actuating speaker was installed on it in addition to the controller consisting of the analog electrical band-pass filter circuit group. And it was verified that the sound cancellation control effects are observed actually for the both cases of a speaker and the randomly excited rail system which were regarded as the primary sound sources.

A planar active sound control system using two-dimensional spatial harmonics

An active sound control system based on the extraction of orthogonal spatial harmonics is considered. The system comprises two parallel planar rectangular receiving arrays consisting of small monopole receivers and two planar rectangular transmitting arrays (installed parallel to the receiving arrays) consisting of small monopole transmitters. The field received by the receiving arrays is approximated by a finite number of propagating plane waves with the help of the Fourier transform. The transmitting arrays excite the same set of plane waves outside the system, their amplitudes being chosen so as to cancel the incident external field in a certain region near the system behind the transmitting arrays. The performance of the system is considered for both continuous and discrete distributions of transmitters and receivers. Allowance is made for random errors in the transmitters and receivers, individual to each device.

Research in the field of active sound transmission control

Sound transmission through an unperforated partition may be described as the vibro-acoustic process in which fluid-borne sound waves incident upon the partition from the source side force it to vibrate and consequently radiate transmitted fluid-borne sound waves into the space on the opposite (receiving) side. Active reduction of sound transmission through partitions, or active sound transmission control (ASTC), denotes an active modification to this process. It may be defined as the reduction of transmitted sound through the action of electro-mechano-acoustical devices regulating any or all stages of the vibro-acoustic sound transmission process. In certain analyses, this branch of active noise control has referred to situations in which electro-mechanical actuation is applied only to a partition through which sound is transmitting. However, since ASTC may be achieved by other means, and since much research in the field has utilized other techniques, this limitation is clearly too restrictive. This paper reviews and categorizes many research efforts in the field, and provides a brief history of the efforts based on an extensive bibliography of the subject matter. It also identifies research areas that could be pursued in the future.

Vibration-controlled modules for use in active segmented partitions

Active segmented partitions (ASPs) have become an important topic in the research of active sound transmission control (ASTC). Many ASTC applications require lightweight partitions, high transmission loss over a broad frequency range, and applicability to a variety of source and receiving space conditions. This paper provides theoretical, numerical, and experimental evaluations of specific ASP module configurations used to satisfy these requirements. The control objective for each is to induce global vibration control of its various transmitting surfaces through direct minimization of the normal vibration of its principal transmitting surface. Normal-incidence transmission loss estimates are based on equivalent circuit analysis and corresponding experimental measurements are made using plane wave tube techniques. The paper explains why characteristic single diaphragm configurations are unable to use this strategy effectively. It also discusses two dual diaphragm configurations that use the control scheme particularly well to produce efficient global control of their transmitting surfaces and achieve very high transmission loss over a broad frequency range. The designs facilitate incorporation into full ASP arrays and satisfy other useful criteria.

Active Noise Control of the Exhaust Low Frequency Sound from the Ship with the Diesel Engines

Active Noise Control of the Exhaust Low Frequency Sound from the Ship with the Diesel Engines

Impacts of structural–acoustic coupling on the performance of energy density-based active sound transmission control

This paper investigates numerically the performance of the active sound transmission control into a rectangular cavity through a flexible panel under the energy density-based error-sensing algorithm. Full coupling between the sound transmitting panel and the enclosed space is considered. A pure vibration actuator, a pure acoustic source and a combined control source system are used as the secondary control source in the active control and their performances are studied. Formulae for the coupled eigenfrequencies of the cavity and the flexible panel are also derived. The strength of the structural–acoustic coupling, the ratio between the first eigenfrequencies of the cavity and the panel and the difference between the excitation frequency and the coupled eigenfrequencies, especially the latter, are found to have crucial impacts on the performance of the active control regardless the type of control source used.

The virtual microphone technique in active sound field control systems

Active Sound Field Control (AFC) has been proven very useful in reverberation enhancement applications in large rooms. However, feedback control is required in order to eliminate peaks in the frequency response of the system. The present research closely follows the studies of Shimizu in AFC, in which smoothing of the rooms transfer function is achieved by averaging the impulse responses of multiple microphones. ‘‘The virtual or rotating microphone technique’’ reduces the number of microphones in the aforementioned AFC technology, while still achieving the same acoustical effects in the room. After the impulse responses at previously specified pairs of microphone positions are measured, the ratio of transfer functions for every pair is calculated, thus yielding a constant K. Next, microphones are removed and their impulse responses are reproduced by processing the incoming signal of each pair through a convolver, where the computed K constants have been previously stored. Band limiting, windowing and time variance effects are critical factors, in order to reduce incoherence effects and yield reliable approximations of inverse filters and consequently calculations of K. The project is implemented in a church lacking low frequency reverberation for music and makes use of 2 physical and 2 virtual microphones.

Active minimization of acoustic potential energy in a two-dimensional multimode waveguide

The nonlinear inverse problem of active sound control in a two-dimensional waveguide is addressed. To solve the problem, a numerical algorithm based on an exhaustive search for coordinates of the desired sources over a curvilinear mesh and on the regularized quadratic algorithm for minimization with respect to their intensities is proposed. Numerical results for circular and elliptical antenna arrays are discussed.

107 モード制御と適応制御の併用による 3 次元空間の能動的音響制御

107 モード制御と適応制御の併用による 3 次元空間の能動的音響制御

Model-free frequency domain iterative active sound and vibration control

In this paper, a model-free iterative feedback tuning method is presented to tune a frequency domain controller for a set of narrow-band disturbances. A single control problem with multiple tones of the disturbance is split into a set of parallel control problems. Due to the representation in the frequency domain, there are only control amplitude and phase to be tuned for each tone. Tuning is performed through a sequence of experiments which enables the calculation of a model-free gradient of a quadratic cost function. The number of experiments at each iterative step is R× S+1, where R is the number of controls signals and S is the number of output signals. Results on a laboratory active sound control system are shown. The example demonstrates the practical effectiveness of the method.

Active control of sound arounda fluid-loaded plate using multiple piezoelectric elements

This paper presents a method of using a least-squaresapproach and tabu search technique together with the commerciallyavailable FEA code, ANSYS, for active sound control around afluid-loaded plate by multiple piezoelectric elements.A numerical model of FEA is used to construct the transferfunction matrices, which relate the primary (an acousticsource) and the secondary (piezoelectric elements) sources tothe acoustic pressures in the field of interest withconsideration of environmental effects. With the transfer function matrices, the least-squares algorithm and tabu searchtechnique are applied for subsequent active sound control. Thispaper shows how to implement the local and global active soundcontrol in the upper and lower half-spaces of the plate by the useof multiple piezoelectric elements through some case studies.

904 外部入射騒音の 3 次元空間における能動的音響制御

904 外部入射騒音の 3 次元空間における能動的音響制御