Directivity-Based Passive Barrier for Local Control of Low-Frequency Noise
19 Dec 2018-Vol. 26, Iss: 04, pp 1850012
TL;DR: In this article, the authors proposed a novel concept of local mitigation of the transmitted transmission loss offered by a noise barrier separating two acoustic spaces in the low-frequency range, which can improve the transmission loss.
Abstract: This work concerns with improving the transmission loss offered by a noise barrier separating two acoustic spaces in the low-frequency range. A novel concept of local mitigation of the transmitted ...
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TL;DR: In this paper , an analytical solution to the sound radiation behavior of vibrating thin mode localized Al/Al2O3 functionally graded plates (FGM) with varying boundary conditions utilizing its physical neutral surface through analysis and simulation was investigated.
5 citations
01 Oct 1986
TL;DR: In this paper, the potential effectiveness of tuned Helmholtz resonators connected to the partition cavity is investigated as a method of improving transmission loss, which is demonstrated by a simple theoretical model and then experimentally verified.
Abstract: Double-leaf partitions are often utilized in situations requiring low weight structures with high transmission loss, an example of current interest being the fuselage walls of propeller-driven aircraft. In this case, acoustic excitation is periodic and, if one of the frequencies of excitation lies in the region of the fundamental mass-air-mass frequency of the partition, insulation performance is considerably less than desired. The potential effectiveness of tuned Helmholtz resonators connected to the partition cavity is investigated as a method of improving transmission loss. This is demonstrated by a simple theoretical model and then experimentally verified. Results show that substantial improvements may be obtained at and around the mass-air-mass frequency for a total resonator volume 15% of the cavity volume.
5 citations
TL;DR: A novel semi-active actuator with tunable mass moment of inertia that can enhance the transmission loss of a noise barrier for time-varying narrow-band noise by more than 10 dB in targeted frequency bands is proposed.
3 citations
TL;DR: In this article , an adaptive tuned mass inertance damper (ATMID) is proposed for structural vibration control, which can produce an alterable inertance, which gives rise to seamless variability in device frequency; consequently, the device frequency can be tuned to that of the excitation.
Abstract: In this paper, an inerter-based device for structural vibration control is proposed with which inertance can be altered relying on the frequency changes of the excitation. In this manner, a tuned mass damper is developed in such a way that it is assembled with a ball-screw inerter along with a new continuously variable transmission system. The device is termed an adaptive tuned mass inertance damper (ATMID). The ATMID is able to produce an alterable inertance, which gives rise to seamless variability in device frequency; consequently, the device frequency can be tuned to that of the excitation. To assess the efficiency of the device, the response amplitude of a single-degree-of-freedom harmonically induced structure controlled by the ATMID is compared with those of the passive-controlled and uncontrolled structures. Results show that in the frequency band where the effectiveness of the passive device with a mass ratio of 0.2 is degraded and even destructed, the adaptive device with a mass ratio of 0.1 and diverse inertance behaves impressively. As a result, notable oscillation suppression is obtained using the proposed adaptive device compared with passive-controlled (56%) and uncontrolled cases (21%). The presented extensive variability in the frequency of the device utilizing its transmission ratio of 0.45–2.2 leads the device to a superior level of oscillatory motion reduction in structural responses along an enlarged frequency band.
3 citations
TL;DR: In this paper, a mobility-based method was proposed to measure the vibro-acoustic properties of building parts in situ using a combination of incident plane wave sound pressure and membrane surface displacement information, measuring the sound pressure with a microphone and the membrane displacement by means of a Doppler vibrometer.
Abstract: The article focuses on the determination of the acoustic properties (sound transmission loss, sound absorption and transmission coefficient under acoustic plane wave excitation) of membrane-type of specimens by means of a combination of incident plane wave sound pressure and membrane surface displacement information, measuring the sound pressure with a microphone and the membrane displacement by means of a laser Doppler vibrometer. An overview of known measurement methods and the theoretical background of the proposed so-called mobility-based method (MM) is presented. The proposed method was compared with the conventional methods for sound transmission loss and absorption measurement in the impedance tube, both numerically and experimentally. Finite element model (FEM) simulation results of two single layer membrane samples of different shape configurations were compared, amongst which six different variations of the backing wall termination. Four different approaches to determine the sound transmission loss and two methods to determine sound absorption properties of the membranes were compared. Subsequently, the proposed method was tested in a laboratory environment. The proposed MM method can be possibly used to measure the vibro-acoustic properties of building parts in situ.
2 citations
References
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TL;DR: In this paper, the authors show that thin membrane-type acoustic metamaterials can serve as a total reflection nodal surface at certain frequencies, which implies that several membrane panels can be stacked to achieve broad-frequency effectiveness.
Abstract: We show experimentally that thin membrane-type acoustic metamaterials can serve as a total reflection nodal surface at certain frequencies. The small decay length of the evanescent waves at these frequencies implies that several membrane panels can be stacked to achieve broad-frequency effectiveness. We report the realization of acoustic metamaterial panels with thickness ≤15 mm and weight ≤3 kg/m2 demonstrating 19.5 dB of internal sound transmission loss (STL) at around 200 Hz, and stacked panels with thickness ≤60 mm and weight ≤15 kg/m2 demonstrating an average STL of >40 dB over a broad range from 50 to 1000 Hz.
432 citations
TL;DR: In this article, the authors derived the radiation resistance of a finite rectangular panel from the total energy radiated to the far field, assuming that the panel is assumed to be supported in an infinite baffle.
Abstract: The radiation resistance corresponding to the natural modes of a finite rectangular panel is theoretically determined from the total energy radiated to the farfield. The panel is assumed to be simply supported in an infinite baffle. Asymptotic solutions for the low‐frequency region are derived, and curves covering the entire frequency range for various mode shapes and aspect ratios are obtained through numerical integration. When the ratio of the acoustic wavenumber to the panel wavenumber is a constant much less than unity, the radiation resistance for all modes is a minimum if the intranodal area (the area between adjacent node lines) is square, and increases with the aspect ratio of the intranodal area.
383 citations
TL;DR: In this article, the authors overview the active sound and vibration control field, first by putting it into a historical context, then by outlining the relevant control theory and implementations, and finally by describing some current practical applications.
Abstract: In many industrial and defense applications noise and vibration are important problems. The conventional method of treatment is to use passive damping techniques or to redesign the system. However, passive damping techniques are primarily effective at higher frequencies, and redesign is often costly and ineffective. In the last decade, active control of sound and vibration (at audio frequencies) has emerged as a viable technology to bridge this low-frequency technology gap. Recent developments have been propelled by the rapid technology growth in affordable and practical digital signal processing chips and, to a smaller degree, improvements in control transducers. In this article the authors overview the active sound and vibration control field, first by putting it into a historical context, then by outlining the relevant control theory and implementations, and finally by describing some current practical applications.
290 citations
TL;DR: In this article, active control of sound radiation from vibrating plates by oscillating forces applied directly to the structure is analytically studied, and it is shown that global attenuation of broadband radiated sound levels for low to mid-range frequencies can be achieved with one or two control forces, irrespective of whether the system is on or off resonance.
197 citations
TL;DR: In this paper, a theory on the generation mechanism of directional acoustic radiation from a supersonic jet is proposed based on the concept of instability of the shear layer at the boundary of the jet close to the nozzle.
Abstract: A theory on the generation mechanism of directional acoustic radiation from a supersonic jet is proposed. The theory is based on the concept of instability of the shear layer at the boundary of the jet close to the nozzle. Theoretical prediction of the directional wave pattern is found to agree with shadowgraphic observation.
139 citations