Showing papers in "Applied Acoustics in 1998"

TL;DR: In this paper, a study on the application of sound pressure and vibration signals to detect the presence of defects in a rolling element bearing using a statistical analysis method is presented, which is most suitable with random signals where other signal analysis methods based on the assumptions of deterministic signals are not applicable.

TL;DR: In this article, the insertion loss of rectangular, T-shaped and cylindrical edged noise barriers with rigid, absorbing and soft surfaces was studied. But the authors only used the boundary element numerical modeling method.

TL;DR: This paper shows how hidden Markov models (HMMs) can be used to build an environmental noise recognition system based on a time-frequency analysis of the noise signal.

TL;DR: In this article, an extensive noise survey carried out in the city of Pamplona, Spain over 2 years has allowed us to elaborate a detailed daytime acoustic map of this city, and the degree of noise annoyance in the community and its relationship with the measured noise levels has also been studied by means of a social survey.

TL;DR: In this paper, the dynamic response of a Timoshenko beam resting on a Winkler-type elastic foundation acted upon by a moving concentrated mass is analyzed and compared with the corresponding behavior of an equivalent moving force neglecting the inertial effects of the mass.

TL;DR: In this article, the relationship between cavity length and wavelength of sound to attenuate noise is discussed. But the authors do not present detailed mathematical expressions for the design of quarter wave resonators, rather they illustrate the design principles involved for practical applications and demonstrate that the advantage of such resonators is their simplicity of design.

TL;DR: In this article, the effect of stiffness and damping on noise transmission loss of the honeycomb sandwich panels is investigated, and the experimental results of noise transmission losses for both aircraft sidewall aluminum panels and fiber reinforced concrete panels are obtained.

TL;DR: In this article, the improvement on the acoustic transmission loss of a duct by adding some Helmholtz resonators is discussed, and the results show that agreement of the calculated transmission loss with its related measurement is quite good at frequencies above 200 Hz.

TL;DR: In this article, a detailed analysis is carried out to clarify the mechanisms governing the acoustic performance of a permeable membrane and the effects of various material parameters, including mass and permeability.

TL;DR: In this paper, an improved diffraction-based method for calculating the insertion loss of a single, finite length, three-dimensional barrier was introduced. But the results of this method showed good agreement over a broad frequency range.

TL;DR: In this paper, various models for predicting aircraft noise around airports are described and the concept of "noise radius" has been formulated and implemented as a useful alternative to the conventional noise power distance relationship.

TL;DR: In this article, the authors examined the acoustic properties of double-leaf membranes, which have recently become widely used in the construction of membrane-structure buildings, and discussed the possibility of using doubleleaf membranes to construct the absorption structures.

TL;DR: In this article, the results of the noise emitted by machines are analyzed to predict an overall noise climate, and the results show that the noise levels in coal washeries, coal preparation plants, open cast and underground mining centres are very high when compared to accepted limits for occupational noise exposure.

TL;DR: In this paper, analytical and semi-empirical aircrafts trajectory and noise models have been developed and used for reducing aircraft noise levels under flight paths around airports, and the study results indicate various operational measures for reducing the aircraft noise level around airports.

TL;DR: In this paper, the main sources of noise in a noisy portable I. C. engine driven generator set have been identified, and a partial enclosure was designed for the generator set.

TL;DR: In this paper, an acoustical environment survey was carried out in six similar air conditioned landscaped offices in which human speech was considered to be the major source of complaint and both questionnaire and physical noise measurement were administrated.

TL;DR: In this paper, the sound insulation of thin finite-sized plates in finite-size walls is investigated at low frequencies, and the radiation efficiencies of finite and infinite plates are compared.

TL;DR: In this paper, the acoustic behavior of elastic porous materials has been investigated experimentally and the empirical equations for the acoustic parameters have been derived from comparative analysis of the experimental results and taking into account the complex mechanics of sound energy damping.

TL;DR: In this paper, a simple mass law based procedure developed by Sharp for the sound transmission loss (STL) prediction of an isotropic double wall is extended to the case of a double-leaf corrugated panel construction.

TL;DR: In this article, a simple methodology to estimate the main acoustical parameters of porous materials from very simple experimental tests is developed and validated on several conventional and innovative materials using a least squares regression based on measured reflection coefficient values of specimens to compute reliable values for sound absorbing materials parameters.

TL;DR: In this paper, a frequency domain analytical model is presented for a reverse-flow, three-duct, open-end perforated element muffler, starting with the basic equations of mass continuity, momentum balance and isentropicity.

TL;DR: In this article, the authors investigated and analyzed the noise reduction at low frequency by lining the cavity between two panels of a finite double panel structure with porous material, and found that the sound insulation of sandwich panels with air cavities containing and porous material is more effective than that of the single-layered panel at low-frequency.

TL;DR: In this paper, a correction term is introduced to enable point moment mobility to be measured directly, where the cross mobility at the receiver point is assumed to be small or zero, and the discrepancy between the measured and true mobility is defined as a function of the ratio between the unwanted vertical force and applied moment.

TL;DR: In this article, a new method to locate high speed moving sound sources based on a bilinear time-frequency transformation is proposed, where a microphone array, used as a directional sensor, is optimized in order to focus on the linear part of the frequency modulation due to the Doppler effect.

TL;DR: In this paper, the fundamental natural frequencies of vibration of simply supported and clamped polar orthotropic circular plates with and without internal (central) point supports are estimated by means of Rayleigh's method coupled with the deflection functions for the corresponding statically loaded systems.

TL;DR: In this article, a totally electronic approach is adopted to enhance the speech articulation in the main prayer hall (MPH) of the Kuwait State Mosque, and the layout of the sound reinforcement system and the loudspeakers' orientations were modified in order to minimize perturbations usually caused by reflections of sound waves and other interfering effects.

TL;DR: In this paper, simple models of air absorption and ground effect have been developed: the air absorption with the fully determined equivalent absorption coefficient, α, the ground effect with the A-weighted power level, L WA, and the ground coefficient, y.

TL;DR: In this paper, the authors present results of measurements of active noise control efficiency around noise barriers in an outdoor experiment around a real wall, which is limited to stationary noise, either harmonic or pink noise, created by a loudspeaker and controlled with the help of loudspeakers as secondary sources.