Showing papers in "Applied Acoustics in 1997"

TL;DR: In this paper, a phenomenological model for sound propagation in porous media is developed, where the relaxation model parameters (characteristic times) are chosen by comparison to three existing models: Delany and Bazley's empirical equations; the Biot-Allard microstructural model; and Champoux and Stinson's generalized, microstructural model.

TL;DR: In this article, three theoretical models are used for the prediction: an infinite plate model, a baffled plate model and a room-plate-room model, and the results demonstrate the strong modal behaviour of low-frequency sound transmission.

TL;DR: In this article, the stiffness and damping of rail fasteners, and in particular the elastomeric pads inserted between the rail and sleeper, are important parameters determining the dynamic behaviour of railway track.

TL;DR: Optical microphone technology is reviewed in this article, where a classification scheme is introduced which utilizes the transduction mechanism as the primary sorting criterion and a discussion of performance criteria follows, with an emphasis on sensitivity.

TL;DR: In this article, a general overview of the benefits and limitations of the maximum length sequence (MLS) technique in building acoustics is presented, and an approach is described to investigate the influence of time variances on the use of synchronous averaging.

TL;DR: A review of noise modelling techniques for shipping and wind noise sources covering the frequency range 50 Hz to 3 kHz is given in this article, focusing mainly on work done from 1980 onwards, and results presented in terms of horizontal and vertical directionality and the responses of hydrophone arrays.

TL;DR: In this paper, transfer matrices have been derived for side inlet and side outlet elements for typically small mean flow Mach numbers for a stationary medium and for acoustically long chambers.

TL;DR: In this article, the ultrasonic attenuation of another class of auxetic materials, microporous polymers, and in particular ultra-high-molecular weight polyethylene (UHMWPE), was examined experimentally, in comparison with a microporus positive v form of UHMW PE and conventionally processed UHMPE, with the highest measurable value being α mn = 47 dB / cm for the auxetic material.

TL;DR: In this paper, the acoustic behavior of porous materials with a rigid frame has been investigated experimentally, and an empirical equation for the structural characteristic has been derived as a function of frequency, porosity and the pore diameter.

TL;DR: In this article, a direct mathematical model for the prediction and identification of transverse cracks in beams with different end conditions is presented, based on the assumption that the beam is an Euler-Bernoulli beam.

TL;DR: In this paper, the authors investigated complaints about poor sound insulation between dwellings and found that the main noises heard by complainants are music/television/radio, voices, footfalls, closing and banging doors, sockets, switches, impacts on kitchen work surfaces and plumbing noises.

TL;DR: In this research, a semi-empirical method has been developed and a computer program has been written to correct the calculations of existing theoretical formulae or computer simulation models with an empirical database based on physical scale model or site measurements.

TL;DR: In this article, four psychoacoustic tests were designed in order to study the human echolocation ability, i.e., the process of auditive perception of obstacles without the use of vision.

TL;DR: In this paper, it was shown that grain is a strong acoustical absorber, the attenuation coefficient increasing roughly as the square root of the frequency, and that sound is transmitted over longer distances in grains with a larger interkernel spacing, such as corn and soybeans.

TL;DR: In this article, the authors investigated the relationship between the diffusion of sound and the acoustical quality of halls and found that the correlation between the surface diffusivity and the acoustic quality of the halls was surprisingly high (r2 > 0.6).

TL;DR: In this article, a theoretical model is developed for the inverse-square sound speed (or void fraction) profile, which is also based on turbulent transport but in the presence of a constant stress layer immediately beneath the surface.

TL;DR: In this paper, three classes of acoustic comfort (CAC) have been defined in a guideline of the German Engineering Society (VDI 4100): (a) by describing certain subjective impressions of noise protection in the different CACs and (b) by quantifying appropriate values in well known acoustic indices.

TL;DR: CANARY as mentioned in this paper is a ray-based model of ambient noise and noise coherence designed for hull-mounted arrays composed potentially of individually directional (or baffled) hydrophones, which can produce results compatible with wave treatments such as RANDI.

TL;DR: In this article, a new theoretical model for predicting the sound absorption of perforated absorber systems is presented, which includes the effect of the diffraction phenomenon caused by impedance discontinuities of the boundary surface, which has been disregarded in the past studies.

TL;DR: In this article, a stationary tire is excited by an electrodynamic shaker and a description of surface velocity is obtained, and a reciprocity technique is used to measure the transfer functions which describe the transmission of sound from points on a tyre wall to a point inside a vehicle.

TL;DR: In this paper, an automated, computer-based system was designed to quantify infestation of internally feeding larvae in a grain sample by obtaining data correlated with the location of sound sources.

TL;DR: The rationale, background and principles of International Standards 9614-1 and 9613-2 for the determination of source sound power from measurements of sound intensity are described and explained.

TL;DR: It is concluded that the method is convenient, accurate and reliable provided that a few simple rules are observed.

TL;DR: In this article, the smallest eigenvalue of the spectral matrix is used as the threshold eigen value, which guarantees that the obtained projection matrix is an estimate of the noise subspace.

TL;DR: In this article, a computer-aided test method was developed to measure the acoustic parameters of absorber specimens in impedance tubes, and a specially written Windows program, implementing the single microphone fast Fourier transform method, enables quick and precise measurement of the impedance and absorption coefficient of samples at normal sound incidence.

TL;DR: In this paper, the average value of the bottom scattering strength was found to be between −26 and −34 dB in that frequency band, and the usual frequency range for detection of marine life of 100-500 kHz was used.

TL;DR: In this article, the waveform and frequency spectra of human footfall (walking, running and jumping), of sand balls, sand bags and dropped tires, and of the standard tapping machine were investigated.

TL;DR: In this article, a round robin on the measurement of sound insulation in buildings (airborne sound insulation between two rooms according to ONORM S 5100-1, very similar to ISO 140-4; impact sound level according to Onorm S 5 100-2; airborne sound insulation of a window according to DIN 52210-5) has been performed according to ISO 5725 and EN 20140-2 (ISO 140-2).

TL;DR: In this article, the performance of ALFID's noise-shielding components, which include an enclosure for passive reduction of ambient noise, and an electronic system for active detection and masking of sounds originating outside the grain sample container, was investigated.