Impulse Sound Research Articles

Optimization for Emission Frequency of Oceanic Impulse Sound Source Logging

Gao, X.; Zhu, J.; Fu, H., and Hao, X., 2020. Optimization for emission frequency of oceanic impulse sound source logging. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 124–129. Coconut Creek (Florida), ISSN 0749-0208.In the exploration and development of offshore oilfields, the requirements for the detection distance and accuracy of underground geological structures are increasing day by day. When the traditional acoustic logging technology is used in oceanic logging, the formation structure is complex, and the reflected signal is very weak, which makes it difficult to extract the reflected signal and accurately identify the reflector orientation. The plasma impulse sound source is used as the emission source of the technology of ocean exploration while drilling, which has the characteristics of high power, wide frequency band, energy accumulation, and controllable and repeatable excitation, which can not only enhance the detection distance of traditional acoustic logging, but also detect the geological structure, fracture types, and strike around the well. In this article, sound depth detection technology is applied to study the selection of the dominant emission frequency band of the stimulated sound source based on the establishment of the geological interface depth detection model with different borehole diameter parameters. The results show that: when the well diameter is 0.1524, 0.2159, 0.2445, and 0.3112 m, 5, 3.8–4.2, 3.5–4, and 3 kHz are selected as the dominant excitation frequency bands, and the detection distance can reach tens of meters or even hundreds of meters. This research provides a reference for the subsequent application of impulse source in offshore logging.

Efficient modeling of long range impulse sound propagation in three dimensions

Sound characteristics close to the ground strongly depend on the atmospheric and ground properties in terms of amplitude, shape, and time of arrival. Time-domain numerical modeling is able to accurately account for outdoor sound propagation and is valuable to decipher the interactions between the refractive, scattering, and ground effects. It remains computationally challenging for three-dimensional long range simulations. A high-order parallel Finite-Difference Time-Domain solver with the moving frame approach is presented, featuring accurate time-domain impedance boundary conditions and very efficient convolutional perfectly matched layers to artificially truncate the computational domain. The design of the absorbing boundaries is based on a stability analysis of the time integration scheme and is shown to optimize the absorption properties for grazing waves. The model allows for accurate propagation of impulse sounds in 3D over several hundreds of meters and up to 1000 Hz using a personal laptop with a simulation duration of a few hours. The numerical predictions are compared to experimental measurements under different weather conditions, with a special focus on the sensitivity to the mean vertical wind profile and the ground properties.

Scattering of Stationary and Non-stationary (Impulse) Sound by Viscous–Elastic Cylindrical Layers

Scattering of Stationary and Non-stationary (Impulse) Sound by Viscous–Elastic Cylindrical Layers

Diffraction of Impulse Sound Signals on Spheroidal Body, Put in Plane Waveguide

With the help o f the Fourier t ransform and characteristics of the stationary (continuos) sound signal are calculated the impulses, scattered by the ideal spheroid, placed in the waveguide. In the first part of the paper is presented the method of the imag inary sources and imag inary scatterers from the solution of the problem of the sound diffraction on the spheroidal body, put in the plane waveguide. In the second part of the paper are calculated the impulse signals with different filling, scattered by the the ideal soft spheroid, placed in the plane waveguide.

Range and Velocity Estimation Based on Phase Interference of Subband-divided and Time-delayed Impulse Sound to a Moving Target

Range and Velocity Estimation Based on Phase Interference of Subband-divided and Time-delayed Impulse Sound to a Moving Target

Accuracy of Assessing the Level of Impulse Sound From Distant Sources

Impulse sound events are characterised by ultra high pressures and low frequencies. Lower frequency sounds are generally less attenuated over a given distance in the atmosphere than higher frequencies. Thus, impulse sounds can be heard over greater distances and will be more affected by the environment. To calculate a longterm average immission level it is necessary to apply weighting factors like the probability of the occurrence of each weather condition during the relevant time period. This means that when measuring impulse noise at a long distance it is necessary to follow environmental parameters in many points along the way sound travels and also to have a database of sound transfer functions in the long term. The paper analyses the uncertainty of immission measurement results of impulse sound from cladding and destroying explosive materials. The influence of environmental conditions on the way sound travels is the focus of this paper.

CAD/CAEと打撃音を利用したエンドミル加工時のびびり振動の予測と回避

CAD/CAEと打撃音を利用したエンドミル加工時のびびり振動の予測と回避

Microprocessor‐based apparatus for direct evaluation of environmental impulsive sounds

A new apparatus for direct evaluation of environmental impulse sounds was designed and realized on the basis of an improved formulation of the noise disturbance level LDI and by a suitable digital technique. The noise disturbance meter is equipped with a microprocessor and 32 kbyte of RAM, enabling it to perform uninterrupted measurements for time intervals from seconds to hours. Since the apparatus can be tuned to different time constants, this allows fast, average, or low‐noise fluctuations to be detected, covering a wide range of environmental impulse noise situations. Some experimental tests carried out on a few impulsive noise samples of different origin showed that the noise disturbance level can give suitably greater weight to the fast fluctuation component of noises, in comparison with the conventional indices. Also, results indicated that the time constant is a critical parameter in measuring the impulse component of a sound. This stimulates further investigations to find the ‘‘optimum’’ time constant in measurements involving impulse sound evaluation and suggests that the study should be extended toward the investigation of a subjective ‘‘cutoff frequency’’ related to the noise fluctuation sensitivity.

On the level-dependent penalty for impulse sound

At relatively low A-weighted equivalent levels (Leq), road-traffic sounds are rated to be less annoying than impulse sounds. The differences, however, decrease with increasing Leq of the sounds, which indicates that the penalty for impulse sound seems to be level dependent. It was questioned whether the decrease of the penalty with increasing Leq might, at least partly, have been a consequence of the use of the ten-point rating scale. In experiments 1 and 2, the relevance of the level-dependent correction was therefore studied further by using the method of adjustment. The mean results again showed that, at least for gunfire sounds (small arms), the penalty is level dependent. The drawing of firm conclusions, however, was hampered by a relatively large bias in the adjustments. In addition, the overall size of the penalty was lower than obtained in previous rating experiments. The question about the relevance of the level-dependent penalty was reopened in experiment 3 by applying the method of paired comparison. The results confirm the previous findings obtained with the rating experiments: For gunfire sounds at relatively low indoor Leq values, a penalty of about 10 dB is required, and a penalty lower than 5 dB can be applied only in conditions with rather high sound exposure. The results further showed that especially at indoor Leq values higher than about 45 to 50 dB(A), application of a negative penalty may become relevant for specific sounds such as those produced by the 0.50-in. machine gun. Consequently, acoustic measures from which to predict the value of the penalty are highly needed.

Impulse Sound Level Meter Recommended by IEC

Impulse Sound Level Meter Recommended by IEC

Research and Development in Hydroacoustic Impulse Sound Sources

Research and Development in Hydroacoustic Impulse Sound Sources

A note on the limitations in the use of the impulse precision sound level meter

The limitations in the use of the Impulse Precision Sound Level Meter for the assessment of the sound energy of recurrent impact noise have been investigated. For repetition rates above 30 impacts per second the meter reading and level predicted by an energy law agree to within ±2 dB. Below 30 impacts per second, for pulses with decay times in the range 2 to 28 msec, a simple empirical correction applied to the meter reading will produce results that follow the energy law. For decay times in excess of 28 msec simple corrections are not adequate and therefore the Impulse Sound Level Meter cannot be used in practice.