Sound Field Distribution Research Articles

Fabrication and properties of the thickness mode ultrasonic transducer based on 0.15Pb(Mg1/3Nb2/3)O3-0.38PbHfO3-0.47PbTiO3 piezoelectric ceramics

In this paper, the 0.15Pb(Mg1/3Nb2/3)O3-0.38PbHfO3-0.47PbTiO3 ternary piezoelectric ceramic fabricated by the partial oxalate method that exhibits superior electrical properties (d33 = 447 pC/N and kt = 56.9%) and excellent thermal stability of the piezoelectric properties below TC was studied. The newly discovered piezoelectric ceramic had a high Curie temperature (Tm = 297 °C), this feature was used to fabricate a novel single-element ultrasonic transducer whose center frequency was 2.15 MHz, with a −6 dB bandwidth of up to 79.07%, and a sensitivity that reached −31.75 dB. The result of the experiment agreed well with that of PiezoCAD software based on the KLM model. This transducer's outstanding thermal stability below TC can be widely used in non-destructive evaluation. At the same time, we measured the sound field distribution of the ultrasonic transducer. The focal length was measured approximately 47 mm. An obvious main lobe was clearly seen from the z–x scan. The power was measured as 17.98 mW; the beam width of –3dB was 3.5 × 3.6 mm; and the area was 9.83 mm2 according to the FDA and IEC standards.

Numerical simulation of ultrasonic heat meter by multiphysics coupling finite-element simulation software

Objective: To increase heat calculation accuracy, the numerical simulation of the ultrasonic heat meter is explored by multiphysics coupling. Methods: The COMSOL, a multiphysics coupling finite-element simulation software, is used to build the coupling model of the sound field, structure field, and electric field. The propagation of ultrasonic waves in heat meters is simulated, and its sound field distribution in pure water is analyzed. According to the operating conditions of ultrasonic heat meters, the influence of impurities with different concentrations on ultrasonic propagation is analyzed. The end-face sound pressure levels of the incident transducer and the receiving transducer are compared to obtain the attenuation laws of ultrasonic waves in the liquid-solid two-phase flow. Results: The main lobe and multiple side lobes exist during the propagation of ultrasonic waves. The energy of the main lobe is higher than that of the side lobes. Bubbles resonate under the action of the sound field. Also, bubbles of different diameters correspond to different resonance frequencies, which have larger sound pressure than that of the incident sound field. Most of the sound waves are reflected at the liquid-solid interface, while some of them continue to propagate through the media, affecting the sound pressure distribution on the end-face of the receiving transducer, thereby affecting the measurement accuracy of the ultrasonic heat meter. Conclusion: The reliability and detection efficiency of the heat meter is improved, which is significant and theoretically valuable.

Low frequency sound field reconstruction in a non-rectangular room using a small number of microphones

An accurate knowledge of the sound field distribution inside a room is required to identify and optimally locate corrective measures for room acoustics. However, the spatial recovery of the sound field would result in an impractically high number of microphones in the room. Fortunately, at low frequencies, the possibility to rely on a sparse description of sound fields can help reduce the total number of measurement points without affecting the accuracy of the reconstruction. In this paper, the use of Greedy algorithm and Global curve-fitting techniques are proposed, in order to first recover the modal parameters of the room, and then to reconstruct the entire enclosed sound field at low frequencies, using a reasonably low set of measurements. First, numerical investigations are conducted on a non-rectangular room configuration, with different acoustic properties, in order to analyze various aspects of the reconstruction frameworks such as accuracy and robustness. The model is then validated with an experimental study in an actual reverberation chamber. The study yields promising results in which the enclosed sound field can be faithfully reconstructed using a practically feasible number of microphones, even in complex-shaped and damped rooms.

Analysis of sound field distribution of angle dimension in deep ocean bottom bounce area and its application to active sonar vertical beam pitch

In the deep ocean environment, the sound energy from the direct path is very hard to illuminate a target located in the shadow zone. To solve the problem, the bottom bouncing technique, in which the vertical transmitting beamforming and the bottom bouncing are used to illuminate the target in the shadow zone, provides a potential way. However, due to the sound field interference in the bottom bouncing area in the deep ocean environment, the sound energy in the bottom bouncing area is fluctuant, which produces several discrete detectable areas. In order to detect underwater targets in these areas when using an active sonar with a transmitting vertical linear array, the selecting of reasonable vertical transmitting beam angles is necessary. Therefore, the relationship between the discrete detectable area and the transmitting vertical angle in deep ocean is very important for the active sonar using a transmitting vertical linear array. In this paper, it is shown that the sound field fluctuation in the bottom bouncing area is due to the energy fluctuation of the rays having different grazing angles. And the active sonar can achieve high noise gain in a detectable area when the vertical transmitting angle is equal to the grazing angle of the sound ray with the peak energy. To obtain a high noise gain of the active sonar using the vertical transmitting array, an efficient method to estimate the grazing angle of sound rays with peak energy according to the sound field distribution of angle dimension is proposed, which is helpful for selecting a group of best vertical transmitting angles. Meanwhile, a transmitting signal which contains a group of subpulses is designed. Furthermore, each subpulse is applied to the whole transmitting array by using the vertical steering to illuminate a certain detectable area in the bottom bouncing area. By doing so, a subpulse steered to the previously selected vertical angle will ensure a high transmitting array gain in a detectable area, and all of pulses will illuminate the whole detectable areas with high array gains almost simultaneously. Numerical simulations show that the proposed method is stable and efficient, and has good noise gain in the shadow zone (where almost no direct path exists) in the deep ocean environment.

Experimental analysis of sound field in the tire cavity arising from the acoustic cavity resonance

The acoustic cavity resonance noise inside the tire-wheel assembly is known to contribute to audible noise in the passenger compartment of vehicles, but it is difficult to attenuate the effect of tire cavity resonance noise. The purpose of this paper is to experiment and analyze the sound field in the tire cavity of a revolving tire through a customized sound pressure sensor fixed on the inner surface of the tire, and to obtain the distribution and frequency characteristics of sound field. Furthermore, the paper concerns the effects of the inflation pressure, the running velocity, and the load on the sound pressure distributions and its frequency characteristics, and the influence of these parameters are analyzed. The research is helpful to understand and attenuate the tire acoustic cavity resonance.

Sound field measurement and evaluation research for radiated acoustic fields in amplitude-variable sonochemical systems

The content of this study is based on the background of sonochemistry processes. First, the hydrophone is used to measure the sound pressure in the reactor (the experimental ultrasonic frequency range is 20 ± 1 kHz). The sound pressure signals are processed by threshold method, Kalman filter algorithm, and five-point three-time smoothing method. These methods eliminate singular items in the sound pressure signal, filter noise, smooth burrs, and so on. In addition, the sound intensity value is calculated by dual hydrophone method. In this paper, the average intensity of ultrasonic cavitation is studied. The radial distribution and longitudinal distribution of cavitation intensity of the same tool head are studied, and the effects of different power and different tool heads on cavitation intensity are also discussed in this paper. The experimental results show that the instrument designed in this paper can effectively measure the distribution of ultrasonic sound field and evaluate the performance of the tool head. We can infer from the experiments that the performance of the diamond tool head is better than that of the nine-section whip and the dumbbell tool head.

Research on creation and evolution of artificial diffuse sound field

In a closed space, it is difficult to create a diffuse sound field by using a single source in the reverberation tank. In this paper, a methodology for construction of diffuse sound field using multiple source excitation is proposed. Proposed methodology is based on space processing technique for a single source sound field and also involves reciprocity of sound field transfer function. Firstly, the analytical method of acoustic excitation reverberation field is studied and subsequently the sound pressure equation for excitation reverberation sound field in case of multi sound is obtained. In addition, the numerical method to observe the influence of sound source distribution upon uniformity of sound field is studied by the acoustic analysis software ACTRAN. Finally, diffuse sound field in a glass tank of 1.5 m × 0.9 m × 0.6 m dimensions, is constructed by using 30 emission transducers of the same type. In the end, the diffuse sound field is scanned using scanning array and is then evaluated by measuring the standard difference of the space distribution of sound field. The results show that the standard deviation of the sound pressure distribution in the diffused sound field in comparison with 30 transmitting transducers simultaneously within the reverberation control area is not greater than 3.9 dB under the narrow band condition. Hence, it clearly illustrates that construction of diffused sound field by this method is definitely a viable option.

Prediction of sound fields after propagation through sound barriers by CNN and DCNN algorithms

Sound fields are affected by the size of the space and the surrounding environments. The ray tracing method analyze the sound propagation through geometric constraints. For prediction of sound fields in a real-time to investigate the influence of surrounding environments, an effective calculation method is required. During the prediction, it is necessary to calculate the sound field distribution according to the layout of equipment or sound reflecting devices to minimize noise in working spaces. This procedure is required for an optimal arrangement of barriers according to noise sources. To improve this repetitive work, it is devised to develop a machine learning model that predicts the change in the sound field according to the position of sound barrier through CNN and DCNN algorithms. Training data were generated by using a commercial tool. The proposed approach recognizes the characteristics of sound fields at spaces after acoustic barriers.

Acoustic Coupling between Resonator Tubes in Quartz-Enhanced Photoacoustic Spectrophones Employing a Large Prong Spacing Tuning Fork.

A theoretical model describing the acoustic coupling between two resonator tubes in spectrophones exploiting custom-made quartz tuning forks (QTFs) is proposed. The model is based on an open-end correction to predict the optimal tube length. A calculation of the sound field distribution from one tube exit allowed for the estimation of the optimal radius as a function of the QTF prong spacing and the sound wavelength. The theoretical predictions have been confirmed using experimental studies employing a custom QTF with a fundamental flexural mode resonance frequency of 15.8 kHz and a quality factor of 15,000 at atmospheric pressure. The spacing between the two prongs was 1.5 mm. Spectrophones mounting this QTF were implemented for the quartz-enhanced photoacoustic detection of water vapor in air in the mid-infrared spectral range.

The Ambisonic Recordings of Typical Environments (ARTE) Database

Everyday listening environments are characterized by far more complex spatial, spectral and temporal sound field distributions than the acoustic stimuli that are typically employed in controlled laboratory settings. As such, the reproduction of acoustic listening environments has become important for several research avenues related to sound perception, such as hearing loss rehabilitation, soundscapes, speech communication, auditory scene analysis, automatic scene classification, and room acoustics. However, the recordings of acoustic environments that are used as test material in these research areas are usually designed specifically for one study, or are provided in custom databases that cannot be universally adapted, beyond their original application. In this work we present the Ambisonic Recordings of Typical Environments (ARTE) database, which addresses several research needs simultaneously: realistic audio recordings that can be reproduced in 3D, 2D, or binaurally, with known acoustic properties, including absolute level and room impulse response. Multichannel higher-order ambisonic recordings of 13 realistic typical environments (e.g., office, cafè, dinner party, train station) were processed, acoustically analyzed, and subjectively evaluated to determine their perceived identity. The recordings are delivered in a generic format that may be reproduced with different hardware setups, and may also be used in binaural, or single-channel setups. Room impulse responses, as well as detailed acoustic analyses, of all environments supplement the recordings. The database is made open to the research community with the explicit intention to expand it in the future and include more scenes.

Recovery of non-stationary free field based on pressure and acceleration measurements in a noisy environment

In a noisy environment, the interested sound field is interfused with the non-stationary incoming field from the back side of the measurement plane and the scattered field caused by the incoming wave falling on the surface of the target source. In order to remove the non-stationary incoming and scattered fields simultaneously, a recovery method of the non-stationary free field with the pressure and particle acceleration measurements is proposed. First, the mixed time-evolving pressure and particle acceleration are firstly measured on one measurement plane, where the particle acceleration is obtained by the finite difference approximation with the aid of an auxiliary measurement plane; Then, two physical relations are employed to deduce a forward complete recovery formulation of the target source in the noisy environment. One relation contains two impulse response functions relating the time-wavenumber pressure spectrum to particle acceleration and pressure spectra, respectively, and the other is the surface reflection coefficient of the target source relating the scattered field to the incoming field. Finally, the mixed pressure and particle acceleration are substituted into the recovery formulation, and the time-evolving pressure radiated by the target source in free-field is recovered. Thereby, the proposed method possesses a significant feature of real-time recovery of the non-stationary free field. A circular piston fixed on an infinite rigid baffle and two monopole sources are designed in a numerical simulation to test the performance of the proposed method. The simulation results attest that the proposed method not only can recover the time-evolving pressure radiated by the target source in free-field at any space points, but also recover the space distribution of the non-stationary sound field of the target source in free-field at different time instants effectively. An experiment with two speakers embedded in a planar steel plate and a speaker is further employed to verify the validity of the proposed method.

A Preliminary Study of Seeding Absence Detection Method for Drills on the Soil Surface of Cropland Based on Ultrasonic Wave without Soil Disturbance

Seeding absence detection is essential during seeding operation, since it affects the subsequent crop performance. Existing methods cannot detect the seeding absence position immediately after planting without soil disturbance. In this paper, a nondestructive detection method for finding out the seeding absence position of drills is put forward. It focuses on the echo energy reflected by the circle energy inside the tilled cropland soil, to which the sensor is attached directly on the soil surface, not on ultrasonic waves that penetrate the soil-seed medium below tilled soil. Firstly, the energy circle is used to analyze the sound field distribution characteristics of the sensor in cropland soil. According to the size difference of the seeding absence length value and energy circle diameter, the total energy for three different cases with eight steps for each case is discussed in detail, and in order to find the left and right boundary lines and the length value of seeding absence, a program is designed to help with calculating four base positions automatically. At last, the nondestructive detection method is evaluated by the experiments, and the results demonstrate that the proposed method is accurate, efficient, and convenient in finding the seeding absence position of drilling seeds on the soil surface without soil disturbance.

The Analysis of Acoustic Propagation Characteristic Affected by Mesoscale Cold-Core Vortex Based on the UMPE Model

The ocean mesoscale vortex can make uneven distribution of sound energy, which has a significant impact on underwater acoustic equipment, weapons and submarine warfare. Based on the observed data of 2014 West Pacific sea oceanographic survey, the influence of the properties, strength, position and depth of the mesoscale vortex on the acoustic propagation characteristics is simulated by the parabolic equation. Our observed vortex is a typical cyclone-type cold vortex in the Kuroshio extension body, and the cold water turns on intensely at the center of vortex. The effect depth of vortex is 500 m, and then, the parabolic equation of acoustic model is used to analyze and simulate the impact of mesoscale cold-core vortex on acoustic transmission loss. Results show that the horizontal perturbation of the surface velocity caused by mesoscale vortex has a great influence on the spatial distribution of water sound field. The cold vortex makes the position of the convergence zone move forward, with the width reduced, and the gain efficiency enhanced. When sound propagates outside of the cold-core vortex, compared with inside of the cold-core vortex, the assembled areas are backward, with the width increased, and gain effect weakened. The non-uniform hydrological environment caused by the ocean mesoscale vortex is a key modulating factor of the abnormal variation of acoustic energy in spatial distribution.

Numerical calculation and measurement for the focus field of concave spherical acoustic lens transducer

How to accurately calculate the sound field formed by acoustic lenses is an important basis for the design of acoustic lens transducers. The radiation sound field distribution of the physical model of acoustics lens is simulated by numerical methods, including the ray propagation method and the wave propagation method. The ray propagation method can only get the focal length without considering the wave characteristics property, while the wave propagation method takes into account the amplitude and phase factors of the wave, and by which the distribution of the whole sound field can be got. The relationship between the property of refractive wave and incident angle of incident wave is analyzed, and theoretical results of the distribution of the focal field are obtained. The actual sound field of the real transducer is measured by acoustic field scanning system, and the measured results of focal length and focal area are obtained. The comparison and analysis of the numerical data and measured data show that the wave propagation method can be used to predict the focus field of concave spherical acoustic lens transducer accurately and effectively.

Modeling of Acoustic Emission Generated by Filter Capacitors in HVDC Converter Station

The acoustic noise generated by filter capacitors in a high voltage direct current (HVDC) converter station will have a serious negative impact on the residents' lives and the ecological environment. Though accurate enough, traditional modeling methods based on either boundary element method (BEM) or finite element method (FEM) are almost impossible to reconstruct sound field for whole HVDC station filter array because of their extremely high demand for computing resources. To deal with this problem, this paper proposes a novel Tikhonov Regularization Equivalent Source Method (TRESM)-based filter capacitor acoustic model. By constructing multiple point-sound source models, the acoustic characteristics of the actual filter capacitor are simulated and the original sound field is reconstructed. The accuracy of the proposed model is verified by the experimental results and the sound field distribution characteristics of the three-phase filter capacitor array are observed and analyzed using the proposed model.

In Design of an Ocean Bottom Seismometer Sensor: Minimize Vibration Experienced by Underwater Low-Frequency Noise

Ocean Bottom Seismometers (OBS) placed on the seafloor surface are utilized for measuring the ocean bottom seismic waves. The vibration of OBS excited by underwater noise on its surface may interfere with its measured results of seismic waves. In this particular study, an OBS was placed on the seabed, while ray acoustic theory was used to deduce the sound field distribution around the OBS. Then using this information, the analytical expression for the OBS vibration velocity was obtained in order to find various factors affecting its amplitude. The finite element computing software COMSOL Multiphysics® (COMSOL) was used to obtain the vibration response model of the OBS which was exposed to underwater noise. The vibration velocity for the OBS calculated by COMSOL agreed with the theoretical result. Moreover, the vibration velocity of OBS with different densities, shapes, and characters were investigated as well. An OBS with hemispherical shape, consistent average density as that of the seafloor, and a physical structure of double tank has displayed minimum amplitude of vibration velocity. The proposed COMSOL model predicted the impact of underwater noise while detecting the ocean bottom seismic waves with the OBS. In addition, it provides significant help for the design and optimization of an appropriate OBS.

Experimental investigations on sound energy propagation in acoustically coupled volumes using a high-spatial resolution scanning system.

The aim of this work is to study the sound field distribution in an experimental scale-model of two coupled rooms. An automatic scanning mechanism moves a microphone in small grid steps to measure room impulse responses at each grid point. The measurements cover the entire two-dimensional area of the coupled rooms. Sound energy distributions can be analyzed in the form of animated visual displays, revealing sound propagation across the coupling aperture and inside each room. This paper describes the measurement results, and the analysis method, which offer deep insights into the temporal development of a sound field in coupled spaces.

The Experiment of Acoustic Levitation and the Analysis by Simulation

An acoustic levitation test bench was built to successfully suspend a small ball of a certain density. It was found that the smaller the diameter and density of the suspended sample, the easier it is to suspend. The diameter of the sample should not be larger than 1/4 - 1/3 of the wavelength of the acoustic wave. In addition, as the sound pressure increases, the sound flow also affects the stability of the acoustic levitation. Comsol was used to nu-merical simulation the spatial sound field, pressure field and particle ve-locity distribution of different suspension cavity heights, and the factors affecting the acoustic levitation capacity were analyzed.

Sound field study of a building near a roadway via the boundary element method

A two-dimensional boundary element method with a constant element type was adopted to study the sound field of a building near a roadway. First, a factor analysis of the computed results has been done, which include the element length, the Hankel functions’ calculation accuracy, and numerical integration accuracy. Then, boundary element method is applied to calculate building attenuation with different building aspect ratios and different frequencies with balconies, followed by drawing of the sound field distribution diagram. The calculation results revealed the following: (1) a wider building results in a more severe sound attenuation; (2) balconies on different floors produce a reduction of approximately 15 dB for broadband spectral characteristics of A-weight road traffic noise, and the maximum values appear at the bottoms of balconies; (3) for the points in the balconies, higher sound frequencies are correlated to larger insertion loss, with the insertion loss increasing from 3 dB to >10 dB when the sound frequency increases from 20 to 4000 Hz; (4) calculations of three typical frequencies indicate that the insertion loss of 500 Hz (main frequency of heavy vehicles) is 6 dB less than that of 800 Hz (main frequency of light vehicles), i.e. the flow control of heavy vehicles could conspicuously improve the ambient acoustic environment of buildings near a roadway.

Impedance-matching acoustic bend composed of perforated plates and side pipes

In this article, we propose a design for an impedance-matching acoustic bend. The bending structure is composed of sub-wavelength unit cells containing perforated plates and side pipes that allow the mass density and the bulk modulus of each unit cell to be tuned simultaneously. The refractive index and the impedance of the acoustic bend can therefore be modulated simultaneously to guarantee both the bending effect and high acoustic transmission. The results of simulation of the sound pressure field distribution show that the bending effect of the proposed impedance-matching acoustic bend is very good. Transmission spectra are calculated for both the impedance-matching acoustic bend and an acoustic bend composed of the perforated plates alone for comparison. The results indicate that the impedance-matching acoustic bend successfully improves the impedance ratio while also obviously increasing the transmission.