Acoustic Transmission Path Research Articles

Acoustic cloaking design based on penetration manipulation with combination acoustic metamaterials

The acoustic wave transmission manipulation ability is the most important performance for the acoustic metamaterials. To manipulate the acoustic transmission, the combination acoustic metamaterials structures are involved, and the two-directional acoustic penetration cloaking scheme are constructed. The combination acoustic metamaterials include chiral metamaterials and self-collimation metamaterials, the acoustic wave transmission path are manipulated to bypass from the acoustic scattering target in the penetration cloaking, and the target scattering stealth problem are effectively solved. In the end, the acoustic transmission manipulation performances are verified by numerical analysis with a finite-width acoustic metamaterial structure plates. The results provide technical support for design and application for acoustic transmission manipulation with acoustic metamaterials.

Surface Acoustic Wave (SAW)‐Based Sonoporation of Single‐Adherent‐Cell

Sonoporation refers to the formation of tiny transient pores in cell plasma membranes by using ultrasound to increase the permeability to bioactive materials. Recently, the Sonoporation technique has been widely researched in cell treatment applications, such as gene transfection. However, due to the random distribution of microbubbles, it is challenging to perform controllable and precise localized sonoporation of a target cell. In this work, a device based on the surface acoustic wave is developed to achieve a selective manipulation and cavitation of microbubbles. The device consists of a pair of microbubble positioning slant‐finger interdigital transducers (SFITs) for moving a selected microbubble in a two‐dimensional plane. Meanwhile, another narrow‐frequency‐band SFIT is integrated into the device for local cavitation control of the same microbubble. As a result, a microbubble can be transported orthogonal to and along the acoustic transmission path by continuously adjusting the input frequency and relative phase. Upon reaching the target cell, the selected microbubble can be cavitated without exciting other microbubbles, resulting in local sonoporation. The resolution of phase‐based positioning and frequency‐based transportation are 8.3 and 7.0 µm with 45° and 10 kHz settings, respectively.

Impact of the acoustic transmission path on the vibro-acoustic performance of sandwich panels with structural cores with bandgap behavior

In the search for lightweight and compact structures with favorable vibro-acoustic performance, periodic structures such as phononic crystals and locally resonant metamaterials have shown potential.Recently, these periodic structures are included between two panels in a sandwich configuration to combine the interesting vibro-acoustic performance of the core with the potential load-carrying capacity of the sandwich configuration.During the design and numerical analysis of the vibro-acoustic performance of these structures, commonly only the structural connection between the plates is considered.However, next to the structural connection, also an acoustic transmission path is present between the plates of the sandwich configuration in reality.Because of this, the promising performance due to the structural decoupling of the double panel configuration by the bandgap behavior of the periodic core predicted with the analyses only considering the structural connection, are often not attained in experimental measurements.In this work, the impact of the ignored acoustic transmission path on the sound transmission loss of sandwich panels with structural periodic cores which exhibit bandgap behavior, is investigated.It is shown that the sound transmission follows the path of least resistance.Therefore, it is crucial to consider both the structural as the acoustic path in the partitions during the design phase to correctly predict the vibro-acoustic performance of these novel sandwich panel configurations.

Continuous streamflow monitoring in shared watersheds using advanced underwater acoustic tomography system: a case study on Zayanderud River.

Iran has experienced a severe drought during the past two decades. Increasing water demand and decreasing available water resources have led the country to critical conflicts, particularly in shared watersheds. In these basins, the precise measurement of releasing water from upstream to downstream can be a key data for resolving water conflicts. The Iranian Ministry of Energy (MOE) makes the streamflow measurements through regional water administrative offices, mainly using the classical rating curve (RC) method. The documented measurements of runoff by adjacent offices usually present different estimations of the water resources, due to high uncertainties of the RC approach. Fluvial acoustic tomography (FAT) is a reliable technology for continuously monitoring streamflow, which can be implemented to solve this problem of shared basins. In this study, FAT is applied to the Zayanderud basin, an Iranian shared watershed and its results are compared with the RC methods. The main terms of FAT streamflow measurement uncertainty are velocity resolution component, and the selected flow angle between the stream direction and acoustic transmission path. Therefore, a new equation is proposed to carefully choose accurate angles for different river widths to decrease FAT measurement error in this paper. The obtained results show that the measured streamflow by FAT and RC are 9.89 m3/s and 10.3 m3/s, respectively, and the largest possible error of FAT is less than 15%.

Influence of Top Shape on Noise Reduction Effect of High-Speed Railway Noise Barrier

The top shape of the noise barrier mainly affects the acoustic diffraction, scattering and interference, changes the acoustic transmission path, increases the number and difficulty of diffraction, and thus reduces the field noise. This paper investigates the structural parameters of T-shaped and Y-shaped noise barriers at the top, analyses the noise reduction effect of different structural noise barriers by empirical formula method, and draws a conclusion with universal reference value, which provides a reference for the selection of noise barrier and noise control of high-speed railways in China.

Contributions of various transmission paths to speech privacy of open ceiling meeting rooms in open-plan offices

Installing open ceiling meeting rooms inside a large open-plan office provides a solution to increase speech privacy and to reduce speech disturbance in the office. The open ceiling meeting rooms have advantages of low cost construction and flexibility, but have lower speech privacy than that of enclosed rooms due to the open ceiling. Existing research shows that many factors should be taken into account to achieve good speech privacy in open-plan offices and improving only one of these factors may result in little improvement, so it is important to distinguish contributions of different acoustic transmission paths of open ceiling meeting rooms in open-plan offices. This paper proposes an impulse response separation method to quantify contributions of various acoustic paths of open ceiling rooms on speech privacy in open-plan offices. The method is verified with simulations based on the Odeon software and the experiments carried out in 3 different types of rooms. Finally, the proposed method is applied to the Fabpod, a semi enclosed meeting room located in a large indoor office at the Design Research Institute of the RMIT University, to obtain the contributions of different acoustic transmission paths to its speech privacy. The method proposed in this paper and the knowledge obtained are useful for architects to improve the acoustic performance of the next generation Fabpods which are now under design at RMIT University.

On the modeling of sound transmission through a mixed separation of flexible structure with an aperture.

Modeling sound transmission among acoustic media through mixed separations, consisting of both rigid/flexible structures with apertures, is a challenging task. The coexistence of both structural and acoustic transmission paths through the same coupling surface adds system complexities, hampering the use of existing sub-structuring modeling techniques when the system configuration becomes complex. In the present work, a virtual panel treatment is proposed to model thin apertures involved in such complex vibroacoustic systems. The proposed virtual panel considers an aperture as an equivalent structural component, which can be integrated with the solid/flexible structure to form a unified compound interface. This allows handling the entire compound interface as a pure structural element, thus providing an efficient and versatile tool to tackle system complexities when using sub-structuring techniques. The accuracy and convergence of the method are investigated and validated, and the effective thickness range allowing for the virtual panel treatments is determined. The capability and the flexibility of the proposed formulation are demonstrated through several numerical examples, with underlying physics being explored.

A perspective of modeling internal wave/acoustic wave interactions at the Naval Research Laboratory 1992-2012

Interest in modeling internal gravity waves in littoral regions was stimulated by the discovery of anomalous transmission loss in the Yellow Sea, predicted by Zhou and Rogers in 1991 to be caused by solitary wave propagation along the acoustic transmission path. Over the past 20 years, we have been modeling acoustic wave/solitary internal wave interactions and an overview and perspective of some of this work, illustrated by examples, will be presented. The relationship between internal waves and the scintillation index, horizontal refraction of acoustic energy, oceanographic waveguide focusing, mode coupling between acoustic and internal wave modes, and the effect of internal waves on acoustic field uncertainty are discussed. Some thoughts on the future of 4-D simulation of acoustic/internal wave interactions and modeling in the context of incomplete environmental knowledge are considered. [Work supported by the Office of Naval Research.]

Theoretical Studies on Ultrasound Induced Hall Voltage and Its Application in Hall Effect Imaging

Based on the principles of the Hall effect for ultrasound excitation and wave propagation in a static magnetic field, the theory of ultrasound induced Hall voltage generation is derived in explicit formulae with consideration of the acoustic radiation for a planar transducer. It is proved by numerical simulations that the induced Hall voltage is mainly generated at the conductivity boundary and can be used to map the spatial variation of the conductivity value along the acoustic transmission path. Both the simulated Hall voltage and the reconstructed image show good agreement with the experimental results of Wen [Ultrasonic Imaging 20 (1998) 206, 21 (1999) 186]. The promising simulation results suggest the potential of implementing medical electrical impedance imaging by means of ultrasound induced Hall effect imaging.

Civil aircraft cabin noise resource acoustic characteristic and transmission path analysis

Typically, there are mainly 4 different noise resources critical to cabin +F1184noise: auxiliary power unit (APU) noise, environment control system (ECS) noise, engine noise and turbulent boundary layer (TBL) noise. Because of the different acoustic characteristic and transmission path for each resource, their impacts to cabin noise level are not the similar. A vibration and noise test under ground and flight status of an in-service civil aircraft was conducted. Based on the test results, comparing the data under different test status, the acoustic characteristic and transmission path are analyzed for the 4 noise resources in this paper, including distribution characteristic, spectrum characteristic and transmission path. APU noise mainly affects the rear fuselage, ECS noise transmits by ducts, engine noise and TBL noise transmit through side panel.

Three dimensional parabolic equation modeling of acoustic intensity fluctuations due to internal wave phenomena.

During the Shallow Water 2006 (SW06) experiment, a J-15 acoustic source deployed from the Research Vessel Sharp transmitted broadband (50–450 Hz) chirp signals 15 km away from a vertical line array. The array was intentionally positioned near the shelf-break front and in an area where internal waves are known to occur. During the same time an internal wave, labeled event 44, passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both two and three dimensional) interference patterns. This presentation compares three dimensional modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship-born sensors to mimic the measured internal wave event. A modified version of the three dimensional Monterey–Miami parabolic equation (MMPE) code, which incorporates a user-defined sound speed field, is used. Measured and modeled intensity fluctuations are compared during dominating horizontal regimes such as refraction, focusing, and defocusing. Modal-dependent time-arrival analysis during the different horizontal regimes is examined. A sensitivity study of different sea-bottom properties is explored. [Work sponsored by the Office of Naval Research.]

Intensity fluctuations dominated by horizontal refraction during a strong nonlinear internal wave event.

During the Shallow Water 2006 (SW06) experiment, a J‐15 acoustic source deployed from the Research Vessel Sharp transmitted broadband (100–500 Hz) chirp signals 15 km away from a vertical line array. The array was intentionally positioned near the shelf‐break front and in an area where internal waves are known to occur. During the same time an internal wave, “Event 44,” passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both 2‐ and 3‐D) interference patterns. This presentation compares 3‐D modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship‐born sensors to mimic the measured internal wave event. A modified version of the 3‐D Monterey‐Miami parabolic equation (MMPE) code which incorporates a user‐defined sound s...

Three dimensional parabolic equation modeling of an internal wave event during Shallow Water 2006.

During the Shallow Water 2006 (SW06) experiment, a J‐15 acoustic source deployed from the Research Vessel Sharp transmitted broadband (100–500 Hz) chirp signals 15 km away from a vertical line array. The array was intentionally positioned near the shelf‐break front and in an area where internal waves are known to occur. During the same time an internal wave, “Event 44,” passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both two and three dimensional) interference patterns. Of specific interest are fluctuations of measured intensity preceding the internal wave’s arrival. Additionally, depth variability of the measured acoustic intensities can be attributed to a warm water intrusion coinciding with the internal wave event. This presentation shows recent modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship‐born sensors. A new version of the three‐dimensional Monterey–Miami parabolic equation code, which incorporates a user‐defined sound speed field, is used. [Work sponsored by the Office of Naval Research.]

Modeling intensity fluctuations of acoustic transmissions from the Research Vessel Sharp during Shallow Water 2006.

During the Shallow Water 2006 (SW06) experiment, a J-15 source deployed from the University of Delaware’s R/V Sharp transmitted various acoustic signals at several different bearings and ranges to the Woods Hole Oceanographic Institution’s vertical hydrophone line array. The array was intentionally positioned near the shelf-break front and in an area where internal waves are known to occur. During several of the R/V Sharp’s acoustic transmissions, internal waves passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both two and three dimensional) interference patterns. This presentation provides an overview of the R/V Sharp’s transmissions and the corresponding intensity fluctuations of received signals at the array. In order to model the intensity fluctuations, a sound speed field is reconstructed using data from environmental sensors such as acoustic Doppler current profilers, ship radar, conductivity-temperature-depth profiles, environmental moorings, and satellite images. Measured data are compared to a simulated sound field computed by a three dimensional acoustic propagation model. [Work sponsored by the Office of Naval Research.]

Propagation of impulsive broadband signals in a coastal ocean setting during the 1996 Shelfbreak Primer experiment

The 1996 Shelfbreak PRIMER experiment provided an opportunity to study the impulse response of a coastal ocean waveguide using broadband acoustic signals from explosive sources. Acoustic transmission paths in the vicinity of the shelfbreak included various orientations ranging from up‐slope to along‐slope, including interactions with a shelfbreak front. Acoustic receptions were acquired with a 16‐element vertical line array (VLA). In addition, thermistor string data acquired at the receiving array suggest that a group of high‐amplitude, internal waves traversed the test site during this portion of the experiment. Modal decomposition of broadband signal arrivals was performed to investigate variation of the impulse response during source deployments. Variations in the received spectra of individual normal modes were compared with numerical predictions for impulsive broadband signals propagating in range‐dependent environments constructed using oceanographic data available for the test site. The potential for mode coupling and three‐dimensional effects to shape the modal and spectral distribution of received energy is being investigated. Numerical and experimental results will be discussed. [Work supported by Office of Naval Research.]

The identification of tyre induced vehicle interior noise

Sound transmission into a vehicle is classified as either airborne or structure borne sound. From the point view of noise control, the reduction of noise transferred by different paths requires different solutions. Coherence function analysis is often used to identify transmission paths. However it can be difficult to separate the airborne from structure borne components. The principle of acoustic reciprocity offers a convenient method for overcoming this difficulty. The principal states that the transfer function between an acoustic volume velocity source and an acoustic receiver is independent of a reversal of the position of source and receiver. The work done on this study involves exciting a stationary tyre and measuring the surface velocity of the tyre at a number of discrete points. The acoustic transfer functions between each point on the tyre and a receiver point are measured reciprocally. Two sets of measurements are then combined to yield a measure of the sound pressure due to a point force on the tyre via the acoustic transmission path only. This technique also provides information on the relative contributions of various regions of the tyre wall to the resultant noise. Also the sound radiation characteristics, the horn effect, and resonance at the wheel housing are identified through the reciprocal measurement.

Spectral quality of acoustic predictions obtained by the ray method in coupled two-dimensional damped cavities

Numerical modelling of coupling in acoustics in the medium-frequency range poses problems, which remain to be solved. Indeed, in such cases, finite element methods in volumes or on boundaries generate too large a number of degrees of freedom due to the size of the domains (the volumes or the boundaries). With the ray method in simple convex damped cavities, it is possible to target a small number of points inside the domain and, subsequently, to economize on calculation time, making it possible to look for spectral instead of harmonic results. Does this still hold when damped cavities are coupled by an acoustic transmission path or by a vibrating structure, with aural perception in view? In fact, due to inherent approximations, the ray method is inaccurate in the presence of absorbent walls and thus in damped coupled cavities. However, an analysis will show that a hierarchy exists among the errors arising from the rays, and finally it will appear that only the grazing rays must be replaced by another approximation. In these conditions, the ray method is capable of solving coupling problems in acoustics in the medium-frequency range with greater computing speed than finite element methods.

Speech intelligibility in Grady Gammage Memorial Auditorium

‘‘The most important function of sound in theater is to ensure audience comfort in perceiving audio component of a performance’’ [Bracewell, Sound Design of Theater (1993)]. Background research has unveiled poor speech intelligibility at the Gammage Auditorium. This study aims to map speech intelligibility in different seating areas and measure the factors causing poor speech intelligibility. The instrument used to collect data will be the Techron TEF System 12 analyzer. This instrument uses modulation transfer function (MTF) and speech transmission index (STI) techniques. This is based on RASTI techniques by measuring the reduction of signal modulation in an acoustic transmission path [Keele, Jr. (1988)]. MTF is a measure of how well the amplitude modulation of a signal is preserved when a signal is sent from one point to another. The measurement modulations at different frequencies are converted to a single value that indicates the speech intelligibility in the auditorium. This single value is STI. Measurements are also provided on data for signal-to-noise ratio and RT60. A separate measurement of background noise level would indicate poor speech intelligibility due to excessive reverberation or background noise.

Acoustic Emission Source and Transmission Path Characterization Through Homomorphic Processing

Acoustic emission (AE) has been chosen as a means of monitoring cutting system changes from remote sensor locations. The determination of a processing strategy which can remove signal transmission path variability has been explored. This strategy, termed homomorphic processing, is developed and tested on both simulated and experimentally collected data. The recovery properties of this strategy are analyzed in terms of both AE source characterization and signal path transmission effects. These properties are found to be influenced by the choice of homomorphic lifter cutoff time. Guidelines are given for the selection of this parameter. Spectral representations of the recovered AE source show that signatures collected at remote sensor locations can be successfully used to identify process and structural changes in the cutting system.

Experimental verification of real‐valued orthogonal PN sequence applied to pulse compression sonar

AbstractIn the pulse compression sonar, the code with a sharp autocorrelation function is used as in spread spectrum communication, and they share many common technologies. In this paper, the real‐valued orthogonal pseudo‐noise (PN) sequence that can be used in both over a broad frequency range including dc is applied to the pulse compression sonar. By adapting digital correlation processing, a high performance close to the theory has been obtained. The codes are generated from a binary orthogonal PN sequence with a length of 127 and a multivalue orthogonal PN sequence with a length of 256 and are sent into an acoustic transmission path at a frequency of about 40 kHz. The correlation operation of the received code and the transmitted code is carried out on a personal computer. The multiple echo is detected at a low noise while the Gaussian noise and the locked sinusoidal wave can be suppressed with a processing gain close to the one predicted by the theory.