Acoustic Delay Research Articles

Sensitivity of sound speed fluctuation on acoustic arrival delay of middle range in deep water

For middle range acoustic propagation in deep water, there exists mainly four types of ray arrivals, namely direct path arrival, one time surface-reflected (SR) arrival, one time bottom-reflected (BR) arrival and one time surface-reflected bottom-reflected (SRBR) arrival. With Bellhop ray model, sensitivity of sound speed fluctuation on the arrival delay of middle range in deep water was studied. Argo profiles in Philippine Sea were used to establish the Sound Speed Profile (SSP) fluctuation set with the Empirical Orthogonal Function (EOF) method. Numerical simulation suggests that when the source was closer to the sea surface, the relative delay structure was more sensitive to the SSP fluctuation, and that the SR arrival and the SRBR arrival were more sensitive to the fluctuation than the BR arrival. When receiver range increases from 20 km to 30 km, sensitivities of ray arrivals gradually increase. Acoustic arrival delay data in the Philippine Sea experiment was used to invert the SSP. The inverted result agrees with the measured data well, suggesting the arrival structure was a nice choice for acoustic tomography of middle range in deep water.

Emulation Techniques for Small Scale Fading Aspects by Using Reverberation Chamber

Reverberation chambers (RVCs) are used to provide an efficient and reliable testbed for emulating the wireless channel effects in the laboratory environment. In the literature, various techniques have been studied to enrich the channel emulation capabilities of RVCs. However, insufficient control of some of the emulated channel characteristics (such as time and frequency dispersions) still leaves an open problem for RVC-based channel emulators. In this paper, novel channel emulation techniques by using RVC are introduced to enhance the flexibility in controlling the emulated time and frequency dispersions of the channels. Surface acoustic wave delay lines and power controllers (i.e., amplifiers and attenuators) are used to add degrees of freedom for manipulating the power delay profile during delay spread emulation. This technique also overcomes the challenge of achieving higher delay spread values with benchtop-sized RVC. The second technique is aimed to control the Doppler spectrum shape emulated in the chamber by judiciously placing radio frequency absorbers around the mechanical stirrer. Experimental and mathematical analyses are conducted to evaluate the proposed techniques, and the results show that the proposed methods can improve the channel emulation in the RVCs.

Passive Radar Delay and Angle of Arrival Measurements of Multiple Acoustic Delay Lines Used as Passive Sensors

After introducing noise radar probing of acoustic delay lines used as passive tags and sensors, we demonstrate the use of non-cooperative radiofrequency signal sources for such purposes in the context of passive radar measurement. A practical demonstration using IEEE 802.11n (WiFi) is given for a sensor operating at 2.42 GHz, solving the regulatory certification issue met when deploying dedicated radiofrequency emitters for short range radar applications. Furthermore, synthetic aperture radar measurement is completed by replacing the single surveillance antenna with a linear uniform array, solving the sensor collision issue when multiple targets are within range of the radar system.

Acoustic Detection of Submicron Depth of Ablation Crater Formed on the Metal Surface under Nanosecond Laser Irradiation

The recently published experimental data on the acoustic monitoring of the impact of a train of picosecond laser pulses with a total duration of about 500 ns and energy density up to 2 J cm−2 on a metal have been analyzed. During monitoring, the behavior of the acoustic signal delay τn with respect to the laser signal has been recorded. A comparison of the average acoustic delay τ0 for successive laser trains directed to the same target point (with a train-to-train interval of 30 s) shows a small variation in τ0 (< 0.1 ns), which is indicative of weak effect of ablation on the behavior of τn during a laser train. Under the conditions of additional laser irradiation in the intervals between trains, acoustic delay measurements demonstrate an increase in the average delay τ0 for subsequent trains, which may be related to the metal surface ablation caused by the additional irradiation.

Development of technology for producing nanowires on LiNbO3 piezoelectric plate surface

Integration of nanostructures with acoustic delay lines within planar technologies give the chance of development the acoustonanoelectronic sensors with high sensitivity and selectivity. An initial step in this direction is investigation of interaction of tunnel nanostructures with acoustic piezoactive waves propagating in piezoelectric substrates. In this work the technology of nanowire production on the surface of lithium niobate plate has been developed. This technology is based on using electronic lithography method with help an electronic beam in a raster electronic microscope. The nanostructure consisting of nanowire with size 20nm x 180nm was placed in the center between IDTs of acoustic delay line. The volt-ampere characteristics of this nanowire in presence and at the absence of the acoustic wave were meazured by picoampermeter. The analysis has shown that presence of piezoactive acoustic wave is influenced on electric current in a nanowire.

Development of electrode structure for acoustic delay lines by using inject printing method

The results concerning to study of possibility to produce electrode structure of acoustic delay lines by using inject printing method are presented. The investigation of morphologic and structure characteristics of electrode structure produced has been carried out. The possibility of excitation of plate acoustic waves characterized by high value of electro-mechanical coupling coefficient by such acoustic delay lines has been demonstrated.

An Acousto-Electric Nanobiosensor

A technology is developed that uses two multiscale structures on a single crystal piezoelectric substrate of lithium niobate. A system of counter-pin electrodes for an acoustic delay line operating in the 2–3 MHz range is formed via photolithography. The system is combined with nanotransducers 60–80 nm in size, produced by means of negative electron-beam nanolithography.

Frequency and time domain analysis of surface acoustic wave propagation on a piezoelectric gallium arsenide substrate: A computational insight

A computational study of the electromechanical response of micro-structure engineered two port surface acoustic wave delay lines on gallium arsenide is presented. The influence on the results of geometrical, material, and mesh parameters is also discussed. Furthermore, experimental results are provided to validate the numerical study. The device consists of two interdigital transducers composed of 40, 80, and 120 pairs of electrodes, respectively, with a pitch [Formula: see text] and distant [Formula: see text]. In particular, a microwave burst of surface acoustic waves propagating on gallium arsenide is fully characterized including multiple transit effects. These results are of major interest for understanding the dynamical behavior of complex systems such as surface acoustic wave–based sensors or energy harvesting devices at the nano and microscale.

A photoacoustic sensing probe using optical fiber acoustic delay line

In this paper, we report a new photoacoustic sensing probe design consisting of two optical fibers. One optical fiber is used for delivering the excitation light pulses. The other one serves as an acoustic delay line to relay the generated PA signal from the target to an outside ultrasound transducer. With the addition of suitable time delay, the original PA signal can be easily separated from the interference signals. To demonstrate this new design, a prototype probe was designed, fabricated and tested. The PA sensing performance was characterized with different concentration of black and red dye solutions. The testing results show that the PA sensing probe can provide good sensitivity and maintain high linearity over a wide range of concentrations. The detection of bovine blood embedded into chicken breast tissue was also conducted to demonstrate its potential usefulness for in-vivo applications.

Online monitoring of furnace exit gas temperature in power plants

Furnace exit gas temperature (FEGT) is an important physical parameter of energy conservation and environmental protection in a coal-fired boiler furnace; however, to date, there is no effective method for monitoring it continuously online. The recently developed acoustic pyrometry is a comparatively advanced method of temperature measurement which possesses the essential characteristics of traditional temperature measurement approaches. We experimentally implemented online FEGT monitoring using acoustic pyrometry, and we could successfully replace the flue gas temperature probes successfully. Two key problems of the acoustic pyrometry technique, i.e. the acoustic signal and time delay estimation, were solved. We adopted the linear sweeping frequency signal as a sound source signal; its sweeping frequency ranged from 500 to 4000 Hz and the sweeping cycle was 0.1 s. We used a generalized cross-correlation technique with PHAT (Phase Transformation) and ML (Maximum Likelihood) as the time delay estimation method when the boiler was in different states. The actual operation of the monitor indicated that the acoustic pyrometry system was accurate and reliable.

Effect of the conductivity of a thin film located near the acoustic delay line on the characteristics of propagating SH0 wave

The results of the study of the influence of the conductivity of a thin film located with a certain gap above the acoustic delay line on the characteristics of propagating acoustic wave with a quasi-shear-horizontal polarization (SH0) are presented. The delay line was made of Y-X lithium niobate plate with a thickness of 200 μm containing two interdigital transducers for exciting and receiving SH0 wave. The operating frequency range of the delay line was equal to 2.6–3.8 MHz. The 1 mm thick glass plate with a film of the given conductivity applied on one plate’s side was placed above this delay line with the some air gap. The change in the phase of output signal of the delay line was measured at the various values of the width of this gap. As films with the various values of the conductivity, tin dioxide films deposited on a glass plate by high-frequency reactive magnetron sputtering in the oxygen-argon mixture were used. It has been shown that the velocity of SH0 wave propagating in the delay line under investigation depends on the film conductivity and the width of the gap between the delay line and conductive film. The dependences of the change in the SH0 wave velocity on a width of the gap between the surface of the delay line and conductive film were constructed, as well as on the film conductivity. The comparison of the experimental results with the theoretical data showed their good agreement.

Structured ultrasound microscopy

We present a form of acoustic microscopy, called Structured Ultrasound Microscopy (SUM). It creates a volumetric image by recording reflected echoes of ultrasound waves with a structured phase front using a moving single-element transducer and computational reconstruction. A priori knowledge of the acoustic field produced by the single element allows us to relate the received echoes to a 3D scatter map within the acoustic beam itself, leading to an isotropic resolution at all depths. An aberration mask in front of the acoustic element imposes the phase structure, broadening the beam and breaking the spatial coherence between different voxels at equal acoustic propagation delay, increasing the uniqueness of the reconstruction. By translating the transducer across the 3D volume, we synthetically enlarge the imaging aperture by using multiple overlapping and spatially sparsely sampled measurements to solve for the entire image. In this paper, we explain the SUM technique and demonstrate microscopic imaging at 20 MHz of a 2.3 × 2.3 × 1.2 mm object in water, with an isotropic resolution below 100 μm. The proposed approach allows for wide-field 3D imaging at isotropic microscopic resolution using a small unfocused ultrasound sensor and multiple spatially sparsely sampled measurements. This technique may find applications in many other fields where space is constrained, device simplicity is desired, and wide-field isotropic high-resolution imaging is required.

Mobile Sinks Assisted Geographic and Opportunistic Routing Based Interference Avoidance for Underwater Wireless Sensor Network.

The distinctive features of acoustic communication channel-like high propagation delay, multi-path fading, quick attenuation of acoustic signal, etc. limit the utilization of underwater wireless sensor networks (UWSNs). The immutable selection of forwarder node leads to dramatic death of node resulting in imbalanced energy depletion and void hole creation. To reduce the probability of void occurrence and imbalance energy dissipation, in this paper, we propose mobility assisted geo-opportunistic routing paradigm based on interference avoidance for UWSNs. The network volume is divided into logical small cubes to reduce the interference and to make more informed routing decisions for efficient energy consumption. Additionally, an optimal number of forwarder nodes is elected from each cube based on its proximity with respect to the destination to avoid void occurrence. Moreover, the data packets are recovered from void regions with the help of mobile sinks which also reduce the data traffic on intermediate nodes. Extensive simulations are performed to verify that our proposed work maximizes the network lifetime and packet delivery ratio.

Mass, height of burst, and source-receiver distance constraints on the acoustic coda phase delay method.

This research uses the acoustic coda phase delay method to estimate relative changes in air temperature between explosions with varying event masses and heights of burst. It also places a bound on source-receiver distance for the method. Previous studies used events with different shapes, height of bursts, and masses and recorded the acoustic codas at source-receiver distances less than 1 km. This research further explores the method using explosions that differ in mass (by up to an order of magnitude) and are placed at varying heights. Source-receiver distances also cover an area out to 7 km. Relative air temperature change estimates are compared to complementary meteorological observations. Results show that two explosions that differ by an order of magnitude cannot be used with this method because their propagation times in the near field and their fundamental frequencies are different. These differences are expressed as inaccuracies in the relative air temperature change estimates. An order of magnitude difference in mass is also shown to bias estimates higher. Small differences in height of burst do not affect the accuracy of the method. An upper bound of 1 km on source-receiver distance is provided based on the standard deviation characteristics of the estimates.

Polar Cooperative Navigation Algorithm for Multi-Unmanned Underwater Vehicles Considering Communication Delays.

To solve the navigation accuracy problems of multi-Unmanned Underwater Vehicles (multi-UUVs) in the polar region, a polar cooperative navigation algorithm for multi-UUVs considering communication delays is proposed in this paper. UUVs are important pieces of equipment in ocean engineering for marine development. For UUVs to complete missions, precise navigation is necessary. It is difficult for UUVs to establish true headings because of the rapid convergence of Earth meridians and the severe polar environment. Based on the polar grid navigation algorithm, UUV navigation in the polar region can be accomplished with the Strapdown Inertial Navigation System (SINS) in the grid frame. To save costs, a leader-follower type of system is introduced in this paper. The leader UUV helps the follower UUVs to achieve high navigation accuracy. Follower UUVs correct their own states based on the information sent by the leader UUV and the relative position measured by ultra-short baseline (USBL) acoustic positioning. The underwater acoustic communication delay is quantized by the model. In this paper, considering underwater acoustic communication delay, the conventional adaptive Kalman filter (AKF) is modified to adapt to polar cooperative navigation. The results demonstrate that the polar cooperative navigation algorithm for multi-UUVs that considers communication delays can effectively navigate the sailing of multi-UUVs in the polar region.

Topological Acoustic Delay Line

Acoustic analogues of electronic topological insulators allow a wealth of opportunities for manipulating sound with unconventional acoustic edge modes that are immune to backscattering. However, acoustic devices based on topological edge states still lag, due to a lack of tunability and adaptability to functional needs. This study proposes a path to remote control and structural improvement, to achieve broadband, reconfigurable topological systems. In particular, it takes advantage of reflection-free sound propagation to engineer robust phase-delay detours. This approach could be used in various functions, including signal buffering and pulse processing.

Improved the Network Lifetime Through Energy Balancing in Depth Based Routing Protocol for Underwater Sensor Network

Underwater Wireless Sensor Network (UWSN) is a three-dimensional wireless sensor network which works under water and used acoustic signals for transmission. In underwater communication, energy efficiency in routing is play a vital role due to the distinctive characteristics, such as water currents, limited battery power, and long acoustic propagation delay. Due to the water undercurrents sensor nodes moves uninterruptedly and makes dynamic and complex network topology. Depth-based routing protocol (DBR) is much usable protocol in underwater scenario, because it uses only depth information only which is easier to obtain. However, in DBR, packets may be forwarded through multiple paths and some sensor nodes are frequently used to transmit data which is nearer to the surface sink, might cause energy waste as well as moderate the life of network. In this article, we propose an energy balancing scheme for DBR to provide energy efficient routing and to increase the life of network.

Energy decay of variable-coefficient wave equation with acoustic boundary conditions and delay

ABSTRACTIn this paper, we consider a variable-coefficient wave equation with memory type acoustic boundary conditions and a constant time delay in the boundary feedback. Using the Riemannian geometry method, we prove the exponential decay of the system with memory type acoustic boundary conditions and a constant time delay under some suitable assumptions.

High-transmission acoustic self-focusing and directional cloaking in a graded perforated metal slab

A design strategy and its modeling for high-transmission acoustic self-focusing and directional cloaking in a two-dimensional (2D) and an axisymmetric three-dimensional (3D) gradient-index phononic crystal (GRIN-PC) are reported in this paper. A gradient perforated aluminum slab sandwiched by water is considered. A low-loss directional cloaking device is achieved by controlling the matching coefficient between the slab and the water. The anisotropy coefficient that affects the scattering properties is also introduced. Furthermore, the phase discontinuity for directional cloaking inside and outside the slab is overcome by introducing a non-gradient slab having a lower group velocity behind the GRIN slab as an acoustic delay device. In addition, an axisymmetric 3D directional cloaking structure is obtained by rotating the corresponding 2D structure around the slab axis.

Development of wireless, chipless neural stimulator by using one-port surface acoustic wave delay line and diode–capacitor interface

For the first time, a wireless and chipless neuron stimulator was developed by utilizing a surface acoustic wave (SAW) delay line, a diode–capacitor interface, a sharp metal tip, and antennas for the stimulation of neurons in the brain. The SAW delay line supersedes presently existing complex wireless transmission systems composed of a few thousands of transistors, enabling the fabrication of wireless and chipless transceiver systems. The diode–capacitor interface was used to convert AC signals to DC signals and induce stimulus pulses at a sharp metal probe. A 400 MHz RF energy was wirelessly radiated from antennas and then stimulation pulses were observed at a sharp gold probe. A ∼5 m reading distance was obtained using a 1 mW power from a network analyzer. The cycles of electromagnetic (EM) radiation from an antenna were controlled by shielding the antenna with an EM absorber. Stimulation pulses with different amplitudes and durations were successfully observed at the probe. The obtained pulses were ∼0.08 mV in amplitude and 3–10 Hz in frequency. Coupling-of-mode (COM) and SPICE modeling simulations were also used to determine the optimal structural parameters for SAW delay line and the values of passive elements. On the basis of the extracted parameters, the entire system was experimentally implemented and characterized.