Wave Path Research Articles

A reliable velocity estimation in a complex deep-water environment using downward continued long offset multi-channel seismic (MCS) data

The estimation of a reliable velocity–depth model from towed streamer marine seismic data recorded in deep water, especially with a complex seafloor environment, is challenging. The determination of interval velocities from the normal move-out (NMO) of the reflected seismic signals for shallow reflectors (<1 km below the seafloor) is compromised by the combination of a long wave path in the water column and the complex ray paths due to topography, leading to small move-out differences between reflectors. Furthermore, low sediment velocities and deep water produce refraction arrivals only at limited far offsets that contain information about deeper structures. Here, we present an innovative method where towed streamer seismic data are downward continued to the seafloor leading to the collapse of the seafloor reflection and the emergence of refraction events as first arrivals close to zero offset, which are used to determine a high-resolution near surface velocity–depth model using an efficient tomographic method. These velocities are then used to perform pre-stack depth migration. We found that the velocity–depth model derived from tomography of downward continued towed streamer data provides a far superior pre-stack depth migrated image than those produced from velocity–depth models derived from conventional velocity estimation techniques.

Monopulse instantaneous 3D imaging for wideband radar system

To avoid the complicated motion compensation in interferometric inverse synthetic aperture (InISAR) and achieve realtime three-dimensional (3D) imaging, a novel approach for 3D imaging of the target only using a single echo is presented. This method is based on an isolated scatterer model assumption, thus the scatterers in the beam can be extracted individually. The radial range of each scatterer is estimated by the maximal likelihood estimation. Then, the horizontal and vertical wave path difference is derived by using the phase comparison technology for each scatterer, respectively. Finally, by utilizing the relationship among the 3D coordinates, the radial range, the horizontal and vertical wave path difference, the 3D image of the target can be reconstructed. The reconstructed image is free from the limitation in InISAR that the image plane depends on the target's own motions and on its relative position with respect to the radar. Furthermore, a phase ambiguity resolution method is adopted to ensure the success of the 3D imaging when phase ambiguity occurs. It can be noted that the proposed phase ambiguity resolution method only uses one antenna pair and does not require a priori knowledge, whereas the existing phase ambiguity methods may require two or more antenna pairs or a priori knowledge for phase unwarping. To evaluate the performance of the proposed method, the theoretical analyses on estimation accuracy are presented and the simulations in various scenarios are also carried out.

Broadband Frequency and Spatial On-Demand Tailoring of Topological Wave Propagation Harnessing Piezoelectric Metamaterials

Many engineering applications leverage metamaterials to achieve elastic wave control. To enhance the performance and expand the functionalities of elastic waveguides, the concepts of electronic transport in topological insulators have been applied to elastic metamaterials. Initial studies showed that topologically protected elastic wave transmission in mechanical metamaterials could be realized that is immune to backscattering and undesired localization in the presence of defects or disorder. Recent studies have developed tunable topological elastic metamaterials to maximize performance in the presence of varying external conditions, adapt to changing operating requirements, and enable new functionalities such as a programmable wave path. However, a challenge remains to achieve a tunable topological metamaterial that is comprehensively adaptable in both the frequency and spatial domains and is effective over a broad frequency bandwidth that includes a subwavelength regime. To advance the state of the art, this research presents a piezoelectric metamaterial with the capability to concurrently tailor the frequency, path, and mode shape of topological waves using resonant circuitry. In the research presented in this manuscript, the plane wave expansion method is used to detect a frequency tunable subwavelength Dirac point in the band structure of the periodic unit cell and discover an operating region over which topological wave propagation can exist. Dispersion analyses for a finite strip illuminate how circuit parameters can be utilized to adjust mode shapes corresponding to topological edge states. A further evaluation provides insight into how increased electromechanical coupling and lattice reconfiguration can be exploited to enhance the frequency range for topological wave propagation, increase achievable mode localization, and attain additional edge states. Topological guided wave propagation that is subwavelength in nature and adaptive in path, localization, and frequency is illustrated in numerical simulations of thin plate structures. Outcomes from the presented work indicate that the easily integrable and comprehensively tunable proposed metamaterial could be employed in applications requiring a multitude of functions over a broad frequency bandwidth.

Millimeter Wave Path Loss Modeling for 5G Communications Using Deep Learning With Dilated Convolution and Attention

An accurate and efficient path loss modeling method for millimeter wave communications plays a significant role in the large-scale deployment of a fifth-generation (5G) mobile communication system. Conventional path loss modeling methods such as deterministic methods, empirical methods, and machine learning-based methods, in practice, cannot achieve the desired level of performance in terms of accuracy. This paper proposes a novel path loss model for 5G communications in suburban scenarios using deep learning with dilated convolution and attention. Dilated convolution is used to alleviate the locality of feature extraction and capture the global information on input images. Attention rendered by global context blocks helps the attention-enhanced convolutional neural network (AE-CNN) model utilize the global information on inputs to extract essential features of propagation environments. A distance-embedded local area multi-scanning algorithm which generates input images that can improve learning the latent features with dependency on distance is proposed. The experimental results indicate that the AE-CNN model can outperform state-of-the-art deterministic and empirical methods in terms of root mean square error in test scenarios.

TECHNIQUE FOR ESTIMATING THE EFFICIENCY OF NOISE PROTECTIVE ACOUSTIC SCREENS IN THE PRESENCE OF FLAT ANTI-DIFFRACTORS

To increase the efficiency of acoustic screens when protecting against acoustic noise, anti-diffractors are used to reduce the diffraction level on the upper edge of the screen. The aim of the work is to refine the mathematical model used to assess noise protection efficiency with the help of an acoustic screen with an installed one-sided flat-type anti-diffractor. The well-known techniques based on the principle of the amplitude dependence of the sound wave intensity from two sources are analyzed: a point-type noise source and a secondary cylindrical wave source - the screen edge, on which the sound wave is diffracted. Taking into account that the change in the distance between the anti-diffractor and the working point in the acoustic shadow zone is associated with a change in the diffraction angle, it is proposed to evaluate the acoustic screen effectiveness by comparing the initial sound wave propagation paths. An approach to a mathematical calculation model formation is proposed, in which the diffraction point located at the intersection of two components of the wave path to the operating point is considered to be the location of the sound wave secondary source in the area of the screen upper edge: from the noise source to the flat-type anti-diffractor installed on the upper edge of the screen, and from the anti-diffractor rear edge to the operating point. Relationships that make it possible to solve the problem of analytical assessment of noise-protective acoustic screens' effectiveness when installing anti-diffractors on their upper face in the form of flat hinged panels oriented towards the acoustic shadow are obtained.

Obstruction-invariant occupant localization using footstep-induced structural vibrations

In this paper, we characterize the effects of obstructions on footstep-induced floor vibrations to enable obstruction-invariant indoor occupant localization. Occupant localization is important in smart building applications such as smart healthcare and energy management. Maintenance and installment requirements limit the application of current sensing approaches (e.g., mobile-based, RF-based, and pressure-based sensing) in real-life applications. To overcome these limitations, prior work has utilized footstep-induced structural vibrations for occupant localization. The main intuition behind these approaches is that the footstep-induced floor vibration waves take different amounts of time to arrive at different sensors. These Time-Differences-of-Arrival (TDoA) can then be leveraged to locate the footstep by assuming similar velocities between the footstep and various sensor locations. This assumption makes these approaches suitable for open areas; however, real buildings have various types of obstructions (e.g., walls, furniture, etc.) which affect wave propagation velocities and hence significantly reduce localization accuracy. Therefore, the prior work requires unobstructed paths between footsteps and sensors for accurate occupant localization, which increases the sensing density requirement and thus, instrumentation and maintenance costs. We have observed that the obstruction mass is one of the key factors in affecting the wave propagation velocity and reducing the localization accuracy. Therefore, to overcome the obstruction challenge, we localize footsteps by considering different velocities between the footsteps and sensors depending on the existence and mass of obstruction on the wave path. Specifically, we (1) detect and estimate the mass of the obstruction by characterizing the wave attenuation rate, (2) use this estimated mass to find the propagation velocities for localization by modeling the velocity-mass relationship through the lamb wave characteristics, and (3) introduce a non-isotropic multilateration approach which robustly leverages these propagation velocities to locate the footsteps (and the occupants). In field experiments, we achieved average localization error of 0.61 meters, which is (1) the same as the average localization error when there is no obstruction and (2) 1.6X improvement compared to the baseline approach.

Variations in Wave Energy and Amplitudes along the Energy Dispersion Paths of Nonstationary Barotropic Rossby Waves

The variations in the wave energy and the amplitude along the energy dispersion paths of the barotropic Rossby waves in zonally symmetric basic flow are studied by solving the wave energy equation, which expresses that the wave energy variability is determined by the divergence of the group velocity and the energy budget from the basic flow. The results suggest that both the wave energy and the amplitude of a leading wave increase significantly in the propagating region that is located south of the jet axis and enclosed by a southern critical line and a northern turning latitude. The leading wave gains the barotropic energy from the basic flow by eddy activities. The amplitude continuously climbs up a peak at the turning latitude due to increasing wave energy and enlarging horizontal scale (shrinking total wavenumber). Both the wave energy and the amplitude eventually decrease when the trailing wave continuously approaches southward to the critical line. The trailing wave decays and its energy is continuously absorbed by the basic flow. Furthermore, both the wave energy and the amplitude oscillate with a limited range in the propagating region that is located near the jet axis and enclosed by two turning latitudes. Both the leading and trailing waves neither develop nor decay significantly. The jet works as a waveguide to allow the waves to propagate a long distance.

Hybrid LPG-FBG Based High-Resolution Micro Bending Strain Sensor

Simple SummaryThe solved problem, the helical core sensor for spatial coordinate direction within the fiber was applied to monitor the microscopic repetitive pattern caused by the body structure on the body surface. The body motion state was measured using the strain change of the helical core in three-dimensional space For real-time monitoring, sophisticated sensing and stability against noise are required. The femtosecond laser processing allows us to check the measurement reliability of the sensor through the design of the long and short period gratings. This shows the possibility of monitoring spatial coordinates from one core to one core. It can be used as a wearable sensor.Sensitivity and reliability are essential factors for the practical implementation of a wearable sensor. This study explores the possibility of using a hybrid high-resolution Bragg grating sensor for achieving a fast response to dynamic, continuous motion and Bragg signal pattern monitoring measurement. The wavelength shift pattern for real-time monitoring in picometer units was derived by using femtosecond laser Bragg grating processing on an optical wave path with long-period grating. The possibility of measuring the demodulation system’s Bragg signal pattern on the reflection spectrum of the femtosecond laser precision Bragg process and the long-period grating was confirmed. By demonstrating a practical method of wearing the sensor, the application of wearables was also explored. It is possible to present the applicability of sophisticated micro transformation measurement applications in picometer units.

High-Directivity Optimization Technique for Irregular Arrays Combined With Maximum Entropy Model

A high-directivity optimization technique for irregular arrays combined with maximum entropy model is presented. First, the major cause of the reduction in directivities of irregular arrays has been analyzed, namely, the so-called relative wave path difference. The larger size of subarrays and the wider scanning angle will inevitably enlarge relative wave path differences, thus resulting in the reduction of directivity. Aimed at this challenging issue, a mixed integer linear programming model is proposed to achieve high directivity and low sidelobe simultaneously for tetromino-shaped irregular arrays. An embedded structure algorithm has been applied to efficiently optimize a large-scale array with 2-D 60° maximum scanning angles. Moreover, representative numerical examples based on Vivaldi finite arrays are presented to demonstrate the effectiveness of the proposed approach. Numerical results show that the directivity of an optimized array by the proposed method outperforms those of the reported state-of-the-art methods by about 1 dB for the scan to 45°.

The dynamics of 3-min wavefronts and their relation to sunspot magnetic fields.

We present a study of wave processes occurring in solar active region NOAA 11131 on 10 December 2010, captured by the Solar Dynamics Observatory in the 1600 Å, 304 Å and 171 Å channels. For spectral analysis, we employed pixelized wavelet filtering together with a developed digital technique based on empirical mode decomposition. We studied the ∼3-minute wave dynamics to obtain relationships with the magnetic structuring of the underlying sunspot. We found that during development of wave trains the motion path occurred along a preferential direction, and that the broadband wavefronts can be represented as a set of separate narrowband oscillation sources. These sources become visible as the waves pass through the umbral inhomogeneities caused by the differing magnetic field inclination angles. We found the spatial and frequency fragmentation of wavefronts, and deduced that the combination of narrowband spherical and linear parts of the wavefronts provide the observed spirality. Maps of the magnetic field inclination angles confirm this assumption. We detect the activation of umbral structures as the increasing of oscillations in the sources along the front ridge. Their temporal dynamics are associated with the occurrence of umbral flashes. Spatial localization of the sources is stable over time and depends on the oscillation period. We propose that these sources are the result of wave paths along the loops extending outwards from the magnetic bundles of the umbra. This article is part of the Theo Murphy meeting issue 'High-resolution wave dynamics in the lower solar atmosphere'.

Efficient 3-D velocity model building using joint inline and crossline plane-wave wave-equation migration velocity analyses

SUMMARY Wave-equation migration velocity analysis (WEMVA) is an image-domain inversion method for velocity model building. Automatic plane-wave WEMVA (PWEMVA) calculates the moveouts of plane-wave common-image gathers (CIGs) by searching a best-fitting parabola with semblance analysis and backprojects residual CIG moveouts into wavefield wave paths with a reflection tomographic kernel. However, 3-D PWEMVA is very computationally expensive because 3-D reflection tomographic inversion requires at least five 3-D reverse-time migrations per iteration and stores two types of source wavefields at model boundaries. We develop a joint inline and crossline PWEMVA method for efficient 3-D velocity model building. We alternatively implement the inline and crossline PWEMVAs with a constraint for each other, in which we iteratively construct the 3-D velocity model update through 1-D spline interpolation of 2-D gradients. The inline and crossline joint inversion is practical since PWEMVA only inverts for low-wavenumber velocity perturbations along wave paths, and the method can take less than 1 per cent of the computational cost of full 3-D PWEMVA. To construct unaliased plane waves for our joint inline and crossline PWEMVA, we develop a 3-D data interpolation method in the frequency–wavenumber (FK) domain to recover regularly and randomly missing traces. The method minimizes the misfit on sufficiently localized data subsets with iterative optimal step lengths and a gradient preconditioner that iteratively selects dominant dips along different azimuths. In numerical experiments, we use a 3-D synthetic seismic data set and a land 3-D field seismic data set acquired at the Farnsworth CO2-EOR (enhanced oil recovery) field to demonstrate the efficacy of our velocity model building and data interpolation methods.

Designing flat optical devices for path and wave vector manipulation by space transformation along a fixed direction

The capability of flat devices to manipulate the wave paths and wave vectors of electromagnetic waves is studied. The devices consisting in a transformed medium delimited by two parallel planes are designed by transforming the original free space along a fixed direction by an arbitrary function. We present the general equations describing the wave path and wave vector evolution inside such flat devices. In order to validate the theoretical results, a flat convergent lens working at oblique incidence is designed and discussed through computer simulations.

Non-local linear-response functions for thermal transport computed with equilibrium molecular-dynamics simulation

We establish an approach to compute linear-response functions to elucidate heat waves and non-local thermal transport. The theory is able to describe the response of a system to external heat sources that are nonuniform in space and time. The response functions are computed using equilibrium molecular-dynamics simulations of an Ar crystal modeled using the standard Lennard–Jones potential. It is shown that for low temperatures and short length scales, transport can be partially or even completely ballistic, with the response primarily limited by the group velocity of lattice waves. By contrast, at longer length scales and higher temperatures, the response functions correspond more closely to diffusive transport characteristic of Fourier’s law. It is also shown how the effective thermal conductivity can be determined in a partially ballistic regime. The results demonstrate the known reduction in the effective thermal conductivity observed when system dimensions are smaller than the mean-free path for lattice waves. Finally, we show how the determination of relevant response functions can be used to model heating of a crystal without requiring additional atomic-scale simulations. Differences between computed results and predictions from Fourier’s law represent wave-like, partially ballistic transport.

A holistic approach of numerical analysis of the geology effects on ground motion prediction: Argostoli site test

When assessing seismic risk at a city scale, local site conditions can significantly modify the destructive potential of an earthquake. This was the case in Mexico City in 1985 and 2017, which is located on a sedimentary valley. For that reason, characterization and consideration of these site effects, in addition to assessing the probability of occurrence of a destructive earthquake in a given region, are crucial. For this purpose, a tri-dimensional model was developed using a numerical code that permits to carry out such kind of studies. The code is based on the spectral element method allowing solving the waves propagation problem in tri-dimensional solid media. The seismic phenomenon is simulated in its entirety: from the seismic source to the site using a representative model of the complexity of the wave path. However, this introduces uncertainties that must be quantified, controlled and reduced by validating the results of the numerical tool with measurements on a real study site. This work aims to study numerically the effect of the geometric structure of soil and subsoil on the prediction of ground motion at the regional scale. The first obtained results show the importance of the in situ measures on the regional-scale simulations.

3D flower-like Co-based oxide composites with excellent wideband electromagnetic microwave absorption

Transition metal oxides because of their excellent dielectric properties have been population for electromagnetic wave absorption application. In this paper, through two-step synthesis, hollow CoSnO3 was in-situ growth between layers of self-assembled flower-like ZnCo2O4 in the solvothermal process. The multi-layer sheet structure of ZnCo2O4 nanoflowers provides growth space for CoSnO3, which can increase interface polarization and natural resonance. Hybrid structure expands the propagation path of electromagnetic waves and the times of reflections and scattering. By adjusting the content of the growing process of CoSnO3, the maximum reflection loss (RL) at 12.4 GHz was −56.0 dB, and the wide effective absorption bandwidth (EAB) of 6.24 GHz (RL < −10 dB) was obtained at a thin matching thickness of 2.6 mm ZnCo2O4@CoSnO3 composites showed satisfactory impedance matching in the frequency range of 2–18 GHz. Therefore, ZnCo2O4@CoSnO3 composites provides a new research idea for electromagnetic wave absorption in morphology designed.

Images of 3-D Maneuvering Motion Targets for Interferometric ISAR With 2-D Joint Sparse Reconstruction

In the actual scene of interferometric inverse synthetic aperture radar (InISAR) imaging, the noncooperative targets may make a nonuniform 3-D rotational motion (3-D-RM), which contributes not only to the time-variant Doppler modulation but also to the spatial-variant wave path difference (SVWPD). This, in turn, seriously degrades the 3-D geometry reconstruction accuracy of the targets. Furthermore, it is an enormous challenge to realize InISAR imaging from sparse frequency band and sparse aperture (SFB-SA) signals. This article seeks to address the problems of fine image registration and 2-D joint sparse reconstruction (2-D-JSR) for InISAR imaging with SFB-SA signals. With regard to the maneuvering targets with 3-D-RM, a novel SVWPD signal model is established. Moreover, a new algorithm, named joint wave path difference compensation (JWPDC) algorithm, is developed to perform fine image registration. It can not only combine multiple channels to achieve image registration but also jointly compensate for the non-SVWPD (NSVWPD) and SVWPD. A joint multichannel 2-D-JSR (JMC-2-D-JSR) ISAR imaging algorithm is also proposed according to the SFB-SA signal model to produce high-resolution ISAR images. Underpinned by the Bayesian compressive sensing (BCS) theory, the JMC-2-D-JSR ISAR imaging can be realized by solving a sparsity-driven optimization problem via a modified quasi-Newton solver. Through iterative processing of JMC-2-D-JSR and JWPDC, the high-quality 3-D InISAR images of maneuvering targets with 3-D-RM can be obtained. Extensive experimental results based on both simulated and real data corroborate the effectiveness of the proposed algorithm that outperforms other available InISAR imaging frameworks in 2-D imaging, 3-D imaging, and motion compensation.

Manipulation of low-frequency resonance scattering from submerged slightly deformed polymer cylinders

Backscattering enhancement associated with subsonic Rayleigh wave resonance of a polymethlmethacrylate (PMMA) cylinder is observed at low frequencies in water, which suggests that the PMMA cylinders may have essential applications in the low-frequency standard scatterer design. A slightly deformed surface structure with regular corrugation is presented to manipulate the low-frequency backscattering resonance frequency of PMMA cylinder passively. Using the perturbation method, the approximate resonance frequency shift is derived for an infinite slightly deformed cylinder with regular corrugations. Based on the phase matching of Rayleigh waves, the mechanism of low-frequency resonance frequency shift is revealed. Studies show that compared with a bare cylinder, a small boundary deformation can cause the propagation path of Rayleigh waves to change, namely, the Rayleigh waves propagate along the slightly deformed surface with regular corrugations. The modified propagation path can cause the propagation phase to change, which brings about the low-frequency backscattering resonance frequency shift of a PMMA cylinder. Furthermore, how the resonance frequency shifts with the deformation coefficient and period of the corrugation is discussed in detail. The backscattering resonance frequency of the regular corrugated cylinder shifts to low frequency with the increase of &lt;i&gt;ξ&lt;/i&gt; under the condition of the deformation coefficient &lt;i&gt;ξ&lt;/i&gt; &gt; 0, but shifts to high frequency with the decrease of &lt;i&gt;ξ&lt;/i&gt; at &lt;i&gt;ξ&lt;/i&gt; &lt; 0, and the resonance frequency shift increases with the increase of absolute value of deformation coefficient. When corrugation period &lt;i&gt;m&lt;/i&gt; &lt; 10, the phase variation with &lt;i&gt;m&lt;/i&gt; is too small, so the corrugation period has little effect on the resonance frequency shift. Finally, acoustic scattering experiment of the regular corrugated cylinder is conducted in the tank. The resonance frequency shift is obviously observed in the experiment, which is in good agreement with the theoretical prediction. Hence, the characteristics of backscattering enhancement associated with subsonic Rayleigh wave and the resonance frequency shifts make the PMMA deformed cylinder have potential applications such as in standard scatter design and identification using “AcoustiCode”.

Adaptive path following control for Wave gliders in time-varying environment

Path following control plays an essential role in improving accuracy of navigation and achieving a smooth motion control. However, the performance will exhibit large lateral errors caused by weak maneuverability, large time-lag, and large ocean current disturbance when the wave glider is gliding with a low and time-varying speed. An adaptive path following control integrated an adaptive line-of-sight (ALOS) algorithm and an improved artificial potential field (IAPF) algorithm was put forward in this paper, which could extremely guarantee path following accuracy. The adaptive control based a LOS was introduced to dynamically adjust a parameter of the LOS so that the output desired heading of the wave glider was on-time updated based on the velocity of the wave glider and path following error. The IAPF was applied to analyze and modify the output of the ALOS guiding the vehicle always convergent to the desired path, which could make a real time self-diagnosing, monitoring and correction in path following control. Following this, a closed-loop control was put forward with a dynamic model of the “Black Pearl” wave glider and the given path following control. The proposed control was verified by simulations and sea trials compared with conventional LOS, which demonstrated its effectiveness and long-term reliability.

Mapping Intrinsic and Scattering Attenuation in the Southern Aegean Crust Using S Wave Envelope Inversion and Sensitivity Kernels Derived From Perturbation Theory

AbstractWe applied sensitivity kernels based on perturbation theory to map the crustal intrinsic and scattering attenuation of S wave envelopes in the southern Aegean. The southern Aegean crust is under extension due to the rollback of the Nubian plate, which is subducting beneath the Aegean plate. The waveforms of 104,531 crustal events (&lt;40 km) were used to calculate S wave envelopes in four frequency bands. The S wave envelopes were modeled using the 3‐D isotropic solution of the radiative transfer equation with a factor for energy leakage. A two‐stage grid search with linear least squares was applied to estimate the attenuation parameters from each S wave envelope. Then we calculated the 2‐D scattering and absorption sensitivity kernels for each wave path based on perturbation theory. These kernels and the envelope attenuation parameters were inverted using the Markov chain Monte Carlo algorithm to obtain maps of intrinsic and scattering attenuation (Qi−1 and Qsc−1). High Qi−1 has thermal origin associated with fluids while high Qsc−1 stems from velocity contrasts caused by deformed structure such as faults, folds, or fractures. The Corinth rift, the Santorini‐Amorgos zone, and the Gulf of Gökova show strong extensional deformation, which may produce high Qsc−1. The deformed oceanic material accreted below the continental crust and fractures generated by large thrust earthquakes likely produce high Qsc−1 in Crete. The Corinth rift with its repeated earthquake swarms demonstrates fluid activity, which can explain high Qi−1. Thermal contrasts generated by metamorphic core complexes are a potential source of Qi−1 in Cyclades and Crete.

Does the “Reticular Lamina Nonlinearity” Contribute to the Basal DPOAE Source?

The spatial extent of the cochlear region that actually contributes to the DPOAE signal measured in the ear canal may be evaluated experimentally using interference tones or computed numerically using nonlinear cochlear models. A nonlinear transmission-line cochlear model is used in this study to evaluate whether the recently reported nonlinear behavior of the reticular lamina (RL) over a wide basal region may be associated with generation of a significant distortion product otoacoustic emission (DPOAE) component. A two-degrees-of-freedom 1-D nonlinear model was used as discussed by Sisto et al. (2019), in which each local element consists of two coupled oscillators, roughly representing the basilar membrane (BM) and the RL. In this model, the RL shows a strongly nonlinear response over a wide region basal to the characteristic place, whereas the BM response is linear outside the narrow peak region. Such a model may be considered as that using the minimal number of degrees of freedom necessary to separately predict the motion of the BM and RL, while preserving important cochlear symmetries, such as the zero-crossing invariance of the impulse response. In the numerical simulations, the RL nonlinearity generates indeed a large intracochlear distortion product source, extended down to very basal cochlear regions. Nevertheless, due to the weak and indirect coupling between the RL motion and the differential fluid pressure in the basal part of the traveling wave path, no significant contribution from this mechanism is predicted by the model to the generation of the DPOAE signal that is eventually measured in the ear canal.