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[EN]We demonstrate the complete temporal characterization of the optical waveform of visible near-infrared octave-spanning ultrashort laser pulses, using an all-optical, all-solidstate and fully inline dispersion-scan device based only on second-harmonic generation.

Motivated by recently published methods using frequency decompositions of convolutions (e.g. Octave Convolutions), we propose a novel convolution scheme to stabilize the training and reduce the likelihood of a mode collapse. The basic idea of our approach is to split convolutional filters into additive high and low frequency parts, while shifting weight updates from low to high during the training. Intuitively, this method forces GANs to learn low frequency coarse image structures before descending into fine (high frequency) details. We also show, that the use of the proposed soft octave convolutions reduces common artifacts in the frequency domain of generated images. Our approach is orthogonal and complementary to existing stabilization methods and can simply be plugged into any CNN based GAN architecture. Experiments on the CelebA dataset show the effectiveness of the proposed method.

Broadband filters with s harp roll-offs are essential f or flexibly handling optical signals in integrated photonic platforms. Here, recent developments on novel silicon photonic structures with octave-wide multiplexing capabilities will be reviewed.

Parametric nonlinear optical processes allow for the generation of new wavelengths of coherent electromagnetic radiation. Their ability to create radiation that is widely tunable in wavelength is particularly appealing, with applications ranging from spectroscopy to quantum information processing. Unfortunately, existing tunable parametric sources are marred by deficiencies that obstruct their widespread adoption. Here we show that ultrahigh-Q crystalline microresonators made of magnesium fluoride can overcome these limitations, enabling compact and power-efficient devices capable of generating clean and widely-tunable sidebands. We consider several different resonators with carefully engineered dispersion profiles, achieving hundreds of nanometers of sideband tunability in each device when driven with a standard low-power laser at 1550 nm. In addition to direct observations of discrete tunability over an entire optical octave from 1083 nm to 2670 nm, we record signatures of mid-infrared sidebands at almost 4000 nm. The simplicity of the devices considered -- compounded by their remarkable tunability -- paves the way for low-cost, widely-tunable sources of electromagnetic radiation., Comment: 10 pages, 4 figures, submitted 1st of November 2018

The article considers the technique and results of computational studies of the acoustic characteristics of the elements and the motor vehicle intake system. It describes the purpose and operation characteristics of the intake system. It is noted that the waves occurring in the intake tract, the nature of which depends on the geometry of the intake tract and the operating mode of the engine, determine the acoustic characteristics of the intake system and can improve or worsen the filling of the cylinders. Adding Helmholtz resonators to the manifolds improves the acoustic characteristics of the intake system depending on the engine speed and maximizes filling of cylinders for different speed modes. This allows to increase the power, economic, environmental performance of the engine and reduce the gas-dynamic noise emitted by the cutoff of the intake tract. A resonator was developed on the basis of finite element modeling to replace the connecting pipe of the air supply hose of hot air for improving the acoustic characteristics of motor vehicle intake system. The range of transmission loss (TL) of intake system has been calculated to evaluate the performance of the elements and the intake system in acoustical performance. The overall level of sound pressure at idling speed is determined by radiation in the frequency range 100–5000 Hz. In this range, in most one-third octave, the resonator lowers the sound pressure up to 5 dBA.

A dual-core photonic crystal fiber (DC-PCF) of hexagonal lattice is designed with a tailored dispersion profile possessing a large air-filling fraction. Numerical investigation of the PCF reveals a great potential for supercontinuum (SC) generation extending 0.4 μm to 2.0 μm, when excited by a 50 fs input pulse of 800 nm pumping wavelength, 79 MHz repetition rate and a coupled average power of 135 mW corresponding to pulse energy of 1.71 nJ in a 10 cm DC-PCF. The PCF and the SC spectra thus showed desirable properties for applications in biological sensors, optical fiber communication, frequency metrology and optical coherence tomography.

An efficient system for nonlinear parameter characterization in Highly Nonlinear Fiber (HNLF) is described using four wave mixing (FWM) technique, the FWM plays an important role in enhancing the spectrum development in most cases. The Nonlinear parameters like zero-dispersion wavelength (ZDW), chromatic dispersion (CD) and the non-linear coefficient of HNLF were successfully investigated using this technique. The results of this technique have been almost identical to factory specifications. By FWM technique, a CD at 1550 nm slope is obtained from 0.007 ps.nm-2km-1, ZDW of 1531 nm and nonlinear parameters of 10.7 W-1km-1.

As a basic study of a practical method for predicting the sound insulation performance of windows, this report presents a study of the sound reduction index of windows with single glazing, below a critical frequency. First, the results calculated by an existing theory for a single plate for the sound reduction indices are compared with measured results of actual windows to assess the theory’s applicability for evaluating the sound insulation performance of windows. Then, a regression analysis is employed to measure the results of a certain number of actual windows to explore a further development of a more practical prediction. The following findings were obtained: (1) Sound reduction indices of actual fixed windows are predictable using Sewell’s transmission theory for a single plate. However, sound reduction indices of openable windows, especially those of sliding windows, are strongly affected by gaps in the window frame. Therefore, predicting sound reduction indices of all windows accurately is difficult if using only one theory. (2) The frequency slope of the window reduction index is much lower than that of the mass law. Regression analyses indicate that the frequency slope of the reduction index of all examined windows is 3.0 dB per octave, on average.

Low-frequency noise is a growing problem in large structures of modern transportation technologies. In this study, we report a large-scale acoustic panel made of double-layer membrane-type metamaterials (DMAMs) for broadband noise reduction. A complete theoretical model based on the unit cell is fully developed and extended for finite multi-celled membrane-type acoustic metamaterial (MAMs) array. A large-scale acoustic panel constructed from 8 × 8 DMAM unit cells is proposed. To deal with the global compliance of the large-scale support structure, the double-layer panel frame structure with large bending stiffness is designed to shift the global resonances to higher frequencies and provide an efficient way to well maintain the MAM's performance. Moreover, the double-layer configuration further guarantees ultra high transmission loss within the frequency range of interest. Experiments are carried out to validate the analytical and numerical predictions. Excellent transmission loss ranging from 20 to 59 dB within ten third octave bands (0.32–2.5 kHz) is observed, deeply breaking the mass density law. We believe the proposed design and the associated theoretical model could serve as an efficient tool for designing acoustic metamaterial-based panels and soundproof walls with high noise reduction in low/middle frequency regions.

We propose an on-chip cascaded structure consisting of a microresonator and a slot waveguide to generate the high-performance supercontinuum harnessing the dual pump scenario. Utilizing a single CW pump with the power of only 0.1 W, the dissipative Kerr soliton with the full width at half maximum of 69.2 fs and the peak power of 103.3 W is generated and couples out the microresonator together with the CW pump to serve as a dual pump seed for the supercontinuum generation in the followed slot waveguide. The slot waveguide built upon a silicon-organic hybrid structure is carefully designed to possess remarkable nonlinearity and appropriate dispersion profile for smooth and broadband supercontinuum generation. We have numerically achieved the 1.56 octave-spanning supercontinuum spanning 1 ~ 3 μm with the proposed dual pump scenario. The supercontinuum generated by the dual pump scenario shows flattened, broadband, and quasi-right-angled-trapezoid shape, along with good coherence. Compared with the single pump scenario of CW or soliton pulse only, the supercontinuum generated by the dual pump scenario possesses the much stronger spectrum, broader spanning, and medium coherence. Our work opens up a new path for on-chip and cost-effective supercontinuum generation with the high performance of intensity, bandwidth, and coherence.

We developed a broadband terahertz wave circular polarizer that consists of a two-dimensional (2D) array of three-dimensional metallic helices. Each helix operates in an axial mode of operation where the wavelength of resonance is comparable to the dimensions of the helix. We evaluated the performance of the polarizer using standard terahertz time domain spectroscopy, and we confirmed that the array of helices transmits a circularly polarized terahertz wave with opposite handedness as that of the helices. The polarizer covers the frequency range from 117 GHz to 208 GHz, close to one octave. We obtained the ellipticity of the circularly polarized terahertz wave close to unity in this frequency band.

The generation of high-peak-power, few-cycle mid-infrared (MIR) pulses using coherent beam combination and nonlinear pulse compression techniques simultaneously is demonstrated. The two pulses, with identical pulse energy of 2.8 mJ and pulse duration of 160 fs, are coherently combined at the input end of a krypton-filled hollow-core fiber (HCF), and then the bandwidth of the combined pulse is broadened to near an optical octave due to strong phase modulations, and the temporal width is compressed into a few-cycle regime. Finally, a 2.7 mJ, 22.9 fs, 20 Hz laser at 4 μm can be obtained, and the pulse peak power is greatly enhanced compared with that of conventional single-channel optical parametric chirped pulse-amplification systems. Furthermore, the peak power generated from this system has the prospect of further scaling up through use of more channels of coherent combination, which can pave a way to generate higher peak power ultra-intense MIR pulses for strong-field physics.

We report on supercontinuum generation in silicon carbide (6H-SiC), pumped by tunable femtosecond pulses in the wavelength range of 1.3 - 2.4 μm, which cover the regions of normal, zero, and anomalous group velocity dispersion of the material. More than an octave spanning infrared supercontinuum spectra were measured, demonstrating almost constant blue cut-offs around 0.9 μm. Low energy thresholds for supercontinuum generation (depending on the pump wavelengths, but generally below 200 nJ) were demonstrated due to large nonlinear refractive index of the material (n2 = 97 ± 19 × 10−16 cm2/W), which was experimentally evaluated by measurement of the nonlinear transmission at 2.0 μm.

Octave-spanning optical frequency combs (OFCs) are essential for various applications, such as precision metrology and astrophysical spectrometer calibration. In this Letter, we demonstrate, for the first time to our knowledge, the generation of octave-spanning Kerr frequency combs ranging from 1150 to 2400 nm in aluminum nitride (AlN) microring resonators, by pumping the T M 00 modes at 250 mW on-chip power. By simply adjusting the pump detuning, we observe the transition and coexistence of Kerr OFC and stimulated Raman scattering. For the T E 00 mode in the same device, a broadband Raman-assisted frequency comb is demonstrated by adjusting the pump power and tuning. These results indicate a crucial development for the fundamentals of nonlinear dynamics and comb applications in AlN.

We phase locked an octave-spanning optical frequency comb based on a laser-diode-pumped Kerr-lens mode-locked Yb:KYW laser to a reference laser. We controlled the cavity length of the mode-locked laser to phase lock the mode frequency of the comb to the reference laser. This was conducted using a fast piezoelectric-actuated mirror on a lead-filled mount, which was aimed at damping the mechanical resonances. We achieved a servo bandwidth of 200 kHz, a residual phase noise of 0.47 rad, and a power concentration to a carrier of 91%. To extend the locking duration of the carrier-envelope offset frequency, we compensated its slow drift using the position of the Yb:KYW crystal while the pump-laser power was controlled to achieve its phase locking. We continuously maintained the full phase locking of the comb for 3 h until the reference lasers were out of lock.

We report, to the best of our knowledge, the first super-octave femtosecond polycrystalline Cr:ZnS laser at the central wavelength 2.4 µm. The laser is based on a non-polarizing astigmatic X-folded resonator with normal incidence mounting of the gain element. The chromatic dispersion of the resonator is controlled with a set of dispersive mirrors within one third of an optical octave over 2.05–2.6 µm range. The resonator’s optics is highly reflective in the range 1.8–2.9 µm. The components of the oscillator’s output spectrum at the wavelengths 1.6 µm and 3.2 µm are detected at –60 dB with respect to the main peak. Average power of few-cycle Kerr-lens mode-locked laser is 1.4 W at the pulse repetition frequency 79 MHz. That corresponds to 22% conversion of cw radiation of Er-doped fiber laser, which we used for optical pumping of the Cr:ZnS oscillator.

High-field terahertz (THz) wave is a powerful tool for investigating ultrafast dynamics such as the motion of electrons, the vibration of crystal lattices, the precession of spin, etc. In this letter, we demonstrate the generation of intense single-cycle THz pulses from an organic crystal DSTMS (4-N, N-dimethylamino-4'-N'-methyl–stilbazolium 2,4,6–trimethylbenzenesulfonate) via optical rectification. The generated THz field is characterized by single-shot electro-optic sampling with a linearly chirped probe beam. Meanwhile, the spectrum of the infrared pump is broadened to an octave which supports a 1.9-cycle pulse duration. The proposed scheme displays a sophisticated platform of efficient high-field THz generation, single-shot THz measurement, and a broadband mid-infrared source which is naturally synchronized with the THz pulses.

We experimentally demonstrate supercontinuum (SC) generation in a germanium-on-silicon waveguide. This waveguide exhibits propagation loss between 1.2 dB/cm and 1.35 dB/cm in the 3.6 µm–4.5 µm spectral region for both transverse electric (TE) and transverse magnetic (TM) polarizations. By pumping the waveguide with ∼200 fs pulses at 4.6 µm wavelength, we generate a mid-infrared (IR) SC spanning nearly an octave from 3.39 µm to 6.02 µm at the −40 dB level. Through numerical analysis of the evolution of the SC, we attribute the current limit to further extension into the mid-IR mainly to free-carrier absorption.

The article is about a comprehensive study of dissipative silencers of complex shapes. Analyzed the acoustic efficiency of such silencers. The sound absorption coefficient determined from experimental data. The acoustic properties of plate silencers take into account that coefficient. Presented the results of verification of models with plates of constant thickness. Considered the plates of complex shapes: uniform thickness change, convex and concave. Obtained results of modeling the acoustic efficiency of silencers with complex shape plates. These results are for different values of the mean integral thickness for the octave bands frequencies. Determined the dependence of the length of complex shapes silencers on their mean integral thickness. Presented the results of mathematical modeling of the airflow in silencers to determine their aerodynamic drag. The calculations showed that there is an optimal shape and mean integral thickness of the plates. Under which conditions the aerodynamic resistance of the silencer is minimal.

The fundamental problem in the battle against aircraft noise on areas surrounding airports is to determine the sound pressure level in the audible frequency range as well as the composition of the noise spectrum. Today, we have tools enabling the modeling of the influence of noise on the environment. However, these models allow only a quantitative assessment. The authors propose to develop a model that enables an analysis of the sound frequency structure in airport nearby areas. Several noise measurements during the F-16 Block 52+ aircraft takeoffs were conducted using a unique recording system. Based on the sound data processing and proposed analysis, the novel octave sound spectrum (between 16 and 16000 Hz) model in distance function (till 1600 m) was elaborated. Moreover, the model was statistically verified and validated by more noise measurements which has proven high results efficiency (the residuum values do not exceed 3 dB).

Transverse passages are ubiquitous in urban subways, and they pose serious mutual threats to the two adjacent tunnels they connect. In this paper, the frequency sweep loads were applied in model tests and the influence mechanism of integral transverse passage (ITP) was studied by using the one-third octave of the frequency response function (FRF). Subsequently, a new assembled transverse passage (ATP) was proposed and its vibration attenuation effect was studied. The results showed that, when the frequency sweep load is applied to one tunnel, the adjacent tunnel is more susceptible to a load that has a central frequency of 12.5–80 Hz due to the existence of ITP. The closer the loading frequency is to 31.5 Hz, the greater the impact on the adjacent tunnel becomes. When an ATP is used, the vertical acceleration level (VAL) of the tunnel to which the load is applied will increase by 1.3 dB, while that of the adjacent tunnel will decrease by 7.2 dB, and the transverse passage will decrease by 8.7 dB. Compared to the ITP, when the lining structure of an adjacent tunnel is closer to the ATP, the reduction in the vibration response of the structure is more pronounced, and the vibration response is reduced over a larger central frequency range.

New acoustic multilayer absorber fabricated by coupling closed-cell metallic foam and open-cell polymeric foam, which aimed to develop a practical use of metallic foam in the noise control application. In prior, the individual sound absorption coefficient of both foam materials with different thicknesses measured by the impedance tube method as per ASTM E-1050. Using inverse characterization technique, the intrinsic properties needed for five parameter models in a numerical study are predicted. The measured characteristic impedance, complex wave propagation, and sound absorption coefficient of the individual foams are in close agreement with the prediction. Subsequently, a different configuration of multilayer absorber is modeled using obtained properties, and their acoustic performance is evaluated. The result indicates that the coupling of polymeric foam with metallic one exhibits enhanced sound absorption and usage of closed-cell metallic foam in noise control material. Furthermore, the result demonstrates that absorption capability entirely relies on the placement of polymeric foam in the configuration. The proposed hybrid multilayer absorber coupled with test bench car for interior acoustic study, where 5–30 dB is reduction is noticed in 1/3rd octave plot.

Background: Utility of frequency tuning of ocular vestibular evoked myogenic potential (oVEMP) for evaluation of utricular function in individuals with Meniere’s disease is a recent development. However, there is dearth of studies regarding its utility in differential diagnosis of Meniere’s disease from other vestibular pathologies. Purpose: The present study aimed at investigating the feasibility of frequency tuning of oVEMP in discriminating Meniere’s disease from benign paroxysmal positional vertigo (BPPV). Research Design: Static group comparison. Study Sample: oVEMPs were acquired from 36 individuals, each with unilateral Meniere’s disease and unilateral BPPV. Thirty-six age- and gender-matched healthy individuals formed comparison group for each of the two clinical groups. Intervention: Contralateral oVEMPs were recorded from both ears of all the participants. Data Collection and Analyses: The responses pertaining to octave and mid-octave frequencies from 250 to 4000 Hz, one frequency presented at a time, were recorded from infra-orbital electrodes (noninverting placed 1 cm below the lower eyelid and inverting 2 cm below the inverting on the cheek) with forehead as ground. Starting intensity was 125 dB peSPL with subsequent reductions in 10-dB steps to arrive at threshold. The stimuli were delivered to the ear at a rate of 5.1 Hz. The frequency corresponding to the largest peak-to-peak amplitude, best threshold, and/or largest peak-to-peak amplitude at thresholds was considered as the tuning frequency. Proportions of ears with frequency tuning at a particular frequency were compared between the groups Results: The frequency tuning at 1000 Hz was found to exist in a significantly higher proportion of affected ears with Meniere’s disease than the comparison group as well as ears with BPPV (p < 0.05). Using a criterion point of frequency tuning at 875 Hz, the sensitivity and specificity for identifying Meniere’s disease was found to be 68% and 100%, respectively. Conclusion: The shift in frequency tuning is an efficient parameter for not only discriminating Meniere’s disease from healthy individuals but also distinguishing it from BPPV. Therefore, frequency tuning is recommended as a test parameter of oVEMP for identification of Meniere’s disease.

We report on the generation of multiple-octave supercontinuum laser source spanning from 0.5 μm to 11 μm induced by multi-filamentation in a ZnSe crystal. The generated supercontinuum is both spatially and spectrally characterized. It is then exploited in a proof-of-principle experiment for methane spectroscopy measurements by means of the supercontinuum absorption spectroscopy technique. The entire absorption spectrum is successfully recorded within the whole spectral bandwidth of the supercontinuum. Experimental results are in fairly good agreement with the HITRAN database, confirming the reliability and stability over several hours of the generated supercontinuum.

A field test of environment vibration due to subway was carried out so as to investigate the vibration-alleviating effect of rail suspension fasteners in both time and frequency domains. The experimental results show that the time-domain vertical ground vibration accelerations would transform from several concentrated vibrations to the decentralized and uniform ones after replacement of common rail fasteners with rail suspension fasteners. Moreover, rail suspension fasteners have more significant vibration-mitigation effect on the time-domain peak particle accelerations (PPAs) at the nearer positions than at the farther ones, and the minimum PPA induced by common rail fasteners is still higher than the maximal PPA caused by rail suspension fasteners at all measuring positions. In frequency domain, the vibration-reduction effect of rail suspension fasteners is more remarkable in the dominant 1/3 octave center frequencies of 50-125 Hz than in the non-dominant ones from 1 to 40 Hz. Compared with common rail fasteners, the highest vibration acceleration levels (VALmax) in the dominant 1/3 octave center frequencies between 50 and 125 Hz at all measuring positions decrease by 8.7-21 dB after adoption of rail suspension fasteners. Additionally, the integrated VLzs in 1/3 octave center frequencies of 1-125 Hz at all measuring positions are ranged from 77.1 dB to 66.5 dB, evidently higher than the China’ standard threshold of 65 dB, before replacement of common rail fasteners, while the integrated VLzs are framed between 68.3 and 57.3 dB, mostly less than the threshold, after application of rail suspension fasteners.

Hearing sensitivity in captive Atlantic bottlenose dolphins was assessed using a portable electrophysiologic data collection system, a transducer attached to the pan region of the mandible, and non-invasive recording electrodes. The auditory steady-state response (ASSR) was evoked using sinusoidal amplitude-modulated tones at half octave steps from 20–160 kHz and utilized to determine the upper frequency limit of hearing (i.e., the frequency at which threshold was ≤ 120 dB re 1 μPa). An auditory brainstem response (ABR) was then recorded to a moderate-amplitude click (peak-equivalent sound pressure level of 122 dB re 1 μPa) and examined to determine if relationships existed between the upper frequency limit of hearing and the waveform characteristics of the click-evoked ABR. The ASSR and click-evoked ABR were measured in 6 bottlenose dolphins with varying hearing sensitivity and frequency range of hearing. A significant relationship existed between click-evoked ABR wave amplitudes and the upper frequency limit of hearing. Test times for assessment using frequency-specific ASSR and click-evoked ABR were ∼45 minutes and 1 minute, respectively. With further definition of normative data, measurement of click-evoked ABRs could form the basis of an expedited electrophysiologic method for hearing screening in marine mammals.

Objectives/Hypothesis To investigate the impact of subway station design on platform noise levels. Study Design Observational. Methods Continuous A-weighted decibel (dBA) sound levels were recorded in 20 New York City subway stations, where trains entered on either a straight track or curved track in 10 stations each. Equivalent continuous noise levels (Leq) at various locations on the boarding platform (inbound end, midplatform, and outbound end) during train entry and exit were compared between the straight and curved stations in broadband as well as narrow one-third octave bands. Results Overall, curved stations trended louder than straight stations, although the difference in broadband Leq did not reach statistical significance (curve, 83.4 dBA; straight, 82.6 dBA; P = .054). Noise levels were significantly louder at the inbound end of the platform during train entry (inbound, 89.7 dBA; mid, 85.5 dBA; outbound, 78.7 dBA; P < .001) and at the outbound end during train exit (inbound, 79.7 dBA; mid, 85.3 dBA; outbound, 89.1 dBA; P < .001). Narrow band analysis showed that curved stations were significantly louder than straight stations at 100 Hz and high frequencies from 8 to 20 kHz. Peak impact levels ranged from 104 to 121 dBA. Conclusions Curved stations have a different noise profile compared to straight stations and are significantly louder than straight stations at high frequencies. Designing stations with straight tracks within the platform can help reduce commuter noise exposure. Level of Evidence NA Laryngoscope, 2016

OBJECTIVE This study aims to identify electrode contact location and to assess frequency deviation between predicted and actual frequency allocation maps in cochlear implant (CI) users. STUDY DESIGN AND METHODS This is a retrospective clinical study. Flat-panel computed tomography (FPCT) scans were collected for 17 CI users. Cochlear length was measured using three-dimensional curved multiplanar reconstruction on high-resolution secondary reconstructions. Each electrode's percentage of distance from the base of the helicotrema was measured, and a modified Greenwood's function was applied. The patients' frequency allocation maps were retrieved from electronic medical records and compared with their calculated characteristic frequencies. RESULTS Our results revealed that reprogramming based on FPCT imaging findings might improve 83% (n = 216) of 260 electrode contacts. The most basal and apical electrodes (12, 11, 10, 5, 4, 3, 2, and 1) most consistently deviated (>83% of the time) from their theoretical characteristic frequencies; the basal electrodes undershot and the apical electrodes overshot their theoretical values. Frequency mismatch between the characteristic frequencies of auditory neurons and programmed center frequencies ranges from 0.41 to 1.51 in octave bands. CONCLUSIONS Using FPCT imaging and a modified Greenwood's function, we identify a mathematical discrepancy between theoretical and actual CI placement with respect to frequency-place mapping. We demonstrate a clinically reproducible and direct assessment of frequency-place mismatch. Our individualized calculations account for inter-individual variability in cochlear lengths, operative differences in insertion depths, and electrode array kinking within the cochlea. The benefits of allocating electrode contact frequencies to their tonotopy-derived locations in the cochlea were not investigated in this study, and future prospective trials are needed to demonstrate the consequences of personalized pitch mapping for CI users with respect to speech and pitch perception.

The work objective is to describe the theoretical and experimental research of the vibration attenuation coefficient of the wage wheels on the electric locomotive underframe. Studying the vibro-acoustic characteristics at the workplaces of the locomotive crews shows that the excess of the octave sound-pressure levels over the maximum permissible values is largely determined by the noise structural component which is generated by vibrations of the body parts. The vibration velocity calculation is based on the energy methods traditionally used for the energy-closed circuits. The system of equations takes into account not only the geometric parameters of the elements, their physical and mechanical properties, but also the vibration power from the locomotive wheel pairs introduced into the base body under the speed conditions. For the engineering analysis of the vibration spectra of the body parts, and, respectively, of the sound-pressure levels when evaluating the introduced vibration power, it is expedient to use a frequency dependent value of the vibration reduction factor. This is especially important at the machine designing stage. Therefore, the results of the experimental study of the given value and the development of the regressional dependences for various motion speeds on this basis are presented.

Optical frequency combs enable precision measurements in fundamental physics and have been applied to a growing number of applications, such as molecular spectroscopy, LIDAR and atmospheric trace-gas sensing. In recent years, the generation of frequency combs has been demonstrated in integrated microresonators. Extending their spectral range to the visible is generally hindered by strong normal material dispersion and scattering losses. In this paper, we report the first realization of a green-light frequency comb in integrated high-Q silicon nitride (SiN) ring microresonators. Third-order optical non-linearities are utilized to convert a near-infrared Kerr frequency comb to a broadband green light comb. The 1-THz frequency spacing infrared comb covers up to 2/3 of an octave, from 144 to 226 THz (or 1327-2082 nm), and the simultaneously generated green-light comb is centered around 570-580 THz (or 517-526 nm), with comb lines emitted down to 517 THz (or 580 nm) and up to 597 THz (or 502 nm). The green comb power is estimated to be as high as -9.1 dBm in the bus waveguide, with an on-chip conversion efficiency of -34 dB. The proposed approach substantiates the feasibility of on-chip optical frequency comb generation expanding to the green spectral region or even shorter wavelengths.

The application of adaptive neural-fuzzy inference system (ANFIS) to predict the total weighted vibration acceleration of a trailer seat pulled by a two-wheel tractor is set out in the present paper. The vibration acceleration signals were obtained in a field experiment using a 9.5 kW two-wheel tractor. Three accelerometers were installed at three orthogonal directions according to ISO 2631-1 standard on the trailer seat for measuring and recording the vibration acceleration signals. The two-wheel tractor consumed diesel–biodiesel fuel blends, and the engine speed and gear ratio were varied to cover normal range of operation in transportation conditions on asphalt rural road. The digital recorded vibration acceleration signals in time domain were converted to the frequency domain using Fast Fourier Transform algorithm, and the one-third octave frequency bands were obtained. The one-third octave frequencies were weighted according to the ISO standard. Altogether, 100 patterns were generated for training and evaluation of ANFIS. The input parameters of ANFIS were the tractor engine speed, transmission gear ratio of the tractor and fuel blend type, and the output parameter was the trailer seat total weighted vibration acceleration. The ANFIS structure was designed based on the grid partition, fuzzy c-means clustering and subtractive clustering. The results revealed that the ANFIS with subtractive clustering method was the best for accurate prediction of the total weighted vibration acceleration of the trailer seat. The number of rules, root-mean-square error (RMSE) of train, RMSE of test, correlation coefficient (R) of train and R of test values for the optimized structure were 5, 0.1479, 0.2141, 0.9175 and 0.8804, respectively.

To create a project of broadband spectrum analyzer combined type in a range of sound frequencies applied the basic principles of graphical programming environment LABVIEW. Frequency channel analyzer are presented in the traditional form of acoustic measurements: a octave, half octave and one-third octave filters. Each frequency channel is assumed to calculate the spectrum by FFT (fast Fourier transform) within the band defined by this channel. The draft provides for a system calibration and adjustment of the analyzer, using the tonal and noise-like calibrating signals and provides the ability to display the results in a linear and logarithmic scale. The Bible. 4, Fig. 1.

In parallel to the ultrasonic noise assessment procedures and research activity in the field there have appeared several papers in the domain of so called high-frequency audiometry which covers the range of frequencies 8-20 kHz. They are important for recognizing the harmfulness and hazard of the audible high frequency sound components in the same range as the one of the low frequency ultrasonic noise. On the other hand there exists a certain inconsequent situation in the general approach to the problem of ultrasonic noise hazard assessment in work places environment which concerns the convention to include the frequency range of 10-20 kHz to the domain of ultrasonics. The range consists of one third octave bands of central frequencies: 10, 12.5, 16, 20 kHz and conventionally is called low frequency ultrasonic noise though at least the components of the two lowest bands are naturally audible by a majority of population (mainly young people).The paper presents a discussion related to some achievements of the two domains and some conclusions which could be useful for a more consequent description of the subject and could be taken into account in the future regulations for the ultrasonic noise assessment in work places environment.

The paper presents an investigation simulating transformations of an acoustic field at low frequencies indoors, when the sound source is outdoors. The investigation was performed using a simplified and 5-times-smaller physical model. The paper presents measured spatial sound pressure level (SPL) distribution at 1/3 octave bands as well as at discrete frequencies (at various room modes). Measurements inside the physical model (at a total of 2,565 points) confirm that when exposed to outdoor broadband noise, low-frequency sound pressure levels at 1/3 octave bands inside the room can differ by more than 30 dB, while at discrete frequencies measured SPL can vary by 50 dB or more. Below the calculated lowest room mode, due to resonant vibrations of physical model walls, large differences in sound pressure levels inside the model (up to 20.7 dB at 100 Hz 1/3 octave band and up to 32.4 dB at discrete Hz frequencies) were found. The investigation also includes analysis of levels in the corners of physical models compared to average sound pressure levels in the whole model space or some cross-sections, which shows that sound pressure levels in corners can be up to 10 dB lower. Calculation of the indoor average sound pressure level at low frequencies according to empirical formulas specified in standard ISO 12354-3 showed conformity between measurement and calculation results only in a part of the investigated range of frequency bands. Calculations using FEM at discrete frequencies gave more adequate results of sound pressure levels and their spatial distribution. FEM calculations proved that calculation of the average sound pressure level from measurements at points every 25 cm (every 5 cm in the physical model) can produce results close to the average of the sound pressure level of the room if it were measured at every possible position.

A 2.8-to-5.8 GHz harmonic VCO designed in a 28 nm UTBB FD-SOI CMOS process adopts a reconfigurable active core to save power at the lower oscillation frequencies, and to enable a trade-off between power consumption and phase noise at all frequencies. Interference caused by the magnetic coupling to and from the VCO inductor is greatly attenuated by resorting to an inductor in the shape of an 8. Simulations of the magnetic coupling between an 8-shaped inductor and a reference inductor show a reduction in magnetic coupling as high as 44 dB, depending also on size, orientation, and shape of the reference inductor. The UTBB FD-SOI CMOS process is instrumental to achieve a tuning range in excess of one octave at low power consumption. The VCO operates from 0.9 V and has a figure-of-merit of 186---189 dBc/Hz, depending on the oscillation frequency and the configuration of the oscillator core. The active area of the VCO is 380 ? 700 µm.

This paper explores the role of nonlinear dynamical phenomena in calculating the stress amplitude in large electronic components exposed to biaxial vibration loading. Nonlinear analytical studies are presented where a component exposed to combined axial and transverse vibratory base excitation is idealized using a nonlinear structural beam element with a tip mass. Harmonic and random base vibration excitation studies are conducted. The results provided in this paper confirm that Steinberg’s Octave rule may not be applicable for electronic components exposed to high amplitude multiaxial vibrations. In fact, components exposed to biaxial vibration are highly dependent on the phase angle between the orthogonal axes and the frequency ratio between the axial and transverse excitation frequencies. At critical frequency ratios, undesirable constructive and destructive stress amplification phenomena may appear if the system is exposed to a harsh multidirectional vibration environment.

This paper presents an approach for multizone wideband sound field generation using an efficient harmonic nested (EHN) dictionary for sparse loudspeakers’ placement and weight. Effectively, the nested arrays provide a priori knowledge of prospective loudspeaker locations based on the frequency bands of interest. The nested arrays are then further optimized in the Lasso stage to form an efficient loudspeakers’ location dictionary. The final loudspeaker locations and weightings are estimated by a two-stage Lasso-LS pressure matching optimization. In the first stage Lasso algorithm, the center band frequencies of octave bands from 1 kHz to 8 kHz were used to select active loudspeakers. A second stage then optimizes reproduction using all selected loudspeakers on the basis of a regularized LS algorithm. The results demonstrate that the proposed approach provides a solution for the multizone sound system with the mean squared error (MSE) under $-30\ \text{dB}$ across the targeted frequency range (500 Hz-16 kHz) using a linear array e.g. 13 loudspeakers. While, the single-stage LS approach generates the MSE peaks of $-10\ \text{dB}$ and $-9\ \text{dB}$ at 9 kHz within the active and silent zones respectively using an identical number of loudspeakers and array length.

Analysis of optical properties of mid-infrared-transparent nonlinear crystals reveals octave phase matching for a highly efficient optical parametric amplification of single-cycle electromagnetic field waveforms within the 3- to 12-μm wavelength range, recently demonstrated in experiments.

A method to enhance the filter slope of Brillouin-based photonic microwave filters is presented. This improvement is achieved by the combination of Brillouin gain and loss responses over phase-modulated signals. The experimental results show passband responses exhibiting a slope of 16.7 dB per octave, which corresponds with a threefold improvement in comparison to the natural Lorentzian response for the same gain., This work was supported in part by the Spanish Ministry of Economy and Competitiveness through TEC2016-80906-R project and by the European Union through TWEETHER project.

This talk describes the characteristic spectra resulting from turbulent water flow in multiple sections of the Provo and Colorado Rivers in Utah. For reference these rivers are characterized as medium-sized bedrock rivers, with Strahler orders of 5 and 7, respectively. Larson Davis 831C sound level meters were used to obtain two-second, one-third octave time histories. The spectra appear to be the superposition of two characteristic spectral curves possibly resulting from two different interactions within the turbulent section of the river. This two-source model for characterizing turbulent flow induced acoustics is similar to that observed in both the characteristic spectra for jet aircraft and for turbulent plasma flow. The higher frequency curve peaks between 700 and 1100 Hz and is almost certainly due to the Minnaert Frequency associated with resonating bubbles in the stream. This process and spectral curve appear similar to the fine spectral curve associated with Jet aircraft noise. The second curve is lower in frequency and peaks around 150 Hz and is most likely a result of interaction between the turbulent water and the ground.

The creation of a three-dimensional focal spot in air underpins applications in many fields. The literature presents many examples of focusing with acoustic metamaterials, but they are difficult to manufacture in large scale. Sonic crystals, are easier to make—since they are periodic arrangements of simple scatterers—but there are not many studies on achieving 3-D acoustic convergence through a 2-D sonic structure in air. In this study, we exploit the methods of sonic crystals to design the acoustic equivalent of a gradient index (GRIN) lens. We show that an extruded 2-D hexagonal lattice array of rigid cylinders with gradient diameters can be used to achieve the focusing of a 3-D shaped beam at audio frequencies i.e., a 2.5-D lens. We use finite-elements simulations with a commercial software to describe the device's performance in terms of band structure and equifrequency contours. We also present some preliminary measurements taken using a 3-D-printed model of our lens, designed for a focal length of 3.1 cm at 8 kHz. We find our 2.5-D GRIN lens works over a bandwidth of almost one octave. We discuss potential future uses, like in the correction of acoustical aberrations and in devices of flexible focal length.

A large concrete tower planned for construction was proposed at a site immediately adjacent to underground rail. The underground rail passenger trains pass frequently at a rate of once per 2-4 min 18–20 h per day. Excavation began and a caisson wall was constructed facing the underground vibration source. Preliminary measurements were made by placing an accelerometer on the East facing caisson wall. Attenuation was required in the 20-63 Hz frequency range. An isolation layer (GenieMat DM) was added to the caisson wall. The presentation will illustrate how this was done in combination with water proofing of the foundation and other onsite complexities. Large steel tie-backs are used to hold the caisson wall in place and these were treated to prevent any direct path for vibration. Upon completion of construction, measurements are taken and the level differences are presented. Attenuation exceeded the design and building code criteria at all one-third octave bands of concern.

Quantitative phase imaging (QPI) techniques are widely used for the label-free examining of transparent biological samples. QPI techniques can be broadly classified into interference-based and interferenceless methods. The interferometric methods which record the complex amplitude are usually bulky with many optical components and use coherent illumination. The interferenceless approaches which need only the intensity distribution and works using phase retrieval algorithms have gained attention as they require lesser resources, cost, space and can work with incoherent illumination. With rapid developments in computational optical techniques and deep learning, QPI has reached new levels of applications. In this tutorial, we discuss one of the basic optical configurations of a lensless QPI technique based on the phase-retrieval algorithm. Simulative studies on QPI of thin, thick, and greyscale phase objects with assistive pseudo-codes and computational codes in Octave is provided. Binary phase samples with positive and negative resist profiles were fabricated using lithography, and a single plane and two plane phase objects were constructed. Light diffracted from a point object is modulated by phase samples and the corresponding intensity patterns are recorded. The phase retrieval approach is applied for 2D and 3D phase reconstructions. Commented codes in Octave for image acquisition and automation using a web camera in an open source operating system are provided.

This publisher’s note contains corrections to Opt. Lett. 44, 4737 (2019) OPLEDP0146-959210.1364/OL.44.004737.

In this paper, a simplified car air cavity model for predicting the influence of an interior trim material on the cabin interior sound pressure level (SPL) was presented. This work studies a rigid-walled car cabin model with one flexible wall. The interior trim material (a porous sound-absorbing material) was mounted in between the enclosed car air cavity and the flexible wall. A single point acoustic source is used to acoustically excite the rigid-walled car air cavity model, where the loudspeaker is positioned at front corner of the car cabin to simulate noise entering via an airborne path. The variation of the car air cavity interior sound pressure level corresponding to the presence of different porous sound-absorbing materials was experimentally investigated for high frequencies. The acoustical effects of the interior trim porous material on the proposed structural and acoustic coupled system were predicted by using the Statistical Energy Analysis (SEA) method for noise in one third octave bands. The comparison of results revealed that the experimentally acquired car cabin interior sound pressure level agrees fairly well with the simplified SEA model, both with and without the porous sound-absorbing materials, for high frequency one third octave band levels.

Single-crystal aluminum nitride (AlN) possessing both strong Pockels and Kerr nonlinear optical effects as well as a very large band gap is a fascinating optical platform for integrated nonlinear optics. In this work, fully etched AlN-on-sapphire microresonators with a high-Q of 2.1 × 106 for the TE00 mode are firstly demonstrated with the standard photolithography technique. A near octave-spanning Kerr frequency comb ranging from 1100 to 2150 nm is generated at an on-chip power of 406 mW for the TM00 mode. Due to the high confinement, the TE10 mode also excites a Kerr comb from 1270 to 1850nm at 316 mW. In addition, frequency conversion to visible light is observed during the frequency comb generation. Our work will lead to a large-scale, low-cost, integrated nonlinear platform based on AlN.

Compact and powerful ultrafast light sources at high pulse repetition rates, based on mode-locked near infrared fiber lasers, are now widely available and are being used in applications such as frequency metrology, molecular spectroscopy, and laser micro-machining. The realization of such lasers in the mid-infrared has, however, remained a challenge for many years. Here we report a record-breaking three-stage fiber laser system that uses an Er-doped fluoride fiber as gain medium, delivering W-level few-cycle pulses at 2.8 µm at a repetition rate of 42.1 MHz. A fiber-based seed oscillator, cavity dispersion-managed by a pulse-stretcher, generates near-100-fs mid-infrared pulses with > 110 n m spectral bandwidth. These pulses are amplified to an average power of ∼ 1 W in a chirp-engineered fiber amplifier, and then compressed to ∼ 16 f s in a short length of highly nonlinear ZBLAN fiber, resulting in a more-than-octave-wide spectrum reaching from 1.8 µm to 3.8 µm with a total power of 430 mW.

This erratum presents the corrections to the Letter published in Opt. Lett. 44, 3146 (2019)OPLEDP0146-959210.1364/OL.44.003146.