Smooth Spectrum Research Articles

Multiple emission components in the Cygnus cocoon detected fromFermi-LAT observations

Context. Star-forming regions may play an important role in the life cycle of Galactic cosmic rays (CRs), notably as home to specific acceleration mechanisms and transport conditions. Gamma-ray observations of Cygnus X have revealed the presence of an excess of hard-spectrum gamma-ray emission, possibly related to a cocoon of freshly accelerated particles.Aims. We seek an improved description of the gamma-ray emission from the cocoon using ~13 yr of observations with theFermi-Large Area Telescope (LAT) and use it to further constrain the processes and objects responsible for the young CR population.Methods. We developed an emission model for a large region of interest, including a description of interstellar emission from the background population of CRs and recent models for other gamma-ray sources in the field. Thus, we performed an improved spectro-morphological characterisation of the residual emission including the cocoon.Results. The best-fit model for the cocoon includes two main emission components: an extended component FCES G78.74+1.56, described by a 2D Gaussian of extensionr68= 4.4° ± 0.1°−0.1°+0.1°and a smooth broken power law spectrum with spectral indices 1.67 ± 0.05−0.01+0.02and 2.12 ± 0.02−0.01+0.00below and above 3.0 ± 0.6−0.2+0.0GeV, respectively; and a central component FCES G80.00+0.50, traced by the distribution of ionised gas within the borders of the photo-dissociation regions and with a power law spectrum of index 2.19 ± 0.03−0.01+0.00that is significantly different from the spectrum of FCES G78.74+1.56. An additional extended emission component FCES G78.83+3.57, located on the edge of the central cavities in Cygnus X and with a spectrum compatible with that of FCES G80.00+0.50, is likely related to the cocoon. For the two brightest components FCES G80.00+0.50 and FCES G78.74+1.56, spectra and radial-azimuthal profiles of the emission can be accounted for in a diffusion-loss framework involving one single population of non-thermal particles with a flat injection spectrum. Particles span the full extent of FCES G78.74+1.56 as a result of diffusion from a central source, and give rise to source FCES G80.00+0.50 by interacting with ionised gas in the innermost region.Conclusions. For this simple diffusion-loss model, viable setups can be very different in terms of energetics, transport conditions, and timescales involved, and both hadronic and leptonic scenarios are possible. The solutions range from long-lasting particle acceleration, possibly in prominent star clusters such as Cyg OB2 and NGC 6910, to a more recent and short-lived release of particles within the last 10–100 kyr, likely from a supernova remnant. The observables extracted from our analysis can be used to perform detailed comparisons with advanced models of particle acceleration and transport in star-forming regions.

Design and verification of an all-dielectric metamaterial and its application in wide-spectrum measurement of clothing fabrics

The application of metamaterial sensors is a hot topic in the field of material measurement. However, the resonant absorption modes are difficult to be eliminated due to many metamaterial sensors containing metal arrays. In measurements of the clothing fabrics, absorption rate requires a smooth spectrum in a wide frequency range. Here, an all-dielectric metamaterial is proposed and measured, and a smooth absorption spectrum is achieved (average absorptivity of 25.2%). When this metamaterial is covered by a fabric sample (Polyester), the measured average absorptivity is 41.5%. When the thickness of the fabric sample Polyester is set to be 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm, the measured average absorptivity of the Polyester is: 41.5%, 48.3, 57.6, 62.1, respectively. Moreover, four fabric samples are measured and the achieved absorptivity is: 41.5%, 25.1%, 34.3%, and 56.6%, respectively. The simulated results are close to the measurement results. This all-dielectric metamaterial demonstrates the feasibility of clothing fabric measurement.

Efficient continuous wave and broad tunable lasers with the Tm:GdScO3 crystal.

The spectroscopic properties and tunable laser performances of the orthorhombic perovskite Tm:GdScO3 crystal grown by the Czochralski method are comparatively studied for polarization along different crystallographic axes. The polarized emission spectrum of Tm:GdScO3 along the b-axis exhibits, to the best of our knowledge, the broadest bandwidth among all the single Tm3+-doped bulk gain media, indicating the strong inhomogeneous line broadening of Tm3+ ions in GdScO3 and thus leads to a broad and smooth gain spectrum. Tunable laser operation with a tuning range as broad as 321 nm from 1824 nm to 2145 nm is achieved, which indicates its potential for few-optical-cycle pulse generation in the 2-µm spectral range.

Broadband soft X-ray source from a clustered gas target dedicated to high-resolution XCT and X-ray absorption spectroscopy.

The development of the broad-bandwidth photon sources emitting in the soft X-ray range has attracted great attention for a long time due to the possible applications in high-resolution spectroscopy, nano-metrology, and material sciences. A high photon flux accompanied by a broad, smooth spectrum is favored for the applications such as near-edge X-ray absorption fine structure (NEXAFS), extended X-ray absorption fine structure (EXAFS), or XUV/X-ray coherence tomography (XCT). So far, either large-scale facilities or technologically challenging systems providing only limited photon flux in a single shot dominate the suitable sources. Here, we present a soft, broad-band (1.5 nm - 10.7 nm) soft X-ray source. The source is based on the interaction of very intense laser pulses with a target formed by a cluster mixture. A photon yield of 2.4 × 1014 photons/pulse into 4π (full space) was achieved with a medium containing Xe clusters of moderate-size mixed with a substantial amount of extremely large ones. It is shown that such a cluster mixture enhances the photon yield in the soft X-ray range by roughly one order of magnitude. The size of the resulting source is not beneficial (≤500 µm but this deficit is compensated by a specific spectral structure of its emission fulfilling the specific needs of the spectroscopic (broad spectrum and high signal dynamics) and metrological applications (broad and smoothed spectrum enabling a sub-nanometer resolution limit for XCT).

Separation theorems in the commutative algebra of -rings and applications

In this paper we state and prove ad hoc “Separation Theorems” of the so-called Smooth Commutative Algebra, the Commutative Algebra of -rings. These results are formally similar to the ones we find in (ordinary) Commutative Algebra. However, their proofs are not so straightforward, since they depend on the introduction of the key concept of “smooth saturation.” As an application of these theorems we present an interesting result that sheds light on the natural connection between the smooth Zariski spectrum and smooth real spectrum of a -ring, the -analog of the real spectrum of a commutative unital ring.

Custom terahertz waveforms using complementary organic nonlinear optical crystals.

Organic nonlinear optical (NLO) crystals are among the most efficient (>1%) terahertz (THz) radiation generators. However, one of the limitations of using organic NLO crystals is that the unique THz absorptions in each crystal make it difficult to obtain a strong, smooth, and broad emission spectrum. In this work, we combine THz pulses from two complementary crystals, DAST and PNPA, to effectively fill in spectral gaps, creating a smooth spectrum with frequencies out to 5 THz. The combination of pulses also increases the peak-to-peak field strength from 1 MV/cm to 1.9 MV/cm.

Flattening laser frequency comb spectra with a high dynamic range, broadband spectral shaper on-a-chip.

Spectral shaping is critical to many fields of science. In astronomy for example, the detection of exoplanets via the Doppler effect hinges on the ability to calibrate a high resolution spectrograph. Laser frequency combs can be used for this, but the wildly varying intensity across the spectrum can make it impossible to optimally utilize the entire comb, leading to a reduced overall precision of calibration. To circumvent this, astronomical applications of laser frequency combs rely on a bulk optic setup which can flatten the output spectrum before sending it to the spectrograph. Such flatteners require complex and expensive optical elements like spatial light modulators and have non-negligible bench top footprints. Here we present an alternative in the form of an all-photonic spectral shaper that can be used to flatten the spectrum of a laser frequency comb. The device consists of a circuit etched into a silicon nitride wafer that supports an arrayed-waveguide grating to disperse the light over hundreds of nanometers in wavelength, followed by Mach-Zehnder interferometers to control the amplitude of each channel, thermo-optic phase modulators to phase the channels and a second arrayed-waveguide grating to recombine the spectrum. The demonstrator device operates from 1400 to 1800 nm (covering the astronomical H band), with twenty 20 nm wide channels. The device allows for nearly 40 dBs of dynamic modulation of the spectrum via the Mach-Zehnders , which is greater than that offered by most spatial light modulators. With a smooth spectrum light source (superluminescent diode), we reduced the static spectral variation to ∼3 dB, limited by the properties of the components used in the circuit. On a laser frequency comb which had strong spectral modulations, and some at high spatial frequencies, we nevertheless managed to reduce the modulation to ∼5 dBs, sufficient for astronomical applications. The size of the device is of the order of a US quarter, significantly cheaper than their bulk optic counter parts and will be beneficial to any area of science that requires spectral shaping over a broad range, with high dynamic range, including exoplanet detection.

Chaotic RF Generator for Sub-1-GHz Chaos-Based Communication Systems: Mathematical Modeling and Experimental Validation

In this paper, we have studied, designed and realized a single-transistor chaotic generator with a smooth power spectrum of about −35 dBm in frequency bandwidth up to 1 GHz. The chaos generator model is described by a continuous-time six-dimensional autonomous system assuming an exponential nonlinearity. Chaotic behavior is characterized by bifurcation diagrams, Lyapunov exponents, phase portraits of the attractors and spectra of the oscillations, using both numerical and circuit simulations. Advanced Design System (ADS)-based simulations were carried out to support the theoretical analysis, and to validate the mathematical model. The simulations are carried out using real transistor parameters and taking into account the properties of the substrate, the influence of the board topology and the characteristics of the layout material. This simulation method known as EM/Circuit Co-Simulation allows the simulation results to approach as closely as possible to those of the experiments. In the light of the positive simulation results, the proposed structure is realized to demonstrate its feasibility, and to confirm the numerical results. The prototype is manufactured and mounted on a breadboard using the surface-mount devices and BFP193 bipolar junction transistor. After realizing the generator, we pushed it further towards perfection, through the proposal and realization of a broadband amplifier, in order to gain more bandwidth to improve the spectral characteristic of the generator, which makes it promising for many communication applications such as spread spectrum communication, direct chaotic communication, etc.

The spectrum of covariance matrices of randomly connected recurrent neuronal networks with linear dynamics

A key question in theoretical neuroscience is the relation between the connectivity structure and the collective dynamics of a network of neurons. Here we study the connectivity-dynamics relation as reflected in the distribution of eigenvalues of the covariance matrix of the dynamic fluctuations of the neuronal activities, which is closely related to the network dynamics' Principal Component Analysis (PCA) and the associated effective dimensionality. We consider the spontaneous fluctuations around a steady state in a randomly connected recurrent network of stochastic neurons. An exact analytical expression for the covariance eigenvalue distribution in the large-network limit can be obtained using results from random matrices. The distribution has a finitely supported smooth bulk spectrum and exhibits an approximate power-law tail for coupling matrices near the critical edge. We generalize the results to include second-order connectivity motifs and discuss extensions to excitatory-inhibitory networks. The theoretical results are compared with those from finite-size networks and the effects of temporal and spatial sampling are studied. Preliminary application to whole-brain imaging data is presented. Using simple connectivity models, our work provides theoretical predictions for the covariance spectrum, a fundamental property of recurrent neuronal dynamics, that can be compared with experimental data.

Investigation of the Possibility of Using Microspectrometers Based on CMOS Photodiode Arrays in Small-Sized Devices for Optical Diagnostics.

The article considers the potential applicability of C12880MA and C11708MA Hamamatsu microspectrometers, which are characterized by an extremely compact design, occupying a small volume of several cubic centimeters, in portable spectrometric equipment with spatial resolution for monitoring the optical properties of condensed scattering media. The development of methods for determining the reduced scattering and absorption spectral coefficients of radiation from various scattering materials and products allows us to speak about the possibility of real-time control of the volume concentration of optically active components included in them, for example, fat and water in dairy products. For this, it is necessary to provide sufficiently accurate spectra of diffusely reflected broadband light radiation at different distances between the points of radiation entrance and registration. The aim of the manuscript is to assess the possibility of using the considered microspectrometers in compact devices for optical diagnostics and control of the optical properties of condensed scattering media. The features of the connection diagram of these microspectrometers and the necessary methods for correcting the initially obtained spectral dependencies of diffusive reflection, which will be of interest to developers of spectral diagnostic equipment, are considered in detail. The need to eliminate the influence of the inhomogeneity of dark counts of a CMOS photodiode array is shown. The hardware functions of the C12880MA and C11708MA Hamammatsu microspectrometers, as well as the AvaSpec 2048L fiber-optic spectrometer, were experimentally measured and compared. Methods for correcting the nonlinearity of their reading scales and light characteristics, as well as improving their equivalent spectral resolution using digital Wiener filtering, are described. It is shown that the equivalent spectral resolution of C12880MA and C11708MA microspectrometers can be improved by about 40% when recording smooth spectra, subject to the condition that the resulting side oscillations are small. It is pointed out that in order to reduce the level of side oscillations in the corrected spectra with improved resolution, it is necessary to ensure the smoothness of the original spectra and a good signal-to-noise ratio. A conclusion is made about the possibility of using the considered microspectrometers in portable spectrometric equipment with careful consideration of their characteristics, the features of their switching circuit, and the necessary software.

Imprint of the temporal envelope of ultra-short laser pulses on the longitudinal momentum spectrum of e+e− pairs

The effect of the temporal pulse shape of intense pulses on the momentum distribution of ${e}^{+}{e}^{\ensuremath{-}}$ pairs is studied using the quantum kinetic equation. Two closely resembling temporal envelopes, namely, Gaussian and Sauter, keeping all the other pulse parameters the same, are considered to this end. Contrary to the common perception which can be gauged from the interchangeable use of these temporal profiles, the longitudinal momentum spectrum of the pairs created by the two pulses is found to differ significantly in all the temporal regimes. For the pulses having a few cycles of oscillations, the temporal profile of the pulse is revealed in the oscillatory interference pattern riding over the otherwise smooth longitudinal momentum spectrum at asymptotic times. The onset of the oscillation due to the quantum interference of reflection amplitudes from the scattering potential due to the pulses having a temporal structure of multiple barriers takes place for fewer-cycle oscillations for the Gaussian pulse compared to that for the Sauter pulse. Furthermore, the oscillation amplitude for the same number of oscillations within the pulse duration is larger for the Gaussian pulse. The presence of the carrier-envelope phase and the frequency chirping is found to magnify these differences. In the absence of any appreciable interference effect for the pulses having less than five oscillations, the longitudinal momentum spectrum has a higher peak value for the Sauter pulse at asymptotic times. On the other hand, before the transient stage of evolution, the peak of the spectrum shows the opposite trend.

INFLUENCE OF INPUT MOTION SCALING METHODS ON DECOUPLED SSI DYNAMIC ANALYSIS

Propagation of seismic waves through soil deposits may considerably alter theircharacteristics at surface. This ultimately influences the seismic performance of structures.The influences of soil deposits are included in seismic codes (e.g. Eurocode 8, EC8) by meansof proposed design response spectra for different soil classes used in design or retrofittingof structures. Nevertheless, a smooth design response spectrum cannot always representspectral response of an actual input motion over an engineering period of interest due toits irregular spectral shape. Subsequently, the seismic performance of a structure may beinsufficient when a design response spectrum is used. The interaction between soil andstructure may also affect the structural behaviour. This study aims to demonstrate theimpact of adoption of input motions and soil deposits with soil classes B, C and D on theseismic behaviour of one-bay, 1-storey structure modelled in OpenSEES For this purpose,two different approaches are chosen; (i) seven input motions recorded on ground surfaceare modified and applied to the model, (ii) seven outcrop motions are scaled according toEC8 and processed through the ideal soil deposits by conducting nonlinear site responseanalysis, then applied to the model. The results indicate that the model is exposed to moredrift responses when it is on softer soil deposit. In addition, imposing input motionsobtained at surface from nonlinear site response analysis cause higher drift responses thandirectly applying input motions.

A novel 0.2–7 GHz microwave hyperchaotic generator based on Hartley oscillator

In this paper, a miniaturized microwave-band hyperchaotic generator prototype has been designed and realized. By improving the topology of Hartley oscillator, the proposed single-stage common-collector structure oscillator enables us to generate a microwave 0.2–7 GHz smooth spectrum signal with a power around −30 dBm. Using BFP650 SiGe transistor as a non-linear component, the proposed circuit has been implemented and simulated then experimentally approved. Introducing the parasitic capacitors C BC and C BE and using the exponential model to describe the active component non-linearity, a simplified electrical model for the developed circuit has been proposed. To exhibit the deterministic chaotic character of the mentioned circuit, mathematical and schematic implementation results using Matlab and Advanced Design System (ADS) simulations have been presented. The concordance between the two simulation results permits us to adopt the simplified state equation model to describe the circuit behavior. The Lyapunov spectrum exponents representation allowed us to verify the hyperchaotic behavior in the presented generator. Finally, an autonomous simple prototype architecture of the generator using the PTFE (Polytetrafluoroethylene) substrate with ε r = 2.2 has been realized and experimentally validated. The achieved performances made the proposed circuit suitable for various fields of telecommunications.

Polarized spectroscopy and diode-pumped laser operation of disordered Yb:Ca3Gd2(BO3)4 crystal

We report on the growth, structure, polarized spectroscopy and efficient continuous-wave laser operation of an Yb3+-doped disordered calcium gadolinium borate crystal, Yb3+:Ca3Gd2(BO3)4 (Yb:GdCB). Yb:GdCB belongs to the orthorhombic class [sp. gr. Pnma, lattice parameters a = 7.1937(0) Å, b = 15.5311(3) Å, c = 8.6140(7) Å]. The structure disorder of this material originates from a random distribution of Ca2+ and Gd3+|Yb3+ cations over three non-equivalent lattice sites. This leads to broad and smooth (“glassy-like”) absorption and emission spectra at room and low temperatures. The stimulated-emission cross-section of Yb3+, σSE is 0.42×10−20 cm2 at 1025.1 nm for light polarization E || c and the luminescence lifetime of the 2F5/2 state is 644 µs. Continuous-wave laser performance of the Yb:GdCB crystal was evaluated under high-power diode-pumping at 976 nm for three crystal orientations along the crystallographic axes. For an a -cut crystal, a maximum output power of 5.58 W was achieved at ∼1057 nm with a slope efficiency of 51.7% and a linear laser polarization ( E || c ). The demonstrated power scaling capabilities and broadband emission properties of Yb:GdCB indicate that it is promising for generation of sub-50 fs pulses from passively mode-locked lasers at ∼1 µm.

Wiggler radiation at a low-emittance storage ring and its usage for X-ray absorption spectroscopy.

A wiggler is a high-power insertion device that was used in the past to produce a smooth wide-band X-ray spectrum. It is widely believed that on low-emittance synchrotrons this X-ray source loses its spatial and spectral homogeneity and therefore becomes less ideal than a scanning undulator. In this paper, we report on experimental and computational studies of an in-vacuum wiggler installed on the first fourth-generation synchrotron MAX IV. We investigate how several physical parameters affect the wiggler spectrum and propose a combination of a few of them that results in significant spectral smoothing. We also examine EXAFS spectra for possible distortions originating from the source imperfection. For this purpose, we scrutinize samples of various homogeneity. We conclude that wigglers are still an appropriate class of insertion devices, also on low-emittance synchrotrons.

Mode-locked fiber laser with coexistence of m ultiple solitons and noise-like pulses

Dissipative solitons (DSs) usually play an important role in understanding the intricate phenomena in various nonlinear systems. As a special regime in the dissipative system, noise-like pulses (NLPs) can have typical characteristics of ultra-broad and smooth spectrum, high pulse energy and low temporal coherence, making them a good candidate for many applications, including supercontinuum generation, industrial micromachining and optical metrology. In this paper, a noteworthy observation concerning the dynamics on coexistence of the multiple solitons and NLPs operation in a net-normal-dispersion passively mode-locked fiber laser based on nonlinear amplifying loop mirror (NALM) is reported. In the experiment, the stable DSs can be easily obtained at a proper pump power. When appropriately increasing the pump power and changing the polarization state, the DS operation can change to the NLP regime. When the fiber laser operates in an NLP state, the single soliton bunch contains multiple pulses with different temporal spacings. And the temporal interval between the adjacent pulses is in a range of several hundred picoseconds, which decreases from left to right with time changing, indicating that there are long-distance interactions among these multiple pulses and they gradually become stronger and stronger. Besides, the pulse number of single soliton bunches on the NLP operation increases almost linearly with pump power increasing. At a maximum pump power, there are eight pulses inside the single soliton bunch. With the increase of pump power, the average output power and pulse energy of these multiple solitons in the NLP state increase. The maximum average output power and pulse energy are 12.3 mW and 1.65 nJ, respectively. In addition, the real-time dynamic evolution of these multiple solitons in the NLP state is investigated by using the time-stretch dispersive Fourier-transform method. The results show that all the pulses in NLP regime actually consist of chaotic noise waves with stochastic intensities. We believe that this paper will be of significance in studying ultrafast fiber lasers and nonlinear optics. Moreover, we hope that these findings will be helpful in understanding the physical mechanism of NLPs and paving the way for exploring other complex soliton dynamics.

Use of the Normalized Design Parameters for Designing a Strip Speaker Operated by the Traveling-Wave Control Method

A strip speaker is the simplified panel speaker adopting a thin beam as the radiator, which is operated under the traveling-wave control method (TCM) with three actuators. The structural resonances are suppressed fundamentally by nullifying the reflected bending waves near the boundary, thus radiating a smooth sound spectrum in a wide frequency band. This study develops the design guidelines for such TCM-controlled strip speakers by investigating the effect of design variables on acoustic performances, such as the effective frequency range and the radiation efficiency. To this end, the acoustic performances are normalized by the size and physical properties of the beam so that a parametric study in the normalized domain can generalize the conditions for the desired acoustic performances. The result shows that the effective frequency range becomes wider when the beam material has a fast wave speed, and the radiation efficiency is enhanced as the beam density decreases. It is found that the two acoustic performances require a trade-off in selecting the actuator location and beam thickness. The suggested design procedure is validated using acrylic and aluminum beams having the same size. The aluminum beam has a faster wave speed, thus covering the effective bandwidth of 5800 Hz, 2.5 times wider than the acrylic case. On the other hand, the acrylic beam has five times higher radiation efficiency due to its low density. As a result, one can select the dimension and material of the beam appropriately to achieve the desired acoustic performance by using the suggested design method.

A low-cost spectrometer to analyse the purity of honey

Light spectrum dispersion is an exciting subjectin science because of its beautiful atmospheric colour phenomenon which attracts students. However, to see the phenomenon is not easy since it needs a spectrometer, which is commonly expensive. Therefore, the present study aims to describe a low-cost spectrometer for investigating lighting spectrum and analysing the purity of honey as a pedagogical students’ project. The spectrometer was constructed from a webcam connected to a laptop, a free spectrometer software, DVD disk, and black cardboard. The calibration of the developed spectrometer used an Argon (Ar) lamp. Afterwards, measurement tests were carried out by using Neon (Ne) and Xenon (Xe) lamps. A white light-emitting diode was used as a light source to measure several types of honey wavelengths. The results from the experiment show that the wavelength of Ar, Ne, and Xe are (503 ± 4) nm, (463 ± 3) nm, and (451 ± 3) nm respectively. The measurement accuracy of the spectrometer is 99.5%. In addition, the commercial honey characterisations show that pure honey tends to have an excellent and smooth spectrum with one peak. On the contrary, the adulteries honeys show a rough wave with many peaks representing the inhomogeneous ingredients. It is found that the average accuracy for honey spectrum is 99.8%. Moreover, the low-cost spectrometer can be built and used easily by students for educational purposes.

Fabrication and Characterization of a Thermophone Based on Laser-Scribed Graphene Intercalated with Multiwalled Carbon Nanotubes.

The low sound pressure level and high operating voltages of thermophones have limited their applications in the past. However, in recent years, utilizing nanomaterials in thermophones has improved their efficiency and applicability. Nanomaterials, especially carbon nanotubes and graphene, have the advantage of low heat capacity per unit area (HCPUA) and high electrical and thermal conductivity. Therefore, they require a low electrical input power and generate a high sound pressure level (SPL) by efficiently transferring heat to the surrounding fluid. Laser-scribed graphene (LSG) can generate smooth spectra acoustic emissions over a wide range of frequencies by means of thermoacoustic (TA) emission. In this work, a thermophone based on LSG intercalated with multiwalled carbon nanotubes (MWCNTs) is proposed. The effects of varying input power, duty cycle percentage and measuring distance on the sound pressure level (SPL) of thermophones are studied to extract maximum efficiency. The achieved SPL of LSG, normalized to the input power, has increased by approximately 11 dB by intercalating it with MWCNTs, which shows that our proposed material can be a potential candidate for an efficient thermophone.

Surface manifestation of stochastically excited internal gravity waves

ABSTRACT Recent photometric observations of massive stars show ubiquitous low-frequency ‘red noise’ variability, which has been interpreted as internal gravity waves (IGWs). Simulations of IGWs generated by convection show smooth surface wave spectra, qualitatively matching the observed red noise. Theoretical calculations using linear wave theory by Shiode et al. and Lecoanet et al. predict IGWs should manifest at the surface as regularly spaced peaks associated with standing g modes. In light of the apparent discrepancy between these theories and simulations/observations, we test the theories with simplified 2D numerical simulations of wave generation by convection. The simulations agree with the transfer function calculations presented in Lecoanet et al., demonstrating that the transfer function correctly models linear wave propagation. However, there are differences between our simulations and the g-mode amplitude predictions of Shiode et al. This is because that work did not take into account the finite width of the g-mode peaks; after correcting for this finite width, we again find good agreement between theory and simulations. This paper verifies the theoretical approach of Lecoanet et al. and strengthens their conclusion that IGWs generated by core convection do not have a surface manifestation consistent with observed low-frequency variability of massive stars.