Spectral Composition Research Articles

USING NEURAL NETWORKS FOR LANDMINE DETECTION

The issue of large mined areas and their expansion is critical due to their impact on safety and the economy. This article focuses on enhancing the efficiency of optical methods for detecting surface-laid landmines in humanitarian demining tasks. It demonstrates that one of the most promising optical methods for mine detection is hyperspectral imaging, which provides exceptionally precise analysis of the spectral composition of the radiation in the background-target environment. However, practical application of hyperspectral methods is significantly complicated by the vast size of mined territories. Therefore, mine detection must be automated. To address this challenge, the potential of artificial neural networks was investigated. The study proposes the integration of artificial intelligence, specifically RBF (Radial Basis Function) networks, to improve the efficiency and accuracy of object detection. The work compares traditional classification methods with innovative machine learning approaches. Algorithms were tested on both simulated and real data, enabling an evaluation of their ability to identify objects under varying spectral content conditions. The specific characteristics of the study area define the requirements for assessing the performance of technical tools: foremost, the probability of missing a signal must be minimized. At the same time, given the large-scale computations involved, the probability of false alarms should remain low. The study shows that RBF neural networks can detect mines with a low rate of false alarms. During network training with a large spread parameter, the sensitivity of the output to the spectral variability of pixels decreases. This allows the network to detect a target even at low fill coefficients. Thus, the research results indicate that the proposed methods significantly reduce false alarms and ensure high performance under real-world conditions.

MODEL OF THREE-PHASE ASYNCHRONOUS MOTOR WITH SHORT CIRCUIT ROTOR IN MATLAB PACKAGE

The presented paper examines the specifics of researching the mathematical apparatus of the model of a three-phase АМ with a short-circuited rotor in the matlab package. It has been proven that three-phase АМ with a short-circuited rotor form the basis of a modern electric drive in many branches of industry, agro-industrial complex and transport. A model was developed in the matlab package, which describes the operation of a frequency-regulated electric drive, taking into account theoretical analysis and experimental studies. In the scientific work, the task of combining mathematical modeling and modern computer technologies, which are based on application packages, is fulfilled, which gives the researcher the opportunity to deeply study the processes that occur in all links of the electric drive. With the help of the proposed model, quantitative and qualitative analysis of electromagnetic and electromechanical processes in transient and established modes of operation, research of dynamic mechanical and operational characteristics, analysis of spectral composition and hodographs of spatial vectors of phase voltage and current of an АМ can be carried out. The considered model can be applied not only when powering an asynchronous motor from a three-phase source with a sinusoidal form of voltage, but also when powering it from power semiconductor converters. The scheme of a virtual installation for modeling and researching processes in a three-phase АМ with a short-circuited rotor was developed in the work. The analyzed installation includes the following blocks: three-phase AC voltage source, three-phase AC voltage meter, Selector block, Voltage Measurement block, three-phase АМ under investigation, static torque assignment block, active and reactive power meter, Subsystem block. An analysis of electromagnetic processes in static and electromechanical converters of electrical energy was carried out using the spatial vector method, which has found wide use. With the help of software packages, instantaneous values of symmetrical three-phase variables such as voltage, current, flux linkage were mathematically transformed into one vector.

On the generation of frequency combs based on mechanical vibrations of 2D material nanosheets

We study the nonlinear dynamics of a rectangular atomically thin nanostrip under conditions of internal combinational resonance between two transverse and one longitudinal modes of mechanical vibrations. Conditions have been analytically found for the initial pretension of the layer required to realize resonance between eigenforms with given indices of variability along the length. It is shown that under conditions of internal resonance, a nonlinear mode of free oscillations is excited in the system, the spectrum of which has the form of a frequency comb. Two qualitatively different types of oscillations of this kind are identified – those caused by the initial excitation in the working longitudinal form of oscillations and in two transverse forms. A significant dependence of the spectral composition of the generated frequency combs on the relationships between the amplitudes of the initial disturbance for the three interacting modes and on the value of the internal frequency detuning parameter of the system is shown.

Towards using virtual acoustics for evaluating spatial ecoacoustic monitoring technologies

Abstract Small microphone arrays and sound‐source localisation algorithms are increasingly prevalent in the passive acoustic monitoring (PAM) of ecosystems. These technologies enable analysis of natural soundscapes' spatial features, yielding additional insights into biodiversity and ecosystem health. While many of these technologies have been evaluated in the field, there is a lack of controlled, repeatable methods to test them. We developed an ambisonic virtual sound environment (VSE) for simulating real natural soundscapes to evaluate spatial PAM technologies. We validated this novel approach using a PAM recorder with a six‐microphone array, from which we extracted a typical suite of ecoacoustic metrics, including acoustic indices and avian species predictions and localisations from the software BirdNET and HARKBird, respectively. We first verified whether the VSE could replicate natural soundscapes well enough to test PAM technologies by comparing these metrics between field and VSE‐based recordings. To pilot the VSE as an environment for testing PAM hardware, we assessed how orientation impacts the six‐microphone array's performance by using the same suite of metrics to compare VSE recordings made with the array at various pitch angles. Finally, we piloted the VSE as a test platform for PAM software by investigating how BirdNET and HARKBird perform on bird calls added to the VSE‐replicated soundscapes. While the VSE and field recordings had similarities in some metrics, including spectral composition and BirdNET predictions, ambisonics' perceptual bias and susceptibility to spatial aliasing limited the spatial analyses that could be undertaken. Our trials nonetheless revealed that device orientation impacts the performance of HARKBird and certain ecoacoustic indices, and that BirdNET and HARKBird perform best on louder, more directional bird calls. Our results demonstrate the potential for this approach, but highlight limitations to using an ambisonics‐based VSE. We thus provide guidelines for the use and refinement of such systems towards more standardised, controlled benchmarking of PAM technologies, empowering practitioners to make more informed decisions on using these vital tools.

The Environmental Light Characteristics of Forest Under Different Logging Regimes.

Light is a fundamental attribute and key abiotic driver in forest ecosystems. Although the ecological effects of light itself is well studied, capturing the complex parameters that constitute the whole light environment remain an intricate research endeavor. Here, we apply the newly introduced environmental light field (ELF) technique in Kibale National Park, Uganda. We captured whole light scenes with repeat photography and processed it to measure both the spectral composition of light in the red-green-blue range, as well as its variation, or "contrast-span", using the newly introduced International System of Units (SI); "lit". We compare across major and globally common utilized forest types-primary, secondary, and selectively logged areas, as well as a completely cleared area as a control. We find that the ELF system is able to effectively capture key aspects of the local light environment across the range of forest types. The distribution of light intensity and its spectral composition across our study is hardly uniform, with primary forest and a clearing showing two orders of magnitude difference in light. Blue light predominates the sky areas of the clearing, indicating the Rayleigh scattering of sunlight in the atmosphere. In general, radiance decrease with increasing intactness of the forest, and selectively logged and primary forest show the most similar environmental light characteristics. Owing to its ability to capture fine scale variations in light across elevation gradients, their spectral characteristics, as well as their intensities, the ELF system should become a useful tool in better quantifying light in ecology. In particular, we discuss its potential use in restoration ecology.

The Role of Glutamate Metabolism and the GABA Shunt in Bypassing the Tricarboxylic Acid Cycle in the Light.

Glutamate is an essential amino acid in both the energy and biosynthetic processes in plant cells. The aim of this work was to study changes in glutamate metabolism upon irradiation of maize (Zea mays L.) leaves with light of different spectral compositions, as well as to identify mechanisms regulating the work of enzymes involved in the studied process. A study was conducted of light-induced changes in glutamate metabolism in maize leaves, mediated by redirecting the glutamate flow to the γ-aminobutyric acid (GABA) shunt. Glutamate dehydrogenase (GDH) was more active in darkness, and the irradiation by red light inhibited the expression of both the Gdh1 and Gdh2 genes. EGTA and ruthenium red abolished the effects of light, indicating the participation of Ca2+ ions in phytochrome signal transduction. Contrary to GDH, glutamate decarboxylase (GAD) activity was moderately higher in the light, stimulated by red light, while far-red light reversed the effect. The effect of light on Gad expression was more pronounced than on GAD activity. Irradiation by red light also resulted in the increase in activity of GABA transaminase (GTA), which was abolished by far-red light. The third enzyme of the GABA shunt, succinic semialdehyde dehydrogenase (SSADH), was also activated by light. The effect of light on the expression of Ssadh1, but not on Ssadh2, was phytochrome-dependent. It is concluded that irradiation by light shifts glutamate metabolism from GDH to GAD with the activation of GABA transaminase and SSADH. This suggests that the GABA pathway plays a role in the maintenance of the tricarboxylic acid cycle in the light via bypassing its reactions when the 2-oxoglutarate dehydrogenase complex is inhibited and the cycle switches to the open mode.

O073 The effect of blue-enriched light in older adults with sleep disturbance on sleep and daytime performance: A randomised, placebo-controlled crossover trial

Abstract Introduction Light therapy is a non-pharmacological intervention for circadian and sleep disorders. However, there is limited evidence about the effect on electroencephalographic (EEG) sleep in older individuals with sleep disturbance. Methods Twelve participants (8 female; mean ± SD age, 65.6 ± 8.7 years) with self-reported poor sleep completed two randomly allocated 72-hour in-laboratory visits separated by 2 weeks. The intervention light condition consisted of blue-enriched light (melanopic EDI=843.6 lux) during the day and blue-depleted light (melanopic EDI=49.5 lux) 3-hours before lights out. The control light condition consisted of polychromatic light (melanopic EDI=215.8 lux) during the day and reduced light (melanopic EDI=60.8 lux) 3-hours before lights out. The primary outcome was wake after sleep onset (WASO), with secondary outcomes of sleep micro-architecture parameters (256-channel high-density EEG) and neurobehavioural performance. Results The intervention light did not improve WASO compared to the control (p=0.338) but there was a significant increase in N1 sleep (p=0.046). The only neurobehavioural difference was in Stroop text accuracy (2.2%, p=0.028). High-density EEG analysis showed the intervention light significantly increased sigma activity (12–16 Hz) in the frontal and parietal cortex during N2 sleep relative to control light (p=0.017). Conclusions Overall, blue-enriched light over three days did not improve EEG sleep (WASO) or neurobehavioural performances except for accuracy (Stroop) in older adults with sleep disturbance. Further research is required to determine the ideal intensity, spectral composition, duration and timing of blue-enriched lighting on objective sleep outcomes in individuals with poor sleep quality.

Luminescence of copper-doped α-quartz crystal after oxygen treatment

Treatment of copper-doped natural α-quartz in oxygen atmosphere at 1200 °C leads to changes in luminescence properties. The luminescence center of AlO4−-Cu+ is modified. The intensity is low in the annealed sample and increases after X-ray irradiation at 293 K. Annealing of the irradiated sample leads to a strong peak of thermally stimulated luminescence (TSL) at ∼500 K. Its spectral composition is mainly due to the AlO4−-Cu+ center. Irradiation of the sample treated with oxygen at 77 K gives a new TSL peak at ∼180 K and a peak at 244 K existing in the untreated sample. Both peaks were attributed to Cuo centers released from different sites and recombined with a hole in AlO4 having additional oxygen. The introduction of copper ions into quartz removes alkali metal ions and eliminates the corresponding luminescence, but after treatment in oxygen, luminescence with similar parameters is restored at low temperatures. In this case, only the glow of the AlO4−-Cu+ center is observed in the recombination luminescence (TSL and afterglow). Therefore, modification of the AlO4−-Cu + center with oxygen imparts to this center properties similar to the complex center AlO4− (K, Na or Li ion) with monovalent aluminum ions, although the alkali ions are replaced by copper ions. The oxygen-treated sample exhibits an increased efficiency of energy transfer by excitons to the luminescence center, measured as excitation spectra in the region of fundamental absorption of silicon dioxide. The X-ray excitation of the self-trapped exciton luminescence does not depend on oxygen treatment. Also, the spectra of intrinsic optical reflection and Raman scattering do not change compared to the untreated sample. The obtained result is interpreted as a modification of the defect by high-temperature treatment in oxygen.

Impact of light spectrum on outdoors tubular photobioreactors used for microalgae-based wastewater treatment

Microalgae-based wastewater treatment involves various factors, including algal ecosystems and environmental conditions. Light spectral composition, particularly wavelength and intensity, is a key but underexplored under out-of-laboratory conditions. Therefore, this study investigates the effects of different light wavelengths on microalgae in wastewater treatment systems using filtered sunlight. It examines critical physiological and biochemical processes in microalgae, including pigment synthesis, carbon fixation, and nutrient uptake. A tubular photobioreactor (PBR) setup with two diameters, 4-inch (10.16 cm) and 6-inch (15.24 cm), was tested outdoors for three months using blue, green, and red filters. These filters transmitted radiation and were transparent to infrared light, ranging from 750 nm to blue-green-infrared light (peaking at 450 nm), green-infrared light (peaking at 520 nm), and red-infrared light (peaking at 600 nm). The study analyzed 56 absorption curves, finding that light color influences microalgae physiology even under the same radiation levels. Pigment production was enhanced with only 10 % of total solar radiation, avoiding photoinhibition. Chlorophyll production was highest in the 4-inch PBR with a green filter, while blue light filters promoted pigment accumulation in 6-inch PBRs. However, the 6-inch reactors exhibited a lower growth rate compared to the 4-inch reactors, with significant effects of light color seen only at extreme irradiance levels. Larger diameter PBRs also increased the nitrification process, regardless of the filter used. These results have important implications for biofuel production, wastewater treatment, and bioremediation, underscoring the role of filtered light in enhancing microalgae performance in environments requiring deeper sunlight penetration.

Акустические эффекты на волноводных микроструктурах в кремнии

Basic waveguide structures in anisotropic monocrystalline silicon medium are investigated for the existence of localized acoustic modes. The geometries of the structures were determined by technological methods and the practice of anisotropic etching, which guarantees reproducible high-quality structures in terms of geometric and crystallographic parameters. The acoustic effects were modeled by semi-analytical finite element method in the problems on eigenvalues and on the response to a harmonic traction source. Edge and surface localized modes were found. The spectral composition of the localized modes was interpreted on the basis of the surface acoustic wave slowness curves. Pseudomodes, highly localized leakage waves, were detected in a number of considered structures. The obtained results allow to evaluate promising geometrical configurations for further detailed study of the complete scope of dispersion properties of both single waveguides and their finite set.

Vibrational noise disrupts Nezara viridula communication, irrespective of spectral overlap

Insects rely on substrate vibrations in numerous intra- and interspecific interactions. Yet, our knowledge of noise impact in this modality lags behind that in audition, limiting our understanding of how anthropogenic noise affects insect communities. Auditory research has linked impaired signal perception in noise (i.e., masking) to spectral overlap. We investigated the impact of noise with different spectral compositions on the vibrational communication of the stink bug Nezara viridula, examining courtship behaviour and signal representation by sensory neurons. We found negative effects of vibrational noise regardless of spectral overlap, challenging common expectations. Noise impaired the ability of males to recognize the female signal and localise its source: overlapping noise decreased sensitivity of receptor neurons to the signal and disrupted signal frequency encoding by phase-locking units, while non-overlapping noise only affected frequency encoding. Modelling neuronal spike triggering in sensory neurons linked disrupted frequency encoding to interference-induced alterations of the signal waveform. These alterations also affected time delays between signal arrivals to different legs, crucial for localisation. Our study thus unveils a new masking mechanism, potentially unique to insect vibrosensory systems. The findings highlight the higher vulnerability of vibration-mediated behaviour to noise, with implications for insect interactions in natural and anthropogenically altered environments.

Cochlear Implant Sound Quality.

The aims of this exploratory study were (a) to assess common terms used to describe cochlear implant (CI) sound quality by patients fit with conventional CIs and (b) to compare those descriptors to previously obtained acoustic matches to CI sound quality created by single-sided deaf (SSD) patients for their normal-hearing ear. CI patients fit with Advanced Bionics (AB; n = 89), Cochlear Corporation (n = 86), and MED-EL (n = 80) implants were the participants. The patients filled out a questionnaire about CI sound quality for two time points: For the time near activation (T1) from memory and at the time of filling out the questionnaire (T2). The mean CI experience at T2 for the three groups ranged from 4 to 8 years. The questionnaire was composed of 25 adjectives describing sound quality. For T1, the most commonly used descriptors were Computer-like, Treble-y, Metallic, and Mickey Mouse-like. A superordinate category of HiPitched (High Pitched) gathered significantly more responses from patients with shorter electrode arrays (AB and Cochlear) than patients with longer arrays (MED-EL). At T2, the most common descriptor was Clear and was chosen by approximately two thirds of the patients. The between-group differences in responses to items in the HiPitched category, present at T1, were absent at T2. The questionnaire data from conventional CI patients differs from previous sound matching data collected from SSD-CI patients. Alterations to the spectral composition of the signal are less salient to experienced conventional patients than to experienced SSD-CI patients. This is likely due to the absence, for conventional patients, of an exemplar in an NH ear against which to judge CI sound quality.

Вплив червоного та синього електромагнітного випромінювання на каталазну активність зародків в’юна Misgurnus fossilis L.

Photobiomodulation therapy is widely used to treat various pathological conditions. This therapy is based on the use of monochromatic light radiation. The light of the visible spectrum induces different biological effects at the molecular and cellular levels, both therapeutic and toxic. The obtained effect depends on the length of radiation, exposure, etc. One of the possible mechanisms of such influence is the regulation of pro-oxidant-antioxidant homeostasis. In order to clarify the mechanism of action of electromagnetic radiation (EMR) of different spectral composition, catalase (CAT) activity was investigated in germ cells of loach Misgurnus fossilis L. during embryogenesis. Since, loach embryos are an adequate system that reflects the physiological state of the cell both under normal conditions and as a result of the influence of various pharmacological, physical and chemical agents. The resulting zygotes were irradiated (10 min) with blue and red LEDs (λ = 460 and 660 nm, respectively). The activity of CAT was determined by the ability of hydrogen peroxi­de to form a stable colored complex with molybdenum salts. It was established that EMR of the red spectrum has the most pronounced biological effects and caused significant changes in catalase activity during embryogenesis relative to control and blue light. The maximum increase of the indicator occurs at the stage of 16 blastomeres, and at the stage of 8 and 10 divisions, a gradual decrease in enzymatic activity is observed. Irradiation by the light of the blue spectrum lasting 10 min did not cause significant changes in catalase activi­ty relative to the control at the early stages of loach embryogenesis. The obtained results suggest that CAT, one of the key enzymes of the antioxidant defense system, undergoes photoactivation under the influence of red light.

Lipid Fatty Acid Profile of Asplenium scolopendrium Gametophytes Modulated by Light Spectral Composition.

We investigated the total lipid fatty acid (FA) composition of the fern Asplenium scolopendrium gametophyte, representing 25 individual FA species, for the first time. Conjugated octadecadienoates-18:2(10,12), rarely found in plant tissues-were identified. The possibility of modulating the lipid FAs composition under the action of light of different wavelengths on in vitro cultured gametophytes was demonstrated. Thus, exposure to blue (450nm) and red (660nm) light resulted in only insignificant changes in the minor FAs. This stability can be attributed to the fact that these wavelengths of light are necessary for photosynthesis and therefore optimal for the fern gametophyte. Green (GL, 525nm) and far-red (FRL, 730nm) light caused dramatic changes in the FA profile-the triene FAs decreased and the very-long-chain (VLC) FAs increased, mainly at the expense of saturated even-VLCFAs. This resulted in a dramatic decrease in the unsaturation index, indicating a decrease in membrane fluidity under GL and FRL illumination conditions. These changes indicate a significant rearrangement of the lipid metabolism of the A. scolopendrium gametophyte at light wavelengths not directly involved in photosynthetic processes (GL and FRL), in particular by triggering β-oxidation and blocking the plastidial pathway of FA synthesis.

Shrink effects on nanoscale MOS capacitor in visible and NIR spectral Ranges

This research explores the influence of visible and near-infrared light on the electrical characteristics of nanoscale MOS capacitors, examining the effects of light intensity and spectral composition. Photon absorption within the device stimulates an enhancement of the inversion electron layer. A spectral analysis encompassing the ultraviolet to near-infrared range (400–1100 nm) is presented. Research on nanoscale devices of this nature can contribute to a profound understanding of fundamental light-matter interactions at the atomic and molecular scale. This knowledge can pave the way for the development of novel optoelectronic coupled devices, which combine light trigger and electronic functionalities. These devices, when integrated in Photonics Integrated Circuits (PICs), could have applications in areas such as solar cells, photodetectors, and future ultrasmall electronic components.

Ідентифікація одиночного турбулентного газового факелу засобами й методами комп’ютерного зору в імітаційній установці топки котлоагрегата

The issue of optimizing the combustion process is quite relevant for modern thermal power engineering and arises even more in the context of the restoration and reconstruction of the energy infrastructure of Ukraine. The use of computer vision tools will allow directly determining the qualitative characteristics of the gas combustion process in real time without relying on measurements of secondary parameters, the change in values ​​of which is quite inertial. The process of turbulent torch combustion itself, which occurs in industrial boiler units, is poorly studied and does not allow for its modeling in advance. Therefore, an important stage in the construction of any control and management system is the identification of the object by conducting experimental measurements, on the basis of which the parameters and forms of dependencies will be determined to obtain a mathematical model of the process. In the course of the current work, the process of identifying the methane torch combustion process inside the simulated installation of the boiler unit furnace (combustion chamber) is considered. According to the results of a series of experiments, it was possible to obtain the dependences of the characteristics of the visual manifestation of the combustion process, recorded by a video camera, on its current combustion mode, which was determined by the satisfaction of the stoichiometric ratio of gas and air supply to the burner with preliminary mixing of the gas-air mixture. In general, the dependences of the spectral composition of the radiation, the area of ​​the torch and its luminosity on the combustion mode were obtained. The dependences are characterized by significant nonlinearity when the torch transitions to the mode of significant chemical underburning, but are easily linearized in the area of ​​interest, which is located near the point of satisfaction of the stoichiometric ratio. The results of this article demonstrate the suitability of the parameters obtained by computer vision for their use in traditional control systems. Taking into account the speed of obtaining such data, we can conclude that it is appropriate to create a control system based on combustion parameters completely obtained by computer vision methods and means.

Spectral absorbance changes in the photoreceptors of the juvenile masked greenling, Hexagrammos octogrammus (Pisces, Hexagrammidae).

When changing habitat during migration or ontogenesis, fish encounter changes of the visual environment, among which the most important is the spectral composition of light and turbidity. This leads to changes in the behavior, morphology, and physiology of the visual system, in particular, spectral sensitivity, which is determined by the properties of visual pigments. The masked greenling Hexagrammos octogrammus has an additional factor that shapes effective spectral sensitivity-the presence of densely bright orange cornea which reversibly changes its density depending on the state of light/dark adaptation. However, it is unknown to what extent the properties of visual pigments are matched to spectral properties of the developing cornea at the final stage of metamorphosis during migration of juveniles from pelagic to coastal environments. The findings of this microspectrophotometric study show that the range of the spectral sensitivity of rods and cones in juveniles is much wider than in adults, with a shift in the sensitivity of a significant part of the cells to shorter wavelengths. The reason for this is the large variation in the ratio of chromophores A1:A2 in the pigment mixture in each cell and possible expression of new opsins. This also indicates the asynchrony of pigment transformations in different types of photoreceptors and the incompleteness of these transformations on the eve of the transition to bottom life in shallow water.

Color‐Accurate Camera Capture with Multispectral Illumination and Multiple Exposures

AbstractCameras cannot capture the same colors as those seen by the human eye because the eye and the cameras' sensors differ in their spectral sensitivity. To obtain a plausible approximation of perceived colors, the camera's Image Signal Processor (ISP) employs a color correction step. However, even advanced color correction methods cannot solve this underdetermined problem, and visible color inaccuracies are always present. Here, we explore an approach in which we can capture accurate colors with a regular camera by optimizing the spectral composition of the illuminant and capturing one or more exposures. We jointly optimize for the signal‐to‐noise ratio and for the color accuracy irrespective of the spectral composition of the scene. One or more images captured under controlled multispectral illuminants are then converted into a color‐accurate image as seen under the standard illuminant of D65. Our optimization allows us to reduce the color error by 20–60% (in terms of CIEDE 2000), depending on the number of exposures and camera type. The method can be used in applications in which illumination can be controlled, and high colour accuracy is required, such as product photography or with a multispectral camera flash. The code is available at https://github.com/gfxdisp/multispectral_color_correction.

Tactile sensitivity to missing tones in complex vibrotactile signals.

Haptic interactions with objects induce complex vibrotactile signals that are central to tactile perception. Despite the broad literature on vibrotactile perception, surprisingly little is known about the sensory processing of complex tactile signals made of multiple pure tones. To fill this gap, the study reported here investigated the impact of the constitutive pure tones of a complex vibrotactile signal on its perception. Participants completed a three-alternative forced choice (3-AFC) task in which they were asked to identify an odd signal among two complex references. The odd signal was created by removing one pure tone from the reference, which varied in spectral composition, harmonicity, and interfrequency intervals. Each reference signal was made of either two, three, or four pure tones. The results revealed that the removed pure tone's value as well as the interfrequency interval play a significant role in participants' performance whereas changes in harmonicity and complexity have little impact. The smaller the ratio between the removed frequency and the lowest one of the reference signals, the better the participants' capacity to identify the signal with the missing tone. As this ratio correlates with that of pure tone's perceived intensity, participants' performance can be linked to either of them. Analysis of a subset of complex signals made of pure tones perceived with roughly equal intensity showed that the correlation still holds but slightly decreases. Overall, these results suggest that perception of complex vibrations might be mediated by tactile mechanisms related to both frequency selectivity and pure tones' perceived intensity.NEW & NOTEWORTHY This research investigates the respective roles of frequency range, harmonicity, and complexity on human perception of vibrotactile signals. The results revealed that only pure tones that are close to the lower frequencies of the complex vibration are noticed when they are missing. This finding sheds new light on the mechanisms underlying the tactile perception of complex vibrations.

Correction: Agroforestry versus agrivoltaic: spectral composition of transmitted radiation and implications for understory crops

Correction: Agroforestry versus agrivoltaic: spectral composition of transmitted radiation and implications for understory crops