Mid Frequency Research Articles

Profiling Word Frequency and Readability of Online Learner Dictionary Definitions

This study examined 283 online learner dictionary definitions in terms of scores based on word frequency level and readability. Results revealed three findings. First, in terms of word frequency levels, definitions from the Cambridge learner dictionary incorporated fewer non-high frequency words (mid and low frequency words) compared to Oxford, Dictionary. com and Collins COBUILD learner dictionaries. Second, in terms of readability, definitions from the Random House learner dictionary were written at a significantly higher grade level compared to the other six online learner dictionaries. Third, in terms of both level of frequency words incorporated into definitions and readability grade level definitions, the Cambridge, Merriam-Webster and Longman online learner dictionaries were easier to understand compared to online learner dictionaries from Dictionary.com, Collins COBUILD, Oxford and Random House. Overall, the findings suggest both word frequency level and readability might contribute to the difficulty of online learner dictionary definitions.

SRR inspired modified psi shaped perfect metamaterial absorber for C-band application

In this research article, a compact and simple design of polarization insensitive perfect metamaterial absorber (PMA) is offered. The design is optimized to target the two mid frequencies of C-band for satellite communication. This novel design is a congress of two modified psi shaped resonators which are surrounded by a split ring resonator (SRR) and an octagonal split ring resonator (OSRR). Dielectric material FR-4 of loss tangent 0.025 and thermal conductivity 0.3 WK-1m−1 is used as substrate whereas the copper (annealed) of thermal conductivity 401 WK-1m−1 and electrical conductivity 5.8 × 107 Sm−1 is used for back copper plate and resonators. This is a compact unit cell of electrical dimension 0.268λ × 0.268λ with 1.6 mm thickness of dielectric substrate and 0.035 mm thickness of bottom copper sheet. The proposed PMA is simulated within the microwave frequency range 5 GHz to 10 GHz with commercially available FIT based high-performance3D EM analyserCST microwave studio suite. The simulation result yields two resonance peaks at 6.15 GHz and 7.36 GHz with fantastic absorption rate 99.99% and 99.40%, respectively. The presented PMA shows polarization insensitivity up to 45° and oblique wide angle incidence up to 75°. Moreover, the simulated outcome is validated by some trusted validation processes; for example- equivalent LC circuit by advanced design software (ADS) and FEM based high-frequency structure simulator (HFSS). A very negligible amount of deviation of resonance frequencies are observed in ADS and HFSS results compared to CST simulated result. Different types of array combinations are also simulated to test the stability of the result and to check the coupling effect. This C-band PMA is recurrently deployed in satellite communication band, defense, security, and stealth coating equipment.

Direct Fabrication of a Copper RTD over a Ceramic-Coated Stainless-Steel Tube by Combination of Magnetron Sputtering and Sol–Gel Techniques

Reducing the economic and environmental impact of industrial process may be achieved by the smartisation of different components. In this work, tube smartisation is presented via direct fabrication of a copper (Cu)-based resistive temperature detector (RTD) on their outer surfaces. The testing was carried out between room temperature and 250 °C. For this purpose, copper depositions were studied using mid-frequency (MF) and high-power impulse magnetron sputtering (HiPIMS). Stainless steel tubes with an outside inert ceramic coating were used after giving them a shot blasting treatment. The Cu deposition was performed at around 425 °C to improve adhesion as well as the electrical properties of the sensor. To generate the pattern of the Cu RTD, a photolithography process was carried out. The RTD was then protected from external degradation by a silicon oxide film deposited over it by means of two different techniques: sol–gel dipping technique and reactive magnetron sputtering. For the electrical characterisation of the sensor, an ad hoc test bench was used, based on the internal heating and the external temperature measurement with a thermographic camera. The results confirm the linearity (R2 > 0.999) and repeatability in the electrical properties of the copper RTD (confidence interval < 0.0005).

Sound Isolation Performance Assessment of Traditional and Retrofitted Timber-Framed Dwellings

This study focuses on sound isolation performances of original timber-framed interior wall and floor components in traditional-framed dwellings in Turkey and 19th century mud-brick samples used as infill within the timber frame. The acoustical ramifications of some retrofits proposed in the contexts of minimum intervention and refunctioning the traditional dwellings are assessed in reference to the relevant standards. Field measurements show that sound isolation performances of the original timber-framed wall and floor are ineffective. The results of this study show that acoustical retrofits applied on the original wall keeping its wood lath and mud-brick infill are about 5–7 dB in the weighted sound reduction index (RW) and are more effective than those applied on the reconstructed wall. Sound transmission loss values of 50- and 100-mm-thick authentic mud samples are 22–38 and 30–43 dB, respectively, between 125 and 4,000 Hz. The sound absorption coefficient at mid frequencies and the noise reduction coefficient of 50-mm-thick mud samples are 0.28 and 0.23, respectively. These results signal the importance of keeping traditional construction techniques of wall and floor during retrofits to improve the sound isolation performance. Adobe mixtures similar to the 19th-century mud-bricks can be of guidance for the production of innovative soundproofing earth-based building materials.

Statistical energy analysis simulation of an air-handling cabinet

Statistical energy analysis (SEA) is a vibro-acoustic modeling technique suitable for systems where high modal densities exist. Traditionally SEA is used for predicting system response in higher frequency bands. However, for systems such as an air-handler that contain large, flat panels constructed of sheet metal the usefulness of SEA stretches into mid and lower frequency bands as well. Measured results of an air-handling cabinet were obtained by spatially averaging accelerations of cabinet surfaces caused by an input of white noise into the cabinet side by a shaker. Energy from each sub-panel of the cabinet was normalized with the panel into which the energy was input for easy comparison with modeled data. A simplified model of the air-handling cabinet processed in VA One software yielded results generally within 10 dB of measured results. Some lower frequency band limitations were realized due to cabinet geometry and construction. These results focus primarily on the structure and less so on the acoustic volume of the air-handling cabinet.

Tuning the characteristics of Al2O3 thin films using different pulse configurations: Mid-frequency, high-power impulse magnetron sputtering, and their combination

The growth of alumina (Al2O3) films by reactive magnetron sputtering in oxidizing atmosphere is complicated due to the difficulty to keep the process stable within the transition zone and the formation of insulating layers on the target, which may lead to arcing events. To minimize those issues, an active feedback reactive sputtering control was explored to deposit Al2O3 thin films by two sputtering sources: high-power impulse magnetron sputtering (HiPIMS) and mid-frequency (MF) at three different powers (2000, 2500 and 3500 W) and two deposition temperatures (200 and 450 °C). A combination of MF + HiPIMS at 2500 W was also studied. X-ray diffraction (XRD) revealed the formation of γ-Al2O3 polycrystalline films, except those deposited at 200 °C, which were amorphous. In fact, more energetic depositions (higher power, use of HiPIMS instead MF) lead to films with larger grain density and refractive index, up to values close to α-Al2O3. HiPIMS deposition induced films with higher values of compressive stress than MF, which is caused by the higher energy and intensity of the ions impinging on substrate and its lower deposition rate. The combination of MF + HiPIMS led to higher deposition rates, lower compressive stress, and lower crystallinity compared with HiPIMS alone.

Applying vertical greening systems to reduce traffic noise in outdoor environments: Overview of key design parameters and research methods

Vertical greening can be used to absorb and scatter sound, which may reduce noise levels in street canyons. In this paper, a literature review is presented, which combines results and methods from over 40 individual studies. The article describes the guiding principles behind the acoustic effects of vertical greening and provides an overview of the prevalent research methods. The article shows that vertical greenery is effective for the reduction of mid and high frequency noise, unless air cavities or resonators are introduced inside, or behind, the systems. The review also reflects on studies with an emphasis on the application of vertical greenery in streets and urban blocks. The aim of the article is to set out the key design parameters for noise reduction that can be achieved by vertical greening, focusing on designers and engineers.

Capturing the power of seizures: an empirical mode decomposition analysis of epileptic activity in the mouse hippocampus.

Various methods have been used to determine the frequency components of seizures in scalp electroencephalography (EEG) and in intracortical recordings. Most of these methods rely on subjective or trial-and-error criteria for choosing the appropriate bandwidth for filtering the EEG or local field potential (LFP) signals to establish the frequency components that contribute most to the initiation and maintenance of seizure activity. The empirical mode decomposition (EMD) with the Hilbert-Huang transform is an unbiased method to decompose a time and frequency variant signal into its component non-stationary frequencies. The resulting components, i.e., the intrinsic mode functions (IMFs) objectively reflect the various non-stationary frequencies making up the original signal. We employed the EMD method to analyze the frequency components and relative power of spontaneous electrographic seizures recorded in the dentate gyri of mice during the epileptogenic period. Epilepsy was induced in mice following status epilepticus induced by suprahippocampal injection of kainic acid. The seizures were recorded as local field potentials (LFP) with electrodes implanted in the dentate gyrus. We analyzed recording segments that included a seizure (mean duration 28 s) and an equivalent time period both before and after the seizure. Each segment was divided into non-overlapping 1 s long epochs which were then analyzed to obtain their IMFs (usually 8-10), the center frequencies of the respective IMF and their spectral root-mean-squared (RMS) power. Our analysis yielded unbiased identification of the spectral components of seizures, and the relative power of these components during this pathological brain activity. During seizures, the power of the mid frequency components increased while the center frequency of the first IMF (with the highest frequency) dramatically decreased, providing mechanistic insights into how local seizures are generated. We expect this type of analysis to provide further insights into the mechanisms of seizure generation and potentially better seizure detection.

Effect of resistance exercise dose components for tendinopathy management: a systematic review with meta-analysis

ObjectiveTo investigate potential moderating effects of resistance exercise dose components including intensity, volume and frequency, for the management of common tendinopathies.DesignSystematic review with meta-analysis and meta-regressions.Data sourcesIncluding but not limited...

Aeroacoustic sources analysis of wake-ingesting propeller noise

High resolution aeroacoustic source analysis is a prerequisite to address the noise concerns and release the full benefits of wake-ingesting propellers. In this work, the aeroacoustic sources of a two-bladed propeller ingesting the wake of an aerofoil are investigated using large eddy simulation in conjunction with two different source identifying approaches. The first approach is the numerical beamforming that utilizes both the classical and wavelet-based beamforming techniques, which determine the phase variations of sources at the low to mid frequencies and reveal that the high-frequency sources are phase-independent. To further improve the spatial resolution of source identification, a new near-field aeroacoustic source analysis approach based on the acoustic analogy is developed in this work. In particular, the on-surface source terms emanating the far-field noise are derived based on the Ffowcs Williams and Hawkings equation for low Mach number flows and constant rotating propellers. Through the incorporation of the simulation results into the proposed source analysis approach, various types of aeroacoustic sources are identified and studied by visualizing their distributions on the propeller surfaces, correlating to flow features and examining the noise spectra and directivity. While the leading edge sources are highly correlated with the wake interaction process, the sources at the mid-chord and the trailing edge of the blade can maintain their strength across most revolving angles. Overall, the proposed analysis approaches extend the capability of computational fluid dynamics and enable the detailed study of noise generation mechanisms of wake-ingesting propeller noise.

Impact of Intraoperative Findings on Hearing in Revision Ear Surgery.

Hearing results after chronic ear surgery encompass recurrence, localization and extent of cholesteatoma, type of surgery, ossiculoplasty methods, but rarely interpret intraoperative findings. This study aimed to analyze the impact of intraoperative findings in revision tympanomastoidectomy in predicting postoperative hearing. This was a retrospective non-randomized cohort of 101 patients treated for recurrent chronic otitis media by tympanomastoidectomy. The patients' demographics, localizations of disease recurrence and perioperative hearing results were analyzed. Logistic regression showed that presence of tympanic perforation (p=0.036), ossicular chain damage (p=0.006), were negatively associated with improved hearing postoperatively. Attic cholesteatoma was associated with better postoperative hearing (p=0.045). Presence of tympanic perforation (p=0.050), alongside perifacial localization of imflammation (p=0.021) and ossicle destruction (p=0.013) were associated with worse postoperative hearing results. Multivariate analysis confirmed that tympanic perforation (p=0.040, F=4.401), and ossicular chain involvement (p=0.025, F=5.249), were consistent negative predictors of hearing improvement, while postoperative deterioration of hearing was associated with tympanic perforation (p=0.038, F=4.465) and facial nerve dehiscence (p=0.045, F=4.160). Comparison of postoperative revision tympanomastoidectomy hearing outcomes revealed significant positive reductions in air-bone gap values, primarily at low and mid frequencies. Postoperative hearing results at high frequencies are not affected by revision surgery.

Investigation of Machine Learning Model Flexibility for Automatic Application of Reverberation Effect on Audio Signal

This paper discusses an algorithm that attempts to automatically calculate the effect of room reverberation by training a mathematical model based on a recurrent neural network on anechoic and reverberant sound samples. Modelling the room impulse response (RIR) recorded at a 44.1 kHz sampling rate using a system identification-based approach in the time domain, even with deep learning models, is prohibitively complex and it is almost impossible to automatically learn the parameters of the model for a reverberation time longer than 1 s. Therefore, this paper presents a method to model a reverberated audio signal in the frequency domain. To reduce complexity, the spectrum is analyzed on a logarithmic scale, based on the subjective characteristics of human hearing, by calculating 10 octaves in the range 20–20,000 Hz and dividing each octave by 1/3 or 1/12 of the bandwidth. This maintains equal resolution at high, mid, and low frequencies. The study examines three different recurrent network structures: LSTM, BiLSTM, and GRU, comparing the different sizes of the two hidden layers. The experimental study was carried out to compare the modelling when each octave of the spectrum is divided into a different number of bands, as well as to assess the feasibility of using a single model to predict the spectrum of a reverberated audio in adjacent frequency bands. The paper also presents and describes in detail a new RIR dataset that, although synthetic, is calibrated with recorded impulses.

Basic Concept of the Beam Wave based Element for Mid and High Frequency Analysis

This paper describes a Hermite beam wave based element of the steady-state dynamic response of a 1D structure system. This study focuses on the development of beam wave based elements. Compared with standard piecewise polynomial approximation, the wave basis is shown to give a considerable reduction in computational degrees of freedom. In practical terms, it is concluded that the degrees of freedom for which accurate results can be obtained, using these new techniques, can be up to half of that of the conventional finite-element method.

COPD and 20-year hearing decline: The HUNT cohort study

BackgroundWe aimed to assess the association between chronic obstructive pulmonary disease (COPD) and long-term hearing decline. A further aim was to study sex differences. MethodsPopulation-based cohort study in Norway (the HUNT study) with baseline measurements in 1996–1998 and follow-up in 2017–2019. The sample included 12,082 participants (43% men, mean age at follow-up 64 years). We used multiple linear regression to assess the association between COPD (minimum one registered ICD-10 code with emphysema or other COPDs during follow-up) and 20-year hearing decline in the low/mid/high frequency area (0.25–0.5/1–2/3-8 kHz). We adjusted for age, sex, education, smoking, noise exposure, ear infections, hypertension and diabetes. ResultsPersons registered with COPD (N = 403) had larger 20-year hearing decline at low frequencies (1.5 dB, 95% confidence interval (CI) 0.6–2.3) and mid frequencies (1.2 dB, 95% CI 0.4–2.1), but not at high frequencies. At high frequencies, the association was stronger and statistically significant only among women (1.9 dB, 95% CI 0.6–3.2). Persons registered with both COPD and respiratory failure (N = 19) had larger 20-year hearing decline at low and mid frequencies: 7.4 dB (95% CI 3.6–11.2) and 4.5 dB (95% CI 0.7–8.4), respectively. ConclusionOur large cohort study shows an association between COPD and increased long-term hearing decline. Women seem to be more susceptible to COPD-related hearing loss at high frequencies. The findings support that COPD can affect the cochlear function.

Aided Cortical Auditory Evoked Potentials in Infants With Frequency-Specific Synthetic Speech Stimuli: Sensitivity, Repeatability, and Feasibility.

The cortical auditory evoked potential (CAEP) test is a candidate for supplementing clinical practice for infant hearing aid users and others who are not developmentally ready for behavioral testing. Sensitivity of the test for given sensation levels (SLs) has been reported to some degree, but further data are needed from large numbers of infants within the target age range, including repeat data where CAEPs were not detected initially. This study aims to assess sensitivity, repeatability, acceptability, and feasibility of CAEPs as a clinical measure of aided audibility in infants. One hundred and three infant hearing aid users were recruited from 53 pediatric audiology centers across the UK. Infants underwent aided CAEP testing at age 3 to 7 months to a mid-frequency (MF) and (mid-)high-frequency (HF) synthetic speech stimulus. CAEP testing was repeated within 7 days. When developmentally ready (aged 7-21 months), the infants underwent aided behavioral hearing testing using the same stimuli, to estimate the decibel (dB) SL (i.e., level above threshold) of those stimuli when presented at the CAEP test sessions. Percentage of CAEP detections for different dB SLs are reported using an objective detection method (Hotellings T 2 ). Acceptability was assessed using caregiver interviews and a questionnaire, and feasibility by recording test duration and completion rate. The overall sensitivity for a single CAEP test when the stimuli were ≥0 dB SL (i.e., audible) was 70% for the MF stimulus and 54% for the HF stimulus. After repeat testing, this increased to 84% and 72%, respectively. For SL >10 dB, the respective MF and HF test sensitivities were 80% and 60% for a single test, increasing to 94% and 79% for the two tests combined. Clinical feasibility was demonstrated by an excellent >99% completion rate, and acceptable median test duration of 24 minutes, including preparation time. Caregivers reported overall positive experiences of the test. By addressing the clinical need to provide data in the target age group at different SLs, we have demonstrated that aided CAEP testing can supplement existing clinical practice when infants with hearing loss are not developmentally ready for traditional behavioral assessment. Repeat testing is valuable to increase test sensitivity. For clinical application, it is important to be aware of CAEP response variability in this age group.

Analysis and Experimental Investigation of Sound Absorbing Materials for Industrial Noise Control

Abstract These days, noise pollution is a major issue that affects the environment. The high amount of noise present in the industries has adverse impact on the workers, operators and people associated in those fields. The consequences could be as hazardous as heart attack or even lifelong hearing loss. Sound absorption through barriers, mufflers are some popular fields of study. Some natural extracted materials show impressive SAC at lower and mid frequencies. Moreover, natural materials usage in this field is being popular as they emit almost zero amount of greenhouse gases and their manufacturing process requires a little amount of energy to process for ready to usage. A galvanized steel pipe as the impedance tube was chosen because it is cheaper than the impedance tube available in the market. We have tried to measure sound absorption coefficient of some combinations of different materials as an acoustic barrier material.

Effects of visual information on the face masked speech communication in Covid-secure classrooms

Acoustical measurements and speech intelligibility tests were carried out to investigate the effects of masks on speech communication experienced in real Covid-secure university classrooms during the pandemic. Face-masked speech levels and noise levels were measured to understand the acoustical effects of masks on speech sounds during 15 multiple lectures in 3 university classrooms. The speech intelligibility scores were also evaluated for lower and higher SNR (signal-to-noise ratio) conditions, and for with and without the presence of visual information conditions to investigate the effects of both the acoustic and visual signals in understanding speech communication in actual classroom situations. In the 3 active university classrooms the students experienced on average: speech levels of 55.1 dBA (σ = 5.5 dBA), noise levels of 42.3 dBA (σ = 3.9 dBA), and a speech-to-noise ratio of 12.8 dBA σ = 5.2 dBA). The mean SNR values at the listener’s position for the 15 lectures varied from 3.6 dBA to 20.0 dBA. The use of a portable sound amplification system increases the face-masked speech levels mostly at mid and high frequencies (500–4 kHz), thus it can be more useful for achieving higher SNR values in classrooms. The presence of visual cues have little effect on achieving more higher speech intelligibility scores in higher SNR conditions. The present results show that visual obstruction of the talker’s mouth decreases speech intelligibility scores by a maximum of 10% in lower SNR conditions, particularly at a SNR of 6 dBA or lower.

Can elastic waveform inversion benefit from inverting multicomponent data?

Waveform inversion aims to retrieve high-resolution earth parameter volumes. Due to its high computational cost, acoustic approaches using low to mid seismic data frequencies are often applied in velocity model building. However, in the presence of large parameter contrasts, an elastic formulation should be preferred due to wave interferences that limit the applicability of phase- and kinematics-only approaches. The benefits of elastic waveform inversion have been demonstrated with inversion of hydrophone data in marine environments. Here, we extend the approach to inversion of the vertical geophone component. We propose a weighted cost function in the waveform inversion algorithm to jointly invert multicomponent data sets, and we compare the results to the inversion of single-component data. For this study, we use an ocean-bottom-node data set from the deepwater Gulf of Mexico around a salt dome. We show that slightly different velocity models, reverse time migration images, and angle gathers are retrieved when using hydrophone or vertical geophone data, further improving either the shallow or deeper sediments. The joint inversion combines the improvements brought by the single-component inversions. Though it doubles the cost, joint elastic waveform inversion of hydrophone and vertical geophone data can help velocity model building around salt bodies.

Numerical Investigation on the Temperature dependent Impedance Characteristics of Far-Infrared Quantum Cascade Lasers

Quantum Cascade Lasers (QCLs) as Terahertz (THz) frequency sources offer a potentially viable solution for new applications in mid and far-infrared frequency bands. This research work exhaustively investigates the temperature dependence on the impedance of temperature dependent Quantum Cascade Lasers (QCLs) operating at 116μm, for the first time. In the 90-stage QCL considered for the work, the cold finger temperature is varied from 15K to 45K. When the device is biased at 0.6A current along with a cold finger temperature of 45K, the magnitude of intrinsic impedance was found to be 23.91mΩ, at a frequency of 4GHz. As the cold finger temperature is increased from 15K to 45K, the impedance response of the device becomes flat and stays constant. At 45K with an injected current of 1.5A, maximum impedance of 3.1mΩ is obtained. The resonant frequency characteristics of the device increase with increase in injected current and cold finger temperature. Also, it is observed that the magnitude of intrinsic impedance decreases with increase in injected current. The impact of cold finger temperature on the intrinsic impedance characteristics are detailed for prospective Radio over Fiber (RoF) applications.

Experimental subjective and objective analysis of speech intelligibility and acoustic comfort conditions in an unchanged XVII century Italian church

Listening conditions are a usual topic for places of worship. Santa Maria della Consolazione in Todi is one of the few examples of worship spaces in quasi-unchanged condition since its construction in 1607, and it offers the opportunity to study the acoustics that existed during the Counter-Reformation. Some of the most famous Italian architects worked on this project, and an apparent lack of consideration for acoustic comfort within the enclosed space was the reason for investigating its T30, C50, and STI parameters according to ISO 3382:1-2009 and IEC 60268-16. The measurements showed uncomfortable speech listening conditions (T30 = 9 s at 500 Hz, C50 = -8.6 dB at mid frequencies, average STI = 0.34) and were compared with other acoustic comfort conditions studies from the literature. To ensure the usefulness of using these standards, the study was contextualized with the original form of speech from the Tridentine Missal, which was chosen for its organisation and rigour. The most significant phrase that has to be heard from the assembly was selected, and listening tests were performed in order to assess acoustic comfort and to match the results with the analysis output following the standards. Despite the bad results of the measurements according to the Standards, the listening tests results showed adequate acoustic behaviour due to the contextualization of the rite inside the church. Furthermore, potential advantages of the original Latin text over a modern Italian translation were spectrally and phonetically demonstrated.