Narrow Frequency Band Research Articles

Vibration control of offshore wind turbines with a novel energy-adaptive self-powered active mass damper

Slender and flexible offshore wind turbines (OWTs) are vulnerable to external dynamic excitations, and passive tuned mass dampers (TMDs) have been widely used to control excessive vibrations of OWTs under harsh marine environments (e.g., strong winds and irregular sea waves). However, TMDs are only effective in the vicinity of the controlled frequency, i.e., in a narrow frequency band. Compared to passive TMDs, active control methods are normally considered to possess better control performances but at the cost of a large amount of external energy input. To this end, the present study proposes a novel energy-adaptive self-powered active mass damper (SPAMD) to mitigate the responses of OWT towers. The proposed control device can harvest energies from OWTs and then use them as the power to drive an active mass damper for structural vibration control. Specifically, a representative OWT is selected as a prototype structure and its tower is modeled as a multi-degree-of-freedom system by simplifying the rotor-nacelle assembly as a lumped mass and moment of inertia. The dynamic characteristics (mainly natural frequency and mode shape) of the tower obtained by the developed model are validated against a finite element model. Subsequently, the system configuration and working mechanism of SPAMD are introduced and SPAMD is incorporated into the developed model to simultaneously harvest energy and mitigate the fore-aft responses of the tower under wind and sea wave loads. The control effectiveness of SPAMD is further compared to the traditional TMD. Results show that SPAMD has a superior effect over TMD in controlling OWT responses.

Continuous sound from a marine vibrator causes behavioural responses of free-ranging, spawning Atlantic cod (Gadus morhua)

Marine vibrators are a new technology being developed for seismic surveys. These devices can transmit continuous instead of impulsive sound and operate over a narrower frequency band and at lower peak pressure than airguns, which is assumed to reduce their environmental impacts. We exposed spawning Atlantic cod (Gadus morhua) to sound produced by a prototype, but full-scale, marine vibrator, and monitored behavioural responses of tagged cod using acoustic telemetry. Fish were exposed to 10 × 3 h continuous sound treatments over a 4-day period using a randomised-block design. Sound exposure levels were comparable to airgun exposure experiments conducted previously with the same set-up ranging from ∼115 to 145 dB re 1 μPa2s during exposure. Telemetry data were used to assess 1) whether marine vibrator exposure displaced cod from the spawning ground, through estimation of residence and survival probabilities, and 2) fine-scale behavioural responses within the test site, namely swimming depth, activity levels, displacement, and home ranges. Forty-two spawning cod were tagged prior to the exposure, with 22 present during the exposure. All 22 tags were equipped with pressure sensors and ten of these additionally with accelerometers. While no premature departure from the spawning site was observed, cod reacted to the exposure by decreasing their activity levels (by up to 50%, SE = 7%) and increasing their swimming depth (by up to 2.5 m, SE = 1.0 m) within the test site during the exposure period. These behavioural responses varied by sex and time of day. Cod reactions to a marine vibrator may be more pronounced than reactions to airguns, possibly because continuous sound is more disturbing to fish than intermittent sound at the same exposure levels. However, given sample size limitations of the present study, further studies with continuous sound are necessary to fully understand its impact and biological significance.

Earthquake or blast? Classification of local-distance seismic events in Sweden using fully connected neural networks

SUMMARY Distinguishing between different types of seismic events is a task typically performed manually by expert analysts and can thus be both time and resource expensive. Analysts at the Swedish National Seismic Network (SNSN) use four different event types in the routine analysis: natural (tectonic) earthquakes, blasts (e.g. from mines, quarries and construction) and two different types of mining-induced events associated with large, underground mines. In order to aid manual event classification and to classify automatic event definitions, we have used fully connected neural networks to implement classification models which distinguish between the four event types. For each event, we bandpass filter the waveform data in 20 narrow-frequency bands before dividing each component into four non-overlapping time windows, corresponding to the P phase, P coda, S phase and S coda. In each window, we compute the root-mean-square amplitude and the resulting array of amplitudes is then used as the neural network inputs. We compare results achieved using a station-specific approach, where individual models are trained for each seismic station, to a regional approach where a single model is trained for the whole study area. An extension of the models, which distinguishes spurious phase associations from real seismic events in automatic event definitions, has also been implemented. When applying our models to evaluation data distinguishing between earthquakes and blasts, we achieve an accuracy of about 98 per cent for automatic events and 99 per cent for manually analysed events. In areas located close to large underground mines, where all four event types are observed, the corresponding accuracy is about 90 and 96 per cent, respectively. The accuracy when distinguishing spurious events from real seismic events is about 95 per cent. We find that the majority of erroneous classifications can be traced back to uncertainties in automatic phase picks and location estimates. The models are already in use at the SNSN, both for preliminary type predictions of automatic events and for reviewing manually analysed events.

Active vibration isolation by emulating the inerter through relative acceleration feedback

This study focuses on the realisation of a small-scale inerter by relative acceleration feedback and its use to isolate vibration. Two accelerometers attached to the two mechanical terminals of an electrodynamic force actuator are used to obtain the relative acceleration signal. This signal is then amplified by a constant gain and fed back to the two electrical terminals of the electrodynamic actuator as a voltage command. This sensor-actuator system is coupled to a two Degree-Of-Freedom (DOF) mechanical oscillator to study the feedback loop’s stability and the maximum achievable inertance effect. A fully coupled simulation model including the dynamics of the two inertial accelerometers and the electrodynamic actuator is developed. It is shown that, because of the active control system emulating an inerter, an antiresonance appears in the transfer admittance function of the two DOF mechanical system. Therefore, significant vibration isolation effect can be achieved in the narrow frequency band around the antiresonance. The antiresonance frequency is easily tuned by adjusting the feedback gain. The synthetized inertance is a complex frequency dependent function, which is predominantly real-valued in the frequency range between 5 and 1600 Hz. It is shown that it does not depend on the mechanical system properties, but only on the properties of the transducers used and the signal conditioning in the feedback loop. As a result, this frequency range can be adjusted according to a particular application.

Research on acoustic control of coupled vibration system of transducers using acoustic surface and topological defect structures

<sec>How to regulate the sound waves in the coupled vibration system of complex power ultrasonic transducers and design high-performance transducer systems has always been an urgent problem in the field of power ultrasound. Research has found that introducing various defects within the transducer system can improve the performance of the transducer coupled vibration system to a certain extent. However, the drawbacks of high loss, narrow frequency band, and sensitivity to structural parameters limit the further practical application of defect type phononic crystal transducer coupled vibration systems.</sec><sec>In order to improve the limitations of the coupled vibration system of defect-type phononic crystal transducers, effectively reduce energy loss, and enhance the efficiency of energy transmission, this paper introduces a topological defect structure with energy localization effect and a sound surface structure with high energy transmission efficiency into the coupled vibration system of the transducer. In this study, the acoustic surface structure and topological defect structure are used to excite defect states with energy localization effects and high energy transmission efficiency surface states, effectively regulating the vibration of the transducer coupled vibration system, and constructing a transducer coupled vibration system with high quality factor, low loss, and high energy transmission efficiency. By flexibly designing the geometric size parameters of the acoustic surface structure and defects, the vibration of the transducer coupled vibration system can be effectively controlled, thereby meeting the different functional requirements of the transducer coupled vibration system.</sec><sec>However, due to the excessive design parameters of surface structure and topological defect structure, the complexity of the design will be multiplied, greatly reducing the success rate of the design. Therefore, this study uses data analysis technology to establish a performance prediction model for the transducer coupled vibration system, in order to achieve the accurate prediction of system performance and change the shortcomings of low design efficiency and low success rate brought by traditional empirical trial and error methods.</sec><sec>In order to verify the effectiveness of the research, the coupled vibration system of the transducer is studied in simulation and experiment in this work. The simulation and experimental results indicate that the acoustic surface structure and topological defect structure can effectively regulate sound waves to improve the performance of the transducer coupled vibration system.</sec>

Terahertz detector based on Bi1-xSbx/Cu thermoelectric branches

Although most types of room-temperature THz detectors involving photothermoelectric (PTE) elements operate in a relatively narrow frequency band due to their antenna-coupled structure, such detectors may be implemented on the basis of non-resonant structures with broadband response due to broadband nature of PTE effect. This work is devoted to improvement of PTE detector sensitivity using serial connection of PTE elements consisting of bismuth-antimony thin films and Cu electrodes. The responsivity of this detector is studied at the frequency of 140 GHz. It is shown that the average voltage produced by PTE detector reaches up to 0.6 mV and is 15 times higher than one produced by continuous film consisting of the same material, while the maximum rate of voltage change is 17 times higher in comparison with continuous film response. Noise equivalent power (NEP) of PTE detector based on Bi1-xSbx/Cu branches is equal to 12.6 nWHz−0.5, and noise equivalent temperature difference (NETD) is equal to 4.9 m °C. This detector may be applied in the field of THz and microwave photonics in scanning security systems, THz signal detection in wireless communications, imaging and diagnostics in medicine, food industry and material characterization.

Quasi-BIC high-index resonators for liquid characterization and analysis

Capabilities to monitor the purity and mixture composition of liquids with the aid of low-cost portable devices can grant essential advantages in maintaining personal health safety. The overwhelming majority of consumer wireless devices operate at relatively small operational bandwidth, thus not allowing for retrieving material composition via dispersion characteristics. To mitigate the bandwidth limitations, resonant methods, granting precision in a small frequency window, might be of use. Here, we demonstrate a liquid sensor able to provide 90.5 kHz/RIU sensitivities owing to a resonator, supporting high-quality factor quasi-bound states in the continuum. The sensor's architecture encompasses a high-permittivity ceramic resonator and a capillary wrapped around it. The volumetric design increases the overlap between the electromagnetic mode and the liquid under test while maintaining resonant conditions within a relatively narrow frequency band. To demonstrate the capabilities of the proposed method, the UHF RFID band was considered, and temperature dependence of the distilled water permittivity was retrieved. Interfacing standalone low-cost electromagnetic sensors with widely available consumer-level wireless devices offers promising opportunities that contribute to the paradigm shift toward IoT.

High-efficiency broadband absorption/reflection integrated lossy acoustic metasurface via embedded microperforated wall

Period phase gradient metasurface plays a great role in promoting the innovation of acoustic application devices. However, harnessing the internal thermal viscosity of the period phase gradient metasurface to realize sound absorption and non-reciprocal transmission faces the narrow working frequency band and uncontrollable efficiency. In this paper, we propose a lossy metasurface by embedded microperforated walls to realize sound redirection and absorption with high efficiency than 90% simultaneously. The phase modulation is realized using an opening channel, which can cover the 2 π phase range in a broadband frequency range by changing the channel depth. The loss introduced by the microperforated walls can achieve efficient sound energy dissipation when negative reflection occurs. The functions can be switched between wave redirection and wave absorption by rotating the metasurface. In addition, this metasurface can redirect the incident wave below −10° and absorb the incident wave above 25° over a wide frequency range from 1500 to 6500 Hz. The simulation and experiment results of our design are in excellent agreement. This research provided a new bridge to integrate wave redirection and absorption with microperforated walls and may have potential applications in acoustic sensing, sound source identification, and mechanical fault diagnosis.

A lateralized alpha-band marker of the interference of exogenous attention over endogenous attention.

Scientists differentiate top-down from bottom-up visuospatial attention processes. While bottom-up attention is rapidly engaged by emerging demands from the environment, top-down attention in contrast reflects slow voluntary shifts of spatial attention. Several lines of research substantiate the idea that top-down and bottom-up attentional processes involve distinct functional systems. An increasing number of studies, however, argue that both attention systems share brain processing resources. The current study examines how salient visual events that engage bottom-up processes interfere with top-down attentional processes. Using neurophysiological recordings and multivariate pattern classification techniques, the authors show that these patterns of interference occur within the alpha-band of neural activity (8-12Hz), which implies that bottom-up and top-down attention processes share this narrow-band frequency brain resource. The results further demonstrate that patterns of alpha-band activity explains, in part, the interference between top-down and bottom-up attention at the behavioral level.

SSVEP-based visual acuity threshold estimation: linear extrapolation to noise level baseline with various noise definition criteria.

This study aimed to explore the effect of various noise definition criteria in linear extrapolation technique to noise level baseline on steady-state visual evoked potential (SSVEP)-based visual acuity assessment. Four noise definition criteria on frequency-domain, i.e., the mean amplitude at the two adjacent bins of the target frequency, the mean amplitude of a narrow frequency band on either side of the target frequency, the mean amplitude at a broad frequency band except for the target frequency and its harmonic frequencies, and the mean amplitude at a broad frequency band at resting state, corresponding to noise 1, noise 2, noise 3, and noise 4, were introduced to calculate noise level baselines. Then, two experiments were implemented. In experiment 1, electroencephalography (EEG) signals of resting state were recorded for fourteen subjects. In experiment 2, the visual stimuli of vertical sinusoidal gratings at six spatial frequency steps were used to induce SSVEPs for twelve subjects. Finally, SSVEP visual acuity was obtained via the SSVEP visual acuity threshold estimation of linear extrapolation technique to noise level baseline with various noise definition criteria. The bland-Altman analysis found that the difference between subjective Freiburg Visual Acuity and Contrast Test (FrACT) and objective SSVEP visual acuity was - 0.0892, - 0.1071, - 0.0745, and - 0.0804 logMAR and the 95% limit of agreement was 0.2150, 0.2146, 0.2046, and 0.2189 logMAR for noise 1, noise 2, noise 3, and noise 4, respectively, indicating that visual acuity of noise 3 definition criterion, i.e., the mean amplitude at a broad frequency band except for the target frequency and its harmonic frequencies, showed the best performance. This study recommended noise definition criterion 3 of the mean amplitude at a broad frequency band to calculate the noise level baseline in the linear extrapolation of SSVEP-based visual acuity assessment.

Overview of concept designs and results of the New Acoustic Insulation Meta-Material for Aerospace (NAIMMTA) project

Reducing aircraft cabin noise to improve the comfort of passengers is an important and challenging issue in aeronautics. Relatively uncomfortable high noise levels of around 80 to 90 dBA with strong low frequency range components (below 500 Hz) and a tonal character, predominantly related to the engine fan during take-off and approach, are deemed critical. The conventional acoustic materials seem to have reached their physical limits in terms of sound proofing, and therefore non-conventional solutions, such as metamaterials, are sought for their promising performance such as, a significant noise attenuation rate (dB/m), and the capability to be tuned at tonal or narrow band frequencies. An international collaborative project was created to develop novel technologies aiming at improving the existing noise control systems by obtaining an additional 5 dB noise reduction in the low frequency range (100 to 400 Hz) without deteriorating the thermal insulation. Moreover, the proposed solutions were expected to be tunable with respect to tonal noise (bandwidth of 5 Hz) or narrowband noise (bandwidth of 40 Hz). A major design and integration constraint imposed that the metamaterial had to be embedded in the current existing insulation blanket and add a maximum of 20% additional mass in comparison to the conventional insulation. This paper presents an overview of the various solutions developed from numerical simulations and novel manufacturing procedures development and optimization to performance characterization and validations.

Development of Compact Bandpass Filter Using Symmetrical Metamaterial Structures for GPS, ISM, Wi-MAX, and WLAN Applications

This article describes the development of a compact microstrip bandpass filter (BPF) for multiple wireless communication utilizations. The proposed bandpass filter consists of metamaterial unit cells that are symmetrical in shape. The design process involves the placement of four symmetrical split-ring resonators (SRRs) on the top plane of the BPF. It exhibits improved filter characteristics through the implementation of these SRRs. The filter was modeled and fabricated and its performance was evaluated using a Vector Network Analyzer. The designed bandpass filter shows a 5 GHz bandwidth covering the frequency band spanning from 1 to 5.2 GHz, with a quality factor value of 1.85 across 1.9 GHz, 3.3 across 3.3 GHz and 5.1 across 5.1 GHz. The metamaterial analysis was carried out using ANSYS ELECTRONIC DESKTOP. The proposed filter measures 20 × 18 × 1.6 mm3, which is significantly smaller than current filters. The designed bandpass filter occupies 50% of the space of a conventional filter. The designed bandpass filter exhibits a distributed surface current of 84 A/m, and 94 A/m across the wide- and narrow-band operating frequency. The simulated and measured results indicate that the suggested metamaterial filter is well-suited for multiband wireless applications like GPS (1.57 GHz), WLAN (2.4, 3.6, and 5.2 GHz), Wi-MAX (2.3, 2.5, and 3.5 GHz), and ISM (2.5 GHz).

Comparison of comprehensive quantitative EEG metrics between typically developing boys and girls in resting state eyes-open and eyes-closed conditions.

A majority of published studies comparing quantitative EEG (qEEG) in typically developing (TD) children and children with neurodevelopmental or psychiatric disorders have used a control group (e.g., TD children) that combines boys and girls. This suggests a widespread supposition that typically developing boys and girls have similar brain activity at all locations and frequencies, allowing the data from TD boys and girls to be aggregated in a single group. In this study, we have rigorously challenged this assumption by performing a comprehensive qEEG analysis on EEG recoding of TD boys (n = 84) and girls (n = 62), during resting state eyes-open and eyes-closed conditions (EEG recordings from Child Mind Institute's Healthy Brain Network (HBN) initiative). Our qEEG analysis was performed over narrow-band frequencies (e.g., separating low α from high α, etc.), included sex, age, and head size as covariates in the analysis, and encompassed computation of a wide range of qEEG metrics that included both absolute and relative spectral power levels, regional hemispheric asymmetry, and inter- and intra-hemispheric magnitude coherences as well as phase coherency among cortical regions. We have also introduced a novel compact yet comprehensive visual presentation of the results that allows comparison of the qEEG metrics of boys and girls for the entire EEG locations, pairs, and frequencies in a single graph. Our results show there are wide-spread EEG locations and frequencies where TD boys and girls exhibit differences in their absolute and relative spectral powers, hemispheric power asymmetry, and magnitude coherence and phase synchrony. These findings strongly support the necessity of including sex, age, and head size as covariates in the analysis of qEEG of children, and argue against combining data from boys and girls. Our analysis also supports the utility of narrow-band frequencies, e.g., dividing α, β, and γ band into finer sub-scales. The results of this study can serve as a comprehensive normative qEEG database for resting state studies in children containing both eyes open and eyes closed paradigms.

Rapid inverse design of high Q-factor terahertz filters [Invited

6 G communication technology using terahertz (THz) frequencies has increased the demand for components such as terahertz band filters. A high Q-factor filter capable of transmitting only narrowband frequencies, in particular, has gained significant research attention due to its wide range of applications. Here we obtained an optimal high Q-factor THz filter using an inverse design method that combines a double deep Q-learning model with an analytical solution within eight hours. Further, we confirmed the results of the inverse design using a numerical simulation, experimentally realized the high Q-factor THz filter, and discussed limitations of the spectral resolution of THz spectroscopy.

Critical-like Brain Dynamics in a Continuum from Second- to First-Order Phase Transition.

The classic brain criticality hypothesis postulates that the brain benefits from operating near a continuous second-order phase transition. Slow feedback regulation of neuronal activity could, however, lead to a discontinuous first-order transition and thereby bistable activity. Observations of bistability in awake brain activity have nonetheless remained scarce and its functional significance unclear. Moreover, there is no empirical evidence to support the hypothesis that the human brain could flexibly operate near either a first- or second-order phase transition despite such a continuum being common in models. Here, using computational modeling, we found bistable synchronization dynamics to emerge through elevated positive feedback and occur exclusively in a regimen of critical-like dynamics. We then assessed bistability in vivo with resting-state MEG in healthy adults (7 females, 11 males) and stereo-electroencephalography in epilepsy patients (28 females, 36 males). This analysis revealed that a large fraction of the neocortices exhibited varying degrees of bistability in neuronal oscillations from 3 to 200 Hz. In line with our modeling results, the neuronal bistability was positively correlated with classic assessment of brain criticality across narrow-band frequencies. Excessive bistability was predictive of epileptic pathophysiology in the patients, whereas moderate bistability was positively correlated with task performance in the healthy subjects. These empirical findings thus reveal the human brain as a one-of-a-kind complex system that exhibits critical-like dynamics in a continuum between continuous and discontinuous phase transitions.SIGNIFICANCE STATEMENT In the model, while synchrony per se was controlled by connectivity, increasing positive local feedback led to gradually emerging bistable synchrony with scale-free dynamics, suggesting a continuum between second- and first-order phase transitions in synchrony dynamics inside a critical-like regimen. In resting-state MEG and SEEG, bistability of ongoing neuronal oscillations was pervasive across brain areas and frequency bands and was observed only with concurring critical-like dynamics as the modeling predicted. As evidence for functional relevance, moderate bistability was positively correlated with executive functioning in the healthy subjects, and excessive bistability was associated with epileptic pathophysiology. These findings show that critical-like neuronal dynamics in vivo involves both continuous and discontinuous phase transitions in a frequency-, neuroanatomy-, and state-dependent manner.

Evidence of oceanic and atmospheric tides in underwater ambient noise time records

Multiyear time records of low-frequency ocean ambient noise show clear evidence of a modulating influence by major semi-diurnal and diurnal gravitational tides. These are displayed by means of a variance spectral analysis of noise time records obtained from the United Nations Comprehensive Nuclear Test Ban Treaty Organization for hydrophone stations at Wake Island, Ascension Island and Diego Garcia. Narrow-band noise frequencies ranged from ½ to 10 Hz. There is also evidence in the noise records of a diurnal atmospheric tide related to solar radiation and atmospheric loading. This same tidal presence is seen in wind speed records as well. Part of the challenge in the analysis is to distinguish between expected diurnal behavior in wind speed, with its accompanying effect on ambient noise, and the presence of actual tidal lines. A brief history of earlier observations of diurnal variation in underwater acoustics is presented, along with some suggestions of causal mechanisms.

Hybrid control of the radiated sound from a cylindrical shell with a voided soft coating

A hybrid passive-active control system composed of an array of inertial actuators is designed to attenuate sound radiation from a coated shell submerged in water. The coating embedded with cavities reduces the radiated sound from the shell over a broad frequency range. However, amplification in acoustic pressure occurs in narrow frequency bands associated with a spring-mass resonance of the coated shell as well as structural resonances. To address these resonances, we optimise the design of a hybrid passive-active control system composed of an array of inertial actuators tuned to different frequencies. Results show that the passive components of the inertial actuators can yield broadband reduction in the radiated sound at the shell circumferential resonances but are mostly ineffective at the spring-mass resonance. A hybrid control system in which the passive and active components are employed to target different resonances simultaneously is shown to effectively suppress the radiated sound from the coated shell.

Post-stall flow control on aerofoils by leading-edge flags

Self-excited oscillations of flags attached at the leading edge of aerofoils have been investigated at post-stall angles of attack at a chord Reynolds number of 100 000. Significant increases in the time-averaged lift coefficient and stall angle have been observed for three aerofoils: one symmetric, one cambered and one with a sharp leading edge. The aerodynamic improvement is due to the periodic formation of vortices caused by the flag oscillations. When the flag is near the aerofoil surface, it is lifted upwards by the induced velocity of the growing vortex. As the flag moves up, the vortex grows in strength and reaches maximum circulation when the flag is furthest from the aerofoil surface and subsequently sheds. Flags with large stiffness exhibit better spatial and temporal coherence of flag oscillations than the compliant flags, resulting in a larger maximum lift coefficient and higher stall angle. For all aerofoils tested, the best lift enhancement with respect to the clean aerofoils is found when the angle of attack is 6° to 10° above the stall angle of the clean aerofoil. High lift is observed when the flags are locked in with the wake instability in a narrow frequency band, depending on the flag mass ratio and length.

Validation of One Predominant Frequency Presence in Seismic Ground Displacement by Means of Deformation Response Spectra

There are very few results in the literature on spectral content of seismic ground displacement; nonetheless, these results are singular as most of the spectral content is limited to a very narrow low frequency band, contrary to ground acceleration. These few spectral characterizations have been obtained, expectedly, by means of power spectral or Fourier analyses of ground displacement records, only. As these records are not as reliable as ground acceleration records, the existence of a clear predominant frequency in ground displacement warrants confirmation through a different procedure. We propose a corroboration method of this highly narrow-band characteristic that is based on the more dependable acceleration signal, rather than on the same ground displacement record that is the subject of study. Specifically, displacement response spectra are analyzed (which rely on acceleration records) to verify previously observed neat predominant frequencies in ground displacement, which is a novelty.

Damping contribution of viscoelastic core on airborne sound insulation performance of finite constrained layer damping panels at low and middle frequencies

The airborne sound insulation performance of finite sandwich panels is often significantly worsened by resonant transmission components in low and middle frequencies. In this paper, damping contribution of viscoelastic core on sound transmission loss (STL) of finite constrained layer damping (CLD) panels is studied in narrow frequency bands. A fully coupled layer-wise approach is used with a generalized high-order shear deformation hypothesis that accounts for all types of deformations in the core. The influence of several parameters is investigated extensively. Results show that the adverse impact of the first-three odd-odd order modes, namely (1,1), (3,1), and (1,3) modes, as well as some higher-order modes on STL cannot be disregarded. The constrained viscoelastic core plays a crucial role in enhancing, or even eliminating, dips of STL spectrum at resonant frequencies. Additionally, it can considerably counterbalance a relatively broadband reduction of STL caused by the inter-modal coupling in middle frequencies. The damping mechanism can be divided into two aspects: (i) the reduction of modal amplitude by vibration energy dissipation, and (ii) the change of bending modal shapes. CLD treatment is a concise and effective way to achieve stable sound insulation performance.