Vibration Noise Research Articles

Minimal model identification of drum brake squeal via SINDy

The industrial standard in the design and development process of NVH(Noise Vibration Harshness) characteristic of brakes is the application of Finite Element(FE) models with a high number of degrees of freedom in the range of one or several millions. Nevertheless, parallel experimental investigations are still indispensable. On the other hand, minimal models with, due to the inclusion of the self-excitation process, at least two degrees of freedom are well known to be capable to explain qualitatively phenomena as instability of the desired non-vibrating solution or limit cycle oscillation but are in general very inaccurate in predicting the dynamics of a specific real brake. This is because the underlying physical assumptions are already too restrictive and model parameters (especially those referring to nonlinearities) are widely unknown. To overcome this problem, the data-driven modeling approach SINDy(Sparse Identification of Nonlinear Dynamics) is applied to identify appropriate nonlinear functions for a brake squeal minimal model. A problem thereby is the limited database. It turns out that the naive implementation of the method yielding the lowest possible residuum does not necessarily provide physically meaningful models and results, respectively. Instead, a constrained model that incorporates physical knowledge is used to robustly identify parameters and reproduce realistic dynamic behavior. Thereby, several appropriate models with coexisting limit cycles and stationary equilibrium are identified. In particular, it was found that the angular position of the brake drum has a significant influence on the model parameters and therefore must be taken into account in a model with long-term validity.

Commuter Experience: An Assessment of Metro-Train Comfort Amidst Operational Vibroacoustic Conditions

This study investigates the impact of different passenger rolling stock structures and train configurations on vibrations and noise generated during operation. Vibroacoustic measurements were performed during acceleration, constant speed, and braking phases to analyze the effects using statistical analysis according to the relevant standards, revealing a statistically significant relationship between the equivalent noise level and vibration dose. In the context of the expanding Warsaw metro network, which is adding new lines and modern rolling stock, trends in the development of metro rolling stock were analyzed using five different types of metro vehicles, from the oldest to the newest designs. Vehicle performance was ranked in the context of ride comfort using standards and combined vibration and noise measures. The research results allowed for a collective comparative assessment of the construction of individual types of passenger rolling stock in terms of vibroacoustic phenomena, thanks to which it is possible to assess the impact of modern solutions and the justification for investing in modern rolling stock. Newer trains generally record significantly lower vibration and noise levels. The difference between the oldest and the most modern vehicle types is 57% for the vibration acceleration level (0.08 ms−2 RMS) and 66% for the noise level (2.2 dB LAeq).

Multilayer ceramic capacitor induced audible noise simulation

Multilayer ceramic capacitors (MLCCs) are one of the most widely used capacitors. Their small size, high capacitance, high reliability and low cost make them ideal for miniaturized electronic devices. However, their piezoelectric effect may cause the deformation of the capacitor associated with the applied voltage. Even worse, the deformation may cause the PCB vibration and potential noise radiation, which can be a problem for devices designed to be quiet, such as cellphones, earbuds, laptops, etc. This paper introduces how MLCCs can cause PCB vibration and noise radiation problems by simulating a single MLCC with piezoelectric effect. And then, a methodology is proposed on how to quantify the MLCC as vibration load source. Moreover, a simplified process is illustrated to simulate the MLCC induced noise radiated from circuit boards. Finally, a couple applications are demonstrated by using the developed process.

Extremely low-vibration experiments with resolutions nanometer range supported on air tables may also require a low-noise environment

The paper reports key results from an extensive diagnostic study examining a room's vibration and acoustic noise environments and their correlation to measurement noise. Vibrations of unknown origin were contaminating research being performed on highly vibration-sensitive apparatus in the basement of a recently completed engineering building. The research involved extensive single‐molecule microscopy requiring resolutions down to 1 nm carried out on an optical table supported on pneumatic legs. Researchers reported that the experimental noise was reported to be of random amplitude less than 40 nm. The problem did not appear to correlate with obvious building or personnel activities. The design vibration and noise criteria for the new space had been VC-E and NC-40, respectively. At the time of the study, the ambient floor vibrations were several classes better; however, the acoustic environment was slightly worse. FRF correlation was calculated between combinations of the tabletop and floor vibrations and airborne sound. The best correlation was between tabletop vibration and airborne sound. The supply air was a significant part of the problem, but the ceiling offered very little attenuation from above. Some of the sound was being generated above the ceiling by HVAC components other than the supply air.

Comparison of train noise and vibration measurements with U.S. Department of Transportation model predictions

Wayside noise and ground-borne vibration measurements of freight and light rail train operations were carried out in Denver, CO in support of the Burnham Yard Transportation Planning Study being pursued by the Colorado Department of Transportation (CDOT). This study was intended to evaluate various track layout alternatives for the Consolidated Main Line (CML) freight railroad alignment and enhancement of Regional Transportation District (RTD) light rail operations while maintaining options for Front Range Passenger Rail (FRPR) within Burnham Yard and the surrounding areas. The objective of the measurements was to compare measured train noise and vibration levels with predictions using models sanctioned by the U.S. Department of Transportation (USDOT) in order to validate the use of these models to assess the noise and vibration impacts of the project alternatives. The models included the Federal Railroad Administration (FRA) Chicago Rail Efficiency And Transportation Efficiency (CREATE) freight noise model, the FRA Horn Noise Model, and the models included in the Federal Transit Administration (FTA) Transit Noise and Vibration Impact Assessment Manual. Based on a comparison of measured and modeled results, it was concluded that the USDOT models could be used to assess noise and vibration from train operations in the Burnham Yard Study Area.

Noise exposure assessment of over-track buildings induced by train operations

The noise generated by trains running beneath these buildings significantly impacts residents and has garnered growing attention. To evaluate the influence of trains running under buildings on internal noise levels, this study conducted subjective questionnaire surveys and field measurements for noise and vibrations in two buildings located in Wuhan and Shenzhen, China. The subjective annoyance of noise was investigated through a survey conducted with a total of 152 participants. The measurement points were positioned at the 2nd-floor level in close proximity to the building’s support structures, as well as on the various floors. The contribution of airborne noise and structure-borne noise to the acoustic environment was identified, elucidating their respective impacts on the overall soundscape. Furthermore, an investigation was conducted to examine the correlation between structure-borne noise and floor vibrations, which was then compared with the guidelines provided by FTA (Federal Transit Administration). The results found that the indoor noise within the over-track building, resulting from train operations, mainly stems from structure-borne noise characterized by a frequency-dependent correlation among floor vibrations. This phenomenon is predominantly observed below 200 Hz with prominent peaks specifically at 40 Hz. The utilization of the FTA (Federal Transit Administration) recommended formula for predicting structure-borne noise levels based on velocity levels may result in an underestimation of the noise impact, particularly with regard to noise energy above 100 Hz. These findings hold significant implications for the design and construction of similar over-track buildings.

An equivalent and simplified approach for acoustic noise prediction in a PM synchronous motor based on the semi‐analytical‐FEM model

AbstractThe vibration and acoustic noise of a permanent‐magnet synchronous motor are analysed and evaluated. Acoustic noise sound levels, their prominent frequencies, and the noisiest motor speed range are predicted. According to many resources, the radial vibration of the stator system due to the magnetic attraction between rotor permanent magnets and stator iron teeth is the main reason for the acoustic noise propagation of the PMSMs. The dominant orders of the spatial circumferential harmonics of the radial magnetic forces (RMFs) have been investigated and compared. The complete and complicated mechanical components, materials, and harmonics of the magnetic forces of the motor and their interaction are simplified and equalised to a vibration model, which consists of the interaction between the stator system and the dominant harmonic orders of the RMFs. Based on this approach, the simplest and most adequate semi‐analytical‐FEM model for noise prediction in PMSMs is proposed. This model, in addition to simplification, clarifies the role of the main mechanical and electromagnetic origins of noise generation. The acoustic noise prediction, using the proposed method has been compared with the experimental results. There is a proper agreement between the analytical, the FEM, and measurement results.

Research on the effects of volute area ratios on centrifugal pump internal flow and noise

Centrifugal pumps, which are essential for the transfer of fluids, are extensively utilized in industries like aerospace and new energy vehicles. These fields require pumps to meet rigorous standards in terms of reliability, efficiency, and vibrational noise while also imposing stringent restrictions on their size and weight. Therefore, achieving optimal performance in terms of both efficiency and noise reduction for centrifugal pumps in limited space poses a considerable difficulty. This study investigates the impact of different volute area ratios on the internal flow properties and noise levels of centrifugal pumps, using area ratio theory as a foundation. Both experimental and computational simulations are used, with the pump dimensions kept constant. The results demonstrate that an augmentation in the volute area ratio greatly improves the pump's exterior properties, notably decreases internal vorticity, and boosts flow conditions. The pressure fluctuations in the pumps show an overall decrease, accompanied by changes in their distribution patterns. In addition, the sound pressure levels in the exterior sound field of the pumps typically decrease, accompanied by obvious changes in directivity. The sound pressure levels within the internal sound field are significantly reduced, especially in areas of the volute wall that were previously known for having high sound pressure. By analyzing the relationship between sound pressure and pressure pulsation on the wall surface of the volute, as well as the impact of area ratio on pressure pulsation distribution in the sound field of the centrifugal pump, it is evident that the theory of area ratio can be utilized to effectively decrease pressure pulsation in the centrifugal pump, thereby reducing the noise generated by the pump.

On the influence of porous coating on vibration response and noise reduction of cylinders at high Reynolds numbers

On the influence of porous coating on vibration response and noise reduction of cylinders at high Reynolds numbers

Dynamical behavior of fluid–structure interaction in ducts with rigid and flexible interfaces: Modeling and analysis

This study investigates the propagation of fluid–structure coupled waves in a duct featuring both rigid and flexible interfaces. Two cases are considered: in the first case, with a rigid interface, the truncated form of solution preserves the conservation law, while in the second setting, the power balance is not preserved initially, but is rectified as the number of modes, denoted as N, approaches infinity. The discrepancy is explained by specific equations and the presence of delta functions to enforce edge conditions on the membrane at the interface. The Galerkin approach is adopted to address this issue, expressing the membrane’s displacement using a generalized Fourier series. The investigation establishes a framework for modeling higher-order boundary conditions within a duct, employing the mode-matching (MM) method. The study also delves into the scattering components of power, which vary significantly for the two cases. These findings have implications for noise control devices, particularly in active noise control measures utilizing flexible components to dampen both noise and structural vibrations.

Separation of tire tread vibration noise and air pumping noise using frequency band noise data

Separation of tire tread vibration noise and air pumping noise using frequency band noise data

An optimal sensor layout method based on noise reduction estimation for active road noise control

Active noise control (ANC) is an effective method to suppress vehicle road noise. The rapid selection of the reference sensor set and rational selection of its layout position are crucial for determining the vibration noise transmission paths with high contributions, which determines the noise reduction performance of the active road noise control (ARNC) system. The reference sensor set selected by the conventional multiple coherence function (MCOH) method does not always ensure the optimal noise reduction performance and the matrix singularity problem based on the Fisher information matrix (FIM) expansion method. To alleviate this problem, this paper proposes a method based on the overall level of noise reduction (OANR) and the FIM to select a set of reference sensors and determine their positions. This method uses an optimal causally constrained Wiener filter to estimate the theoretical OANR for each control area to ensure the reference sensor selected has the optimal noise reduction performance, and it expands efficiently based on the FIM method to select a set of reference sensors. Besides, the matrix singularity problems in the FIM-based expansion method are solved using noise frequency summation and matrix operation, which makes the method more universally applicable. Numerical simulations are performed to analyze and evaluate the noise reduction performance and selection efficiency of the proposed method under different conditions. In addition, a series of real vehicle ANC experiments are conducted. The results show that the reference sensor set selected based on the proposed method has an obvious advantage in noise reduction performance, and only four reference sensors are needed to achieve 4.63 dB(A) noise reduction in ARNC experiments. It fully confirms the effectiveness of the proposed method in real vehicle applications.

Bayesian time domain approach for damping identification and uncertainty quantification in stay cables using free vibration response

The dynamic characteristics, particularly damping, play crucial roles in the design, monitoring, and vibration control of stay cables. The free vibration test, commonly used for damping identification of stay cables, demonstrates notable technical advantages in specific mode excitation and improving the signal-to-noise ratio. Nevertheless, challenges arise from uncertainties associated with ineluctable ambient vibration influences and noise contamination in measured responses. In recent years, there has been a growing interest in Bayesian modal identification methods due to their remarkable ability to quantify uncertainties. However, further advancements are needed in the time domain, particularly when addressing the relatively short duration of free vibration response data. This is essential to minimize the impact of background ambient vibration and enhance the accuracy of modal identification. This paper proposes a novel Bayesian modal identification approach specifically crafted to address free vibration data affected by ambient vibrations, aiming to achieve high-precision modal identification and effective uncertainty quantification from free vibration response of stay cables. Additionally, a speedup algorithm is used for determining the most probable values (MPVs) to enhance computational efficiency. The efficacy of the proposed approach is validated through simulated scenarios, encompassing both a single-degree-of-freedom structure and a finite element model of a stay cable. Furthermore, the effectiveness of the proposed method is validated through its application in a laboratory test involving a scale model of the stay cable, as well as in a field test of actual stay cables of Sutong Bridge. The results demonstrate that the proposed method achieves high accuracy in identifying modal damping ratios, and effectively quantifies uncertainties in the identification results.

Optimal Time Frequency Fusion Symmetric Dot Pattern Bearing Fault Feature Enhancement and Diagnosis.

Regarding the difficulty of extracting the acquired fault signal features of bearings from a strong background noise vibration signal, coupled with the fact that one-dimensional (1D) signals provide limited fault information, an optimal time frequency fusion symmetric dot pattern (SDP) bearing fault feature enhancement and diagnosis method is proposed. Firstly, the vibration signals are transformed into two-dimensional (2D) features by the time frequency fusion algorithm SDP, which can multi-scale analyze the fluctuations of signals at minor scales, as well as enhance bearing fault features. Secondly, the bat algorithm is employed to optimize the SDP parameters adaptively. It can effectively improve the distinctions between various types of faults. Finally, the fault diagnosis model can be constructed by a deep convolutional neural network (DCNN). To validate the effectiveness of the proposed method, Case Western Reserve University's (CWRU) bearing fault dataset and bearing fault dataset laboratory experimental platform were used. The experimental results illustrate that the fault diagnosis accuracy of the proposed method is 100%, which proves the feasibility and effectiveness of the proposed method. By comparing with other 2D transformer methods, the experimental results illustrate that the proposed method achieves the highest accuracy in bearing fault diagnosis. It validated the superiority of the proposed methodology.

Three-dimensional phononic crystals with self-similar structures

Acoustic metamaterials have the advantages of designability, strong pertinency, small size and good effect, and have good application value in solving the problem of sound insulation and noise reduction. Phononic crystals with wide bandgap and multi-bandgap can inhibit elastic wave propagation to some extent. In this study, a three-dimensional phononic crystal model with self-similar properties is designed by using fractal method. First, an initial unit is constructed, then the arm of the initial unit is replaced with the structure itself to form a self-similar structure. The self-similar model can block sound waves in the wide band and multi-band range. By changing the structure shape and size of phononic crystal, the sound wave blocking in different frequency range is also studied. At the same time of continuous optimization of the structure, the variation rules of the model band structure under different parameters are summarized. To find the good parameters of broadband and multi-band sound wave blocking, so as to achieve the effect of vibration isolation and noise reduction. The finite element method is used to simulate the vibration of the model to verify the existence of elastic wave bandgap. Phononic crystals have a good prospect in the field of sound insulation and noise reduction.

Comprehensive analysis of band gap modulation of hexagonal fan blade and optimized ligament structure in the low-frequency range

This paper proposed a meta material model with low-frequency wide band gap and band gap tunability, optimized its structure as a multibranch chain structure, and analyzed the band gap relationship of above two models based on Brag's theorem and finite element method. Among them, the fan base structure has a band gap of 65.92 % within 20,000 Hz, and the band gap is optimized to low-frequency after the structure is optimized, and the band gap reaches 75.94 % within 10,000 Hz. The effects of the ligament width and the thickness of the center parcel layer on the band gap distribution of the structure are also discussed, and the wave transmission characteristics in the structure are explored by group and phase velocities to verify the acoustic performance of the structure. The results show that the smaller the ligament thickness is, the lower the first band gap opening frequency of the structure is; when the thickness of the central wrapping layer is increased, the structure develops the band gap at the center frequency of 3000 Hz to a lower frequency and generates an ultra-wide band gap at the center frequency of 6000 Hz. These findings can provide a new idea for low-frequency vibration isolation and noise reduction.

Ageing tests with high temperatures of prototype vibroacoustic isolators – under ballast mats (UBMs) based on recycled materials

This study focuses on experimental ageing tests with high temperatures carried out on prototype under ballast mats (UBMs) according to the procedure of the European standard EN 17282, which was introduced in late 2020. Most of the analysed UBM samples are based on recycled elastomeric materials, such as styrene-butadiene rubber (SBR) granules and fibres from end-of-life car tyres and rebond polyurethane waste from polyurethane product manufacturing plants. Additionally, two variations of the mat based on mineral wool are analysed. Significant differences in the values of static and dynamic characteristics measured before and after the ageing tests are demonstrated, and permanent deformations of the recycled polyurethane-based mats are shown. Moreover, it is proved that the elastomeric mats based on recycled rubber materials (SBR granules and fibres) have high durability and are an effective solution in terms of protection against vibration and structure-borne noise from railway traffic. In addition, the authors propose criteria for assessing the results of the ageing test with high temperatures of UBMs tested according to the procedure of EN 17282.

A dragonfly-wings like self-powered magnetic field sensor with vibration noise restriction function

As the rapid development of the Internet of Things (IoT), the demand for the self-powered sensors and devices has become urgent. In this work, we present a self-powered magnetic field sensor based on a biomimetic dragonfly-wings like magnetoelectric (DWL-ME) laminated cantilever. The two pairs of wings in DWL-ME cantilever operating in anti-phase vibration modal has shown a strong magnetoelectric coupling for converting magnetic field energy into electric energy with an energy harvesting density of as high as 100 µWOe−2cm−3. It also shows a linear response to an alternating magnetic field (HAC) with a high detectability of 2.7 nT at 60 Hz. Compared to traditional cantilever beam ME sensors, its vibration noise is also effectively decreased by more than 30 dB due to the anti-phase vibration modal of two pairs of wings. The proposed biomimetic design strategy has inspirational significance for future sustainable, self-powered intelligent sensor networks.

Electromagnetic noise characteristics analysis and noise traceability in induction motor

Abstract To investigate the electromagnetic vibration and noise issues in induction motors, this study employs a combined methodology of experimental, theoretical, and simulation approaches to analyze the characteristics of electromagnetic noise. Initially, a theoretical analysis of the radial electromagnetic force of the motor is conducted, followed by a simulation of the motor’s electromagnetic vibration and noise at a working condition of 3000 rpm, incorporating a Multiphysics coupled analysis of electromagnetic-vibration-noise. Vibration testing on a specific compressor motor reveals that the primary vibration noise characteristic frequency is centered around 2000 Hz. A comparison between simulation and experimental results shows a high degree of congruence, indicating the reliability of the simulation method. Subsequently, an acoustic camera kit, Brüel & Kjær PULSE Reflex, based on a beamforming method, is employed for noise source identification and acoustic holography testing at 3000 rpm, which successfully localizes the noise sources. The analysis and experiments provided herein can serve as a reference for the development of electromagnetic vibration noise suppression techniques in induction motors.

Preparation and performance study of polyurethane/ kaolinite nanocomposite insulation materials

Abstract Polyurethane foam insulation materials exhibit excellent noise reduction, shock absorption and vibration damping capabilities while being cost-effective and easily moldable. They have found widespread applications in diverse fields such as automotive, machinery, packaging, insulation, healthcare and construction. However, the application range of this traditional organic material is limited by issues related to thermal stability and flame retardancy. By achieving uniform dispersion of nanoparticles, composite materials exhibit enhanced comprehensive properties in terms of flame retardancy, oxidation resistance, physicochemical stability and structural performance. Polyurethane/Kaolinite nanocomposite insulation materials were prepared by using the in situ intercalation compounding method. X-ray diffractometer, Fourier infrared spectrophotometer, thermogravimetric analyzer and scanning electron microscope were used to characterize the thermal stability of the composite material obtained under different preparation conditions and the state of the nanomaterial in the system. The results showed that the composite material with good dispersion of kaolinite in the matrix was obtained by effective surface modification through dimethyl sulfoxide. The doping of low-concentration kaolinite can improve the thermal stability of polyurethane. When the mass fraction of nano-kaolinite is 5%, the initial decomposition temperature of the composite system is 47°C higher than that of pure polyurethane and the system achieves the highest thermal stability.