The quantitative analysis of the effect of low-frequency vibrations on the sitting comfort has been a pivotal focus in the field of transportation engineering. In this study, the transmission of vibration through the human-seat system with different excitation conditions is predicted and analyzed using the finite element modeling. Individual finite element models for the human body and the seat, along with their respective contact properties, are constructed and integrated into an overall finite element model of the human-seat system. The model parameters are validated utilizing experimental data from static body pressure distribution at cushion and backrest locations, as well as the measured seat transmissibility obtained with the vertical excitation. The results indicate the finite element model, validated through the calibration, demonstrates a good fit with experimental data for the seat transmissibility under the fore-and-aft excitation. However, there is a deviation in the amplitude at the resonance frequency. Additionally, the model predicts that the resonance frequency of the seat transmissibility decreases with an increase in the excitation amplitude, and this trend aligns well with experimental results, particularly under the vertical excitation. The constructed model accurately reflects the dynamic response of the human-seat system with different conditions. It serves as a valuable reference for the seat design.

The command‑FxLMS algorithm for multi‑order noise modulation has unnecessarily high output gain when there is a phase error between the command signal and the disturbance signal. Aiming at this problem, a multi‑order active sound profiling system based on the modified differential phase scheduled command filtered‑x least mean square (DPSC‑FxLMS) algorithm is constructed. By adjusting the phase of the command signal to keep it in phase with the disturbance signal, the output level of the control signal is reduced while keeping the same control performance. Simulation analysis and comparison of engine steady‑state multi‑order noise modulation using the above algorithms are carried out, and the control effect of the algorithms is verified. For the in‑phase case, two algorithms share the identical performance and control effect, while for the out‑of‑phase case, the DPSC‑FxLMS algorithm requires less control effort than the command‑FxLMS to achieve the same control performance. The multi‑order noise modulation simulation of the above algorithm is carried out using the multi‑order noise signal collected from a real vehicle. The simulation results validate the feasibility of the proposed algorithm for practical in‑vehicle applications.

A method of product sound quality classification and limit value evaluation based on satisfaction is proposed for the quantitative evaluation of product noise level by product manufacturers, product quality evaluation institutions, consumers and other stakeholders. Through subjective evaluation experiment and questionnaire survey, the relationship between product noise quality index and satisfaction degree was obtained. After comprehensive consideration of the current production level of the industry, affordability and consumer interests and other factors, the sound quality classification and limit assessment were carried out. The method is applied to household appliances and ships, and the product noise quality classification and limit evaluation are carried out to verify the effectiveness and applicability of the proposed method. The characteristics and problems needing attention when the method is applied to different fields and scenarios are discussed.

As a component widely used in various industries, the noise problem of fans has always attracted people’s attention. In equipment with relatively low noise energy levels, abnormal noise, such as whistling, or rattlesing, from fans are key factors that lead to user complaints. Taking laptop fans with various abnormal noises as an example, the correlation between the severity of fan abnormal noise and the main psychoacoustic parameters of sound quality was studied, and a linear regression model between the subjective score of abnormal noise and the objective parameters was established. The results show that loudness, sharpness, prominence ratio, and the frequency corresponding to the maximum value of pitch affect the subjective feeling of abnormal noise. The multivariate linear model including loudness and sharpness can better evaluate the subjective score of the severity of abnormal sound.

To ameliorate the low-frequency sound absorption performance of bulk porous materials, a theoretical model for predicting the sound absorption of the composite structure incorporating flexible ultra-thin and bulk porous materials is derived. The model integrates Johnson-Champoux-Allard (JCA) model and acoustic impedance model for flexible ultra-thin materials, employing non-woven fabric and melamine cotton as illustrative instances. The accuracy of this model is validated through experimental verification, and particle swarm optimization (PSO) is employed to optimize the parameters of the composite structure. The analysis results indicate that the addition of a layer of non-woven fabric on the surface of traditional bulk porous materials significantly enhances the low-frequency sound absorption performance. This paper provides a theoretical foundation for the determination, analysis and optimization of the sound absorption performance of the composite sound-absorbing structure composed of flexible ultra-thin and bulk porous materials, Additionally, it presents an effective method for improving the low frequency sound absorption performance without changing the thickness of the original sound absorber.

In order to explore the correlation between seated body pressure distribution and biomechanical loading, a setup scheme for the human-chair contact surface for human biomechanical modelling is proposed using body pressure information as a guide. The contact between the human body and the seat is simulated by a certain number of contact points, and based on the experimental body pressure distribution data, the relative contact strength is set as the relative magnitude of the average pressure in each partition of the body pressure cloud map. Through comparison, it is discovered that the average contact strength is set between 200~600, which can improve the solution accuracy and take into account the real muscle activation effect. At the same time, the scheme of different numbers of contact points was discussed, and it is more reasonable to choose to set 8 contact points in a comprehensive view. After comparing with the experimental data in the literature, it is shown that the contact scheme based on the body pressure distribution of the human chair biomechanical model can accurately reflect the muscle activation, joint force and other biomechanical indicators. Muscle activation and joint forces under hardwood planks and foam cushions were compared based on a contact scenario setup, explaining the reasons for more comfortable foam seating from a biomechanical point of view.

Artificial neural network modelling has been preliminarily employed to investigate effects on the biodynamic responses. In order to evaluate the vibration transmission characteristics of the seat‑occupant system, further quantitative research is needed. Drawing from a low frequency experimental investigation into whole body vibration, this study is aimed to develop an ANN model with the response surface method optimization. The age, stature, sitting height, knee height, buttock‑to‑knee, weight, gender, BMI, cushion thickness and frequency are used as network input to explore that these how to predict transmissibility from the seat base to the seat pan. Based on the interaction between hyperparameters, the mapping relationship between model hyperparameters and prediction performance indexes was established, and the optimal combination of hyperparameters was optimized and obtained. The results show that the resonance frequencies in the vertical inline and the fore‑and‑aft cross‑axis transmissibilities from seat base to seat pan decreased with increasing thickness of foam at the seat pan. BP‑ANN model has good performance in establishing the nonlinear relationship between the anthropometric, seat structure characteristics and vibration transmission characteristics of seat‑occupant system. Compared with BP‑ANN model, the error of RSM‑BP‑ANN model is reduced by 25% and 18% respectively in predicting vertical in‑line transmissibility and fore‑and‑aft cross‑axis transmissibility from seat base to seat pan. And this also provides an idea for adjusting the parameters of neural network models to improve the prediction accuracy of seat transmissibility.

The human body’s perception of one stimulus may change due to the occurrence of another stimulus, which leads to the possibility of a masking effect between vibrations that successively act on the human body. Whether the masking effect is significant or not is related to many factors. This study designed and carried out a seated human vibration experiment to explore the impact of time-domain masking effects on vibration comfort of the seated human body. Designed variables include： intensity of masking signals (3 levels）, vibration interval (4 levels）, and masking sequence (forward and backward）. The experimental results show that these factors do have an impact on the overall comfort when subjected to whole-body vibration； comparing the effects of forward masking tests and backward masking tests, the discomfort caused by backward masking tests is stronger； with the increase of vibration time interval and the decrease of the masking signal strength, the influence of the masking effect on human body discomfort gradually weakens. It can be found that in addition to frequency domain weighting, the time domain characteristics of vibration amplitude also have a non-negligible impact on the evaluation of human vibration discomfort. Comfort prediction based on objective responses should consider the influence of more factors.

Ride comfort evaluation of high‑speed trains has vital importance for continuously improving the structural design and passengers’ ride satisfaction. This paper tries to evaluate the long‑term and momentary ride comfort of high‑speed trains in China in the light of the European standard EN 12299：2009, and discuss the applicability of the standard. Objective vibration test and subjective comfort evaluation were carried out in a comprehensive inspection train. Average comfort index and discrete events comfort index recommended by the EN 12299：2009 standard were briefly introduced, and the two indexes were selected for long‑term comfort evaluation and momentary comfort evaluation respectively. For the three kinds of track sections with different subjective feelings, based on the measured vibration acceleration data, the long‑time and momentary comfort evaluation indexes were calculated respectively, the comfort of high‑speed train and track quality were analyzed. Combined with the subjective evaluation results, the applicability of the corresponding indexes was analyzed, and attempts were made to put forward suggestions for improvement. according to which the comfort of high‑speed rail ride and the quality of the track into the standard is analyzed. The applicability of these indices was analyzed by referring to the subjective evaluation, and certain suggestion was proposed to modify the indexes.

Vibration limit is one of the most essential contents in vibration serviceability research. Former studies showed that many factors, such as biological and environmental factors, significantly affected vibration limits deeply. As a reason of defects in traditional research, such as small scale data and unreal test environment, quantitative relationships between vibration limits and these factors stayed unknown. Based on data collected by crowd sensing in real environment, crest factor of vibration/ BMI/ human age/ floor of building were found key factors by using maximal information coefficient (MIC) in coefficient analysis. Functional relationship and 95% confidence intervals between vibration limits and key factors were proposed, respectively. Lilliefors test and normal probability plot show that residuals between fitted values of limits and measured ones follow a normal distribution. A novel approach of estimating vibration serviceability based on probability is proposed when key factors and vibration magnitude are known.