Applied Sciences

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13 pages, 4561 KiB

Open AccessArticle

Noise and Vibration Analysis of Electric Oil Pump with Asymmetric Pitch Control for Gearbox in Hybrid and Battery Electric Vehicle

by Chinchul Choi

Appl. Sci. 2025, 15(10), 5779; https://doi.org/10.3390/app15105779 - 21 May 2025

Viewed by 164

Abstract

This study proposes an asymmetric pitch control technique for electric oil pumps with symmetric gear-type pumps in order to reduce noise and vibration. For vane pump noise reduction, mechanical asymmetric pitch arrangements of each vane are widely used. However, the mechanical asymmetric pitch [...] Read more.

This study proposes an asymmetric pitch control technique for electric oil pumps with symmetric gear-type pumps in order to reduce noise and vibration. For vane pump noise reduction, mechanical asymmetric pitch arrangements of each vane are widely used. However, the mechanical asymmetric pitch arrangement approach is not applicable in gear-type pumps due to structural limitations. The proposed asymmetric pitch control method provides similar effects to the mechanical asymmetric pitch arrangement by employing instantaneous motor torque controls for an electric oil pump with a gear-type pump. The magnitude of motor torque for each pump tooth is determined with an asymmetric pitch formula, which has been widely used for mechanical vane pumps in previous studies and patents. A formula for the shape of instantaneous motor torque is proposed for the analysis of pressure fluctuations of pumps, which is a combination of trigonometric and exponential functions. The calibration factors for the magnitude and shape can be adjusted according to the characteristics of a given pump. The experimental results for a 400 W electric pump show that the proposed method reduced and dispersed the noise peak by approximately 4 dB(A) in comparison with the normal control, and affected hydraulic performance with a less than 1% decrease in flow rate in not only pump-level but also gearbox-level test environments. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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12 pages, 2671 KiB

Open AccessArticle

Testing the Frequency Response Control Function of Level-Dependent Earplugs

by Emil Kozlowski, Rafal Mlynski and Krzysztof Lada

Appl. Sci. 2025, 15(10), 5741; https://doi.org/10.3390/app15105741 - 21 May 2025

Viewed by 109

Abstract

Noise and the use of hearing protectors can impair the perception of useful sound at work. One solution to this problem is the use of hearing protectors with electronic systems. The aim of this article was to present the results of tests that [...] Read more.

Noise and the use of hearing protectors can impair the perception of useful sound at work. One solution to this problem is the use of hearing protectors with electronic systems. The aim of this article was to present the results of tests that verified the ability of the filters implemented in earplugs to control the frequency response. Tests were conducted to verify the implementation of digital filters in the sound processor. The filtration method proposed in octave bands with center frequencies of 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz was fully sufficient. A high degree of compliance of the characteristics of the implemented solution with the standardized characteristics was observed. Measurements using an acoustic signal also confirmed the filters were correctly implemented in the designed earplugs. The filters attenuated the sound to about 30–40 dB. The obtained results allowed us to conclude that the developed earplugs can be used in the future to protect employees against noise, and, at the same time, effectively deliver useful signals to their user. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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13 pages, 3647 KiB

Open AccessArticle

A New Signal Processing Method for Time-of-Flight and Center Frequency Estimation

by Olgirdas Tumšys

Appl. Sci. 2025, 15(10), 5721; https://doi.org/10.3390/app15105721 - 20 May 2025

Viewed by 161

Abstract

Ultrasonic signal processing methodologies use many signal parameters to be investigated, one of which is time-of-flight (ToF). There are many and various methods used to determine ToF, such as threshold detection, peak-based methods, cross-correlation, zero-crossing tracking algorithms, etc. The application of most of [...] Read more.

Ultrasonic signal processing methodologies use many signal parameters to be investigated, one of which is time-of-flight (ToF). There are many and various methods used to determine ToF, such as threshold detection, peak-based methods, cross-correlation, zero-crossing tracking algorithms, etc. The application of most of these methods becomes problematic when the background noise becomes high and the signal amplitude, frequency, or propagation velocity changes. In order to partially solve these problems, this paper proposes a new and simple method to determine the time-of-flight and center frequency of signals based on the use of zero-crossing times of filtered signals to calculate these parameters. Taking advantage of the idea that these zero-crossing times are concentrated around the maximum of the signal envelope, they were used as the time-of-flight of the signal. Together with the ToF, the center frequency of the signal was also determined. The proposed method was adapted to the processing of experimental signals obtained during various ultrasound investigations. By processing S₀ mode signals propagating in the sheet molding compound plate, the propagation velocity of this mode was calculated. Its value was compared with the value obtained by the 2D FFT method. The obtained results differed by 0.9%. Using simulated signals propagating in 1 mm-thick aluminum, the phase and group velocity segments of the A₀ mode were calculated. Their values differed by 0.7% from the theoretically calculated values of the dispersion curves by the SAFE method. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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18 pages, 5221 KiB

Open AccessArticle

Prediction Model for the Environmental Noise Distribution of High-Speed Maglev Trains Using a Segmented Line Source Approach

by Shiquan Cheng, Jianmin Ge, Longhua Ju and Yuhao Chen

Appl. Sci. 2025, 15(8), 4184; https://doi.org/10.3390/app15084184 - 10 Apr 2025

Viewed by 346

Abstract

Based on the theory of uniform finite-length incoherent line source radiation and real vehicle online test data of Shanghai Maglev trains, a prediction model for environmental noise is established using an equivalent segmented line sound source approach. The noise produced by Shanghai high-speed [...] Read more.

Based on the theory of uniform finite-length incoherent line source radiation and real vehicle online test data of Shanghai Maglev trains, a prediction model for environmental noise is established using an equivalent segmented line sound source approach. The noise produced by Shanghai high-speed Maglev trains running at speeds of 235, 300, and 430 km/h is tested and analyzed using microphones. The test data are combined with computational fluid dynamics simulations to divide the train’s sound sources equally into five sections. Theoretical calculations are carried out on the noise test data collected as the train passes by, and the source strength of each individual sub-sound source during the train operation is determined using the least-squares method. As a result, a prediction model for the environmental noise of high-speed Maglev trains, represented as a combination of multiple sources, is developed. The predicted results are compared with the measured values to validate the accuracy of the model. The proposed model can be used for environmental assessments before new train lines are launched, allowing for appropriate mitigation measures to be taken in advance to reduce the impact of Maglev noise on the surrounding residential and ecological environments. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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19 pages, 7262 KiB

Open AccessArticle

Comfortable Sound Design Based on Auditory Masking with Chord Progression and Melody Generation Corresponding to the Peak Frequencies of Dental Treatment Noises

by Masato Nakayama, Takuya Hayashi, Toru Takahashi and Takanobu Nishiura

Appl. Sci. 2024, 14(22), 10467; https://doi.org/10.3390/app142210467 - 13 Nov 2024

Viewed by 1100

Abstract

Noise reduction methods have been proposed for various loud noises. However, in a quiet indoor environment, even small noises often cause discomfort. One of the small noises that causes discomfort is noise with resonant frequencies. Since resonant frequencies are often high frequencies, it [...] Read more.

Noise reduction methods have been proposed for various loud noises. However, in a quiet indoor environment, even small noises often cause discomfort. One of the small noises that causes discomfort is noise with resonant frequencies. Since resonant frequencies are often high frequencies, it is difficult to apply conventional active noise control methods to them. To solve this problem, we focused on auditory masking, a phenomenon in which synthesized sounds increase the audible threshold. We have performed several studies on reducing discomfort based on auditory masking. However, it was difficult for comfortable sound design to be achieved using the previously proposed methods, even though they were able to reduce feelings of discomfort. Here, we focus on a pleasant sound: music. Comfortable sound design is made possible by introducing music theory into the design of masker signals. In this paper, we therefore propose comfortable sound design based on auditory masking with chord progression and melody generation to match the peak frequencies of dental treatment noises. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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17 pages, 3419 KiB

Open AccessArticle

Chromaticity Recognition Technology of Colored Noise and Operational Modal Analysis

by Xiangyu Lu, Huaihai Chen and Xudong He

Appl. Sci. 2024, 14(18), 8530; https://doi.org/10.3390/app14188530 - 22 Sep 2024

Viewed by 798

Abstract

Operational Modal Analysis (OMA) refers to the modal analysis with only output vibration signals of a structure in its operating state. Classic OMA has developed multiple recognition methods in both the time and frequency domains, where when the random excitation is unknown, the [...] Read more.

Operational Modal Analysis (OMA) refers to the modal analysis with only output vibration signals of a structure in its operating state. Classic OMA has developed multiple recognition methods in both the time and frequency domains, where when the random excitation is unknown, the excitation chromaticity is usually treated as white color, which can often cause errors and affect the accuracy of identifying frequencies or damping ratios. In this article, the chromaticity recognition function is defined and a method Chromaticity Recognition Technology (CRT) for identifying noise chromaticity based on system response is proposed. Then, a simulation example is presented. The noise chromaticity is identified for the response of the system under four types of colored noise excitation, and the results of the identification of operational mode parameters with and without CRT are compared. Furthermore, the sensitivity of traditional OMA to different colored noise has been investigated. An experiment with a cantilever under base excitation of pink noise has been undertaken and the results demonstrate the feasibility of the proposed CRT in this paper. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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27 pages, 8277 KiB

Open AccessArticle

High-Resolution Identification of Sound Sources Based on Sparse Bayesian Learning with Grid Adaptive Split Refinement

by Wei Pan, Daofang Feng, Youtai Shi, Yan Chen and Min Li

Appl. Sci. 2024, 14(16), 7374; https://doi.org/10.3390/app14167374 - 21 Aug 2024

Viewed by 1086

Abstract

Sound source identification technology based on a microphone array has many application scenarios. The compressive beamforming method has attracted much attention due to its high accuracy and high-resolution performance. However, for the far-field measurement problem of large microphone arrays, existing methods based on [...] Read more.

Sound source identification technology based on a microphone array has many application scenarios. The compressive beamforming method has attracted much attention due to its high accuracy and high-resolution performance. However, for the far-field measurement problem of large microphone arrays, existing methods based on fixed grids have the defect of basis mismatch. Due to the large number of grid points representing potential sound source locations, the identification accuracy of traditional grid adjustment methods also needs to be improved. To solve this problem, this paper proposes a sound source identification method based on adaptive grid splitting and refinement. First, the initial source locations are obtained through a sparse Bayesian learning framework. Then, higher-weight candidate grids are retained, and local regions near them are split and updated. During the iteration process, Green’s function and the source strength obtained in the previous iteration are multiplied to get the sound pressure matrix. The robust principal component analysis model of the Gaussian mixture separates and replaces the sound pressure matrix with a low-rank matrix. The actual sound source locations are gradually approximated through the dynamically adjusted sound pressure low-rank matrix and optimized grid transfer matrix. The performance of the method is verified through numerical simulations. In addition, experiments on a standard aircraft model are conducted in a wind tunnel and speakers are installed on the model, proving that the proposed method can achieve fast, high-precision imaging of low-frequency sound sources in an extensive dynamic range at long distances. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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22 pages, 6169 KiB

Open AccessArticle

Design of Robust Broadband Frequency-Invariant Broadside Beampatterns for the Differential Loudspeaker Array

by Yankai Zhang, Hongjian Wei and Qiaoxi Zhu

Appl. Sci. 2024, 14(14), 6383; https://doi.org/10.3390/app14146383 - 22 Jul 2024

Cited by 1 | Viewed by 1148

Abstract

The directional loudspeaker array has various applications due to its capability to direct sound generation towards the target listener and reduce noise pollution. Differential beamforming has recently been applied to the loudspeaker line array to produce a broadside frequency-invariant radiation pattern. However, the [...] Read more.

The directional loudspeaker array has various applications due to its capability to direct sound generation towards the target listener and reduce noise pollution. Differential beamforming has recently been applied to the loudspeaker line array to produce a broadside frequency-invariant radiation pattern. However, the existing methods cannot achieve a compromise between robustness and broadband frequency-invariant beampattern preservation. This paper proposed a robust broadband differential beamforming design to allow the loudspeaker line array to radiate broadside frequency-invariant radiation patterns with robustness. Specifically, we propose a method to determine the ideal broadside differential beampattern by combining multiple criteria, namely null positions, maximizing the directivity factor, and achieving a desired beampattern with equal sidelobes. We derive the above ideal broadside differential beampattern into the target beampattern in the modal domain. We propose a robust modal matching method with Tikhonov regularization to optimize the loudspeaker weights in the modal domain. Simulations and experiments show improved frequency-invariant broadside beamforming over the 250–4k Hz frequency range compared with the existing modal matching and null-constrained methods. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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20 pages, 9785 KiB

Open AccessArticle

Evaluation of Noise-Reduction Techniques for Gas-Turbine Test Stands: A Preliminary Analysis

by Laurentiu Cristea and Marius Deaconu

Appl. Sci. 2024, 14(13), 5702; https://doi.org/10.3390/app14135702 - 29 Jun 2024

Cited by 1 | Viewed by 1691

Abstract

Emphasizing the importance of acoustic attenuation in maintaining compliance with stringent noise regulations and enhancing workplace safety, this analysis covers theoretical and practical aspects of prediction methods used for the development of sound attenuators for gas-turbine testing stands. This paper presents a preliminary [...] Read more.

Emphasizing the importance of acoustic attenuation in maintaining compliance with stringent noise regulations and enhancing workplace safety, this analysis covers theoretical and practical aspects of prediction methods used for the development of sound attenuators for gas-turbine testing stands. This paper presents a preliminary analysis and evaluation of the improvement of the Embleton method for projecting a noise attenuator for industrial applications, especially for gas-turbine test stands. While primarily focusing on the static acoustic behavior of the attenuator, certain considerations were also made regarding flow conditions, Mach number-dependent attenuation, pressure drop, and self-generated noise aspects to provide a comprehensive perspective on applying a suitable evaluation method. The study investigates different calculation methods for the assessment of noise reduction for linear and staggered baffles applied on a scaled reduced model of an attenuator. Thus, the critical parameters and development requirements necessary for effective noise reduction in high-performance gas-turbine testing environments will be evaluated in a downscaled model. Key factors examined include the selection of design parameters and configurations from various topological options (single, double, and triple parallel baffles vs. double and triple staggered baffles). Advanced computational methods, like analytic and finite-element analysis (FEM), are used to predict acoustic performance and evaluate the prediction method. Experimental validation is performed to corroborate the simulation results, ensuring the reliability and efficiency of the attenuator. The results indicate that an improved prediction method led to a better design for a sound-attenuator module, which can significantly reduce noise levels without compromising the operational performance of the gas turbine inside a test cell. Full article

(This article belongs to the Special Issue Noise Measurement, Acoustic Signal Processing and Noise Control)

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