Jae-Eun Jeong

Sound Quality Evaluation for Laundry Noise by a Virtual Laundry Noise Considering the Effect of Various Noise Sources in a Drum Washing Machine

The objective of this study is to determine the effect for the sound quality according to the noise source and to build the sound quality index of the laundry noise. In order to compare laundry noise among the influence of noise sources, we made virtual laundry noises by synthesizing an actual laundry noise and each noise source such as a dropping noise, water noise, motor noise and circulation pump noise. We conducted a listening test by customers using virtual laundry noises. As a result of listening test, we found that the dropping noise has a decisive effect on the sound quality of the laundry noise. We conducted the multi regression analysis of sound quality for the laundry noise using the statistical data processing. It is verified to the reliability of the multi regression index by comparison with listening results and index results of other actual laundry noises. This study is expected to provide a guide line for improvement of the laundry noise.

Evaluation of Vehicle Seat Rattle Noise Using Coherence Function Technique

Recently, customers have been concerned about vehicle NVH depending on vehicle designing and manufacturing technologies development. In choosing vehicle, vehicle NVH is becoming the most important factor to customers. Especially, a seat is the final stage of vibration transfer path to passengers from all sources of vibration like engine, transmission and etc. And seat is the nearest component from driver`s ear. For this reason, seat is the most important component that directly related to ride comfort for passengers. And driver can be influenced sensitively by BSR caused by seat. Thus, evaluating the vibration characteristics of vehicle seat and BSR caused by vehicle seat is necessary to reduce the seat BSR. The rattle noise occurred from seat has evaluated through sound source visualization and multi-dimensional spectral analysis - coherence function technique in this paper. Vibration characteristics of the seat has verified through modal test.

Noise Reduction of PDP TV Using Multi-dimensional Spectral Analysis Method

The method is introduced for estimating the noise source contribution on the noise of PDP TV in a multiple-input system where the input sources may be coherent with each other. By the coherence function method, it is found that the biggest part of the noise source in the PDP TV noise is generated by the PCB boards which consume high power and produce high heat. This analysis is modeled as three-input/single-output system because the noise is generated by three main boards, X-board, Y-board, SMPS that are located close to each other. The coherence function method is proved to be useful tool for identifying of noise source. In this study, Transfer Path Analysis using MDSA is implemented to determine the quantitative noise contribution of each board for PDP TV with the rear case closed and with the rear case open. And the possibility of noise reduction is confirmed through the experimental method that isolates the most contributing board by adding sound-absorbing materials to it.

Sound Quality Evaluation Based on the Mahalanobis Distance for the Interior Noise of Driving Vehicles with Various the Tire Type

The reduction of vehicle interior noise has been the main interest of NVH engineers. The drivers perception of the vehicle noise is strongly affected by the psychoacoustic characteristics of the noise and the SPL. The existing methods to evaluate the SQ for vehicle interior noise are linear regression analysis of subjective SQ metrics by statistics and the estimation of subjective SQ values by neural network. However, these methods strongly depend on jury tests, this leads to difficulties. To reduce the important of the jury tests, we suggest a new method using the Mahalanobis distance for SQ evaluation. And, the optimal characteristic values that influenced the results of sound quality evaluation on the basis by main effect. Finally, we developed a new method based on the MD method to evaluate sound quality. The result of noise evaluation revealed that the sound quality could be well improved by changing the structural characteristics of the vehicle.

Case study for Sound Quality Index of Vacuum Cleaner` Operating Noise

The conventional noise control attempts to simply reduce the level of product noise. But it is very straight forward way that we have considered human perception on noise. Since human listening is very sensitive to sound. Evaluation of the sound quality of a vacuum cleaner is studied base on human sensibility engineering. In this paper, we choose six vacuum cleaners that are sold in Korea and reduced noise control. The sound quality of vacuum cleaner noise is analyzed by employing the subjective evaluation and by representing them in terms of the objective quantities. Semantic differential method is used to study sound quality Evaluation. To analyze the sound quality of vacuum cleaner noise, consider the coefficients of correlation between sound metrics and subjective rating. The linear regression models were obtained for the subjective evaluation and sound quality metrics.

Transfer Path Analysis of Output Noise Using Multi-dimensional Spectral Analysis Method for Vacuum Cleaner

Noise reduction of vacuum cleaner is important, according as get into standard that estimate quality of product. To reduce noise of vacuum cleaner, we need analysis of correct noise source and contribution grasping about Identified noise sources` output noise. Because noise sources` correlation exists in vacuum cleaner that is small and complicated system, analysis is not easy. In this case, we need to apply Multi-dimensional spectral analysis(MDSA) method that can remove correlation between noise sources and grasp pure contribution degree of noise sources. In this study, we take transfer path analysis between output noise and noise that measured in inside/outside of vacuum cleaner.

Evaluation of the Inputs Efficiency for the Interior Noise of the Vehicle using Vector Synthesis Method

A passenger vehicle has various and complicated transmission paths of sound and vibration. In order to identify the mechanism of transfer path, estimation of excitation force and exact modeling of transfer path are required. In this paper vector synthesis technique is employed to identify the characteristics of road noise and its transmission to vehicle compartment through noise and vibration analysis. Vibration reduction efficiency of each transfer path is evaluated by comparing individual vector components obtained virtual simulation. The degree of effect is used to estimate the contribution of vibration input components to total output. And in this paper presents a new technique based on simulation studies using vector synthesis diagram and design of experiments, by which the effects of magnitude and phase change of input paths can be predicted.

A Newly Advanced Anti-Vibration Pad With a Phase Balancer Designed by Analysis of Washing Machine Behaviors

This study proposed an anti-vibration pad with a phase balancer that helps reduce wood floor vibrations from a washing machine as well as the vibrations of the machine itself. When a washing machine is installed just on anti-vibration pads, the floor vibrations can be reduced, but consequently the machine’s left–right vibrations become more violent. Accordingly, in order to identify the mechanism by which anti-vibration pads generate left-right vibrations in washing machines, the present study proposed a two-point measurement method that can determine vertical washing machine vibrations and phase differences. In addition, we proposed an optimal phase balancer designed by a finite element analysis-based response surface method for reducing vibrations using a phase difference. As a result, the anti-vibration pad with a phase balancer, when applied to washing machines, greatly contributed to simultaneously reducing the actual vibrations of washing machines and the vibration transfer to the floor.

Weight Lightening of HUMS Housing for Small Aircraft by Using FEM and Taguchi Method

It is true that the dependency on import is currently high in case of the safety checkup system of domestic airplanes, and it is at the point of time that localization of HUMS for small airplanes is required. In this study, the design factors were selected for the lightweight of HUMS for small air- planes by using Pro-Engineer which is a design tool and Abaqus. 9 models were made through ex- periment plans with Taguchi method for this, and the each model for weight lightening was selected through vibration analysis and shock analysis while in operation with experiment profile values. After fabricating HUMS, it was verified that as a result of experiment with the same profile values as the analysis, there was similarity between the analyzed values and values of the experiment. As a result of performing weight lightening which is the purpose of the study, electronic performance for small airplanes is assured and a design plan reducing 15 % weight compared to the targeted weight was deduced. Besides, it could be verified that the light weight model satisfied the maximum allowable displacement value of PCB(printed circuit board) and accordingly satisfied electronic properties of HUMS. In this study, the reliability of a product was certified through the result of an experiment on ground. If the reliability of HUMS were verified through a test flight in the future, it is consid- ered that it would make a big contribution to localization of aerospace electronic equipment.

Noise Source Identification of Electric Parking Brake by Using Noise Contribution Analysis and Identifying Resonance of Vehicle System

Caliper intergrated Electric Parking Brake (EPB) is an automatic parking brake system, attached to rear caliper. Because EPB uses luxury vehicles recently, the drivers of vehicles are sensitive to the EPB noise. EPB is operated by the motor and gear, so noise is generated by motor and gear. In order to reduce noise, One of EPB manufacturers uses helical gear and changes the shape of EPB housing. But these methods are not optimized for reduction of interior noise. There are many noise transfer paths into vehicle interior and it is difficult to identify the noise sources. Therefore, in this study, we performed contribution analysis and modal testing in the vehicle system. It is possible to distinguish between air-borne noise and structure-borne noise in the vehicle interior noise by comparing interior noise peak with resonance mode map.