Experimental evaluation of vehicle cabin noise from suspension induced vibrations using transfer path and psychoacoustic analysis techniques

Given the automotive industry\u27s awareness of the importance of the perception of NVH emissions, there is an increased focus on the psychoacoustics, or sound quality, of vehicle cabin noise. The present work aims to qualitatively evaluate and compare automobile cabin noise by measuring the road-induced noise and vibration of a driven and motored vehicle. Evaluation of transmission paths and psychoacoustic analysis of the cabin acoustics are primary objectives. A psychoacoustic analysis using the acoustic pressure measurements taken inside the vehicle cabin was performed using both subjective and objective approaches. Testing also included vibration measurements from several structural positions to evaluate vibroacoustic excitations. Using this noise and vibration data, it was possible to evaluate the transfer path of the excitation energy into the vehicle cabin. Further, an attempt to establish a correlation between the noise and vibration measurements and the psychoacoustic observations was also proven possible with some inherent limitations

Objective Predictor metric of Annoyance for Hydraulic Engine Mount Cavitation

Vehicle acoustics has been found to have a direct impact on customer experience. Unexpected noises play a role in this experience. Hydraulic engine mount cavitation, the noise heard from the collapse of vapor bubbles in the mount, is considered one of those unexpected noises. During the design phase of a vehicle when an unexpected noise is found there is a need for a method to quantify how much of the noise is too much. Subjective evaluations alone are not enough due to variability from engineer to engineer. An objective way needed to be developed in order to evaluate the cavitation noise. To address this issue, an objective predictor metric of annoyance was developed. The model was developed by comparing psychoacoustic metrics to subjective ratings by means of regression analysis. Once the psychoacoustic metrics were chosen multiple regression analysis was used to develop the predictor metric

차량의 스포티한 엔진음 정량화를 위한 음질 지수 개발과 그 정확도 향상을 위한 방법 연구

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계항공공학부, 2020. 8. 강연준.Developments in vehicle technology and accompanying improvements in NVH performance have led to increased consumer demand for high sound quality, such as a sporty engine sound. As sporty sound is subjective, this thesis sought to express its meaning quantitatively and to develop a model that accommodates the differences in individuals tastes. This thesis tackles two main issues. The first is to identify the efficiency of factor analysis for utilizing it in developing a sound quality index of sportiness. The second is to further improve the accuracy of the sound quality index and to refine the definition of sportiness by adding K-means cluster analysis. In Chapter 2 and 3, the initial procedure for developing the sportiness index is presented. Accordingly, the process of recording the vehicles interior operating sound under wide open throttle acceleration conditions for 4 different vehicles and producing 13 evaluation samples by using parametric band-pass filtering is described. Acoustic and psychoacoustic parameters of the samples produced were calculated, and the preferences for sportiness were identified through jury testing. Jury test was jointly carried out by 23 evaluators and a semantic differential method was used to find adjectives that could explain the concept and preference for sportiness. The Sportiness index was developed using factor analysis and multiple linear regression analysis between the calculated values and the previously collected jury test results. The index was then validated by examining the correlation coefficient through a new sample group. Furthermore, the necessity of factor analysis for the sportiness index development was concluded. In Chapter 4, after K-means clustering, factor and multiple linear regression analysis were repeated to develop a model reflecting differences for each group in evaluators tastes. The improved index was also retested using new evaluators and new samples, demonstrating its reliability through the high correlation observed in the validation studies. This sound quality evaluation index is useful for producing highly accurate results and reflecting the opinions of groups expressing a variety of commonalities.현재 차량 개발 기술이 발전함에 따라 차량의 NVH 성능이 많이 개선되었고, 이로 인해 소음 저감의 측면보다 듣기 좋은 소리와 같은 음질 측면에서의 소비자의 수요가 계속해서 증가하고 있다. 스포티한 엔진음이 그 범주에 속하고, 이는 사람마다 떠올리는 이미지가 다르고 소리에 대한 취향의 차이가 발생하는 주관적인 개념이다. 따라서 본 연구는 음질 연구를 통해서 그러한 개념의 객관적인 의미를 찾아 정량적으로 표현하고, 취향의 차이가 발생하는 것을 수용할 수 있는 방법을 찾기 위해 진행되었다. 본 논문에서 중점적으로 다루는 내용은 크게 두 가지이다. 첫 번째는, 스포티함의 음질 지수를 개발함에 있어 요인 분석을 활용함으로써 요인 분석의 효율성을 확인하고자 한 것이고, 두 번째는, K-평균 군집 분석을 추가하여 음질 지수의 정확도를 더 향상시키고 스포티함의 의미를 더욱 구체화하고자 한 것이다. 따라서, 본 논문의 2장과 3장에서는, 양산되고 있는 차량 4대를 wide open throttle 조건에서 엔진음을 녹음하였고, 녹음된 소리로부터 parametric band-pass filter를 사용해 신호를 변조하여 13개의 샘플을 제작하였다. 제작된 샘플의 음향심리학적 매개변수들을 계산하였고, 청음 평가를 통해서 스포티함에 대한 선호도를 파악하였다. 청음 평가는 23명의 평가자가 참여하였고, 의미미분법을 사용해 스포티함의 선호도와 스포티함을 잘 설명할 수 있는 형용사들을 찾아냈다. 그 결과를 요인 분석에 적용해 사람들이 공통적으로 느끼는 스포티함의 특성을 두 요인으로 표현하였고, 평가 결과 간 다중 선형 회귀 분석을 이용해 관련된 음질 인자로 표현할 수 있는 스포티함 정량화 지수를 개발하였다. 개발된 지수는 새로운 샘플군을 통해 상관계수를 확인하여 그 유효성이 확인되었다. 또한, 요인 분석 사용 유무에 따른 회귀식의 결과를 비교함으로써 요인 분석의 필요성에 대해서도 언급하였다. 4장에서는, 스포티함에 대한 평가자들의 성향 차이가 발생하는 것을 토대로 K-평균 군집 분석을 활용해 각 집단에 맞는 회귀식을 개발하기 위해 요인 분석과 다중선형회귀 분석을 재수행하였다. 개발된 지수의 신뢰성을 역시 확보하기 위해 새로운 평가자들로 재검사하였고 높은 상관계수를 토대로 그 신뢰성을 입증하였다. 결과적으로, 본 연구를 통해 개발된 음질 평가 지수는 스포티함을 객관적으로 정의함에 있어 또 다른 공통성을 나타내는 집단의 의견까지도 반영할 수 있고 정확도 높은 결과를 산출해주는 유용한 지수이다.CHAPTER 1 INTRODUCTION 1 CHAPTER 2 SOUND QUALITY EVALUATION OF VEHICLE ENGINE SPORTINESS 6 2.1 Introduction 6 2.2 Sound recording and objective evaluation of engine sound 7 2.2.1 Recording of interior sound 7 2.2.2 Production of sound samples 12 2.2.3 Calculation of objective acoustic and psychoacoustic parameters 16 2.2.3.1 Sound pressure level 18 2.2.3.2 Loudness 19 2.2.3.3 Sharpness 20 2.2.3.4 Roughness 21 2.2.3.5 Tonality 22 2.3 Subjective evaluation of sound quality 23 2.3.1 Semantic differential method and pre-test 23 2.3.2 Jury testing 26 CHAPTER 3 DEVELOPMENT OF EVALUATION INDEX OF SPORTY ENGINE SOUND : USING FACTOR ANALYSIS 32 3.1 Introduction 32 3.2 Factor analysis 33 3.3 Regression analysis 42 3.3.1 Multiple linear regression 42 3.3.2 Development of a sound quality index for sportiness 44 3.4 Validation 50 3.5 Summary 55 CHAPTER 4 NEW APPROACH TO DEVELOPMENT OF EVALUATION INDEX OF SPORTY ENGINE SOUND : USING K-MEANS CLUSTER ANALYSIS 57 4.1 Introduction 57 4.2 Statistical analysis 59 4.2.1 K-means cluster analysis 59 4.2.2 Factor analysis after K-means clustering 66 4.2.3 Regression analysis after K-means clustering 71 4.3 Validation 78 4.4 Summary 83 CHAPTER 5 CONCLUSIONS 86 REFERENCES 89 APPENDIX 98 국 문 초 록 102Docto

Review of active noise control techniques with emphasis on sound quality enhancement

The traditional active noise control design aims to attenuate the energy of residual noise, which is indiscriminative in the frequency domain. However, it is necessary to retain residual noise with a specified spectrum to satisfy the requirements of human perception in some applications. In this paper, the evolution of active noise control and sound quality are briefly discussed. This paper emphasizes on the advancement of active noise control method in the past decades in terms of enhancing the sound quality

Investigating Perceptual Congruence Between Data and Display Dimensions in Sonification

The relationships between sounds and their perceived meaning and connotations are complex, making auditory perception an important factor to consider when designing sonification systems. Listeners often have a mental model of how a data variable should sound during sonification and this model is not considered in most data:sound mappings. This can lead to mappings that are difficult to use and can cause confusion. To investigate this issue, we conducted a magnitude estimation experiment to map how roughness, noise and pitch relate to the perceived magnitude of stress, error and danger. These parameters were chosen due to previous findings which suggest perceptual congruency between these auditory sensations and conceptual variables. Results from this experiment show that polarity and scaling preference are dependent on the data:sound mapping. This work provides polarity and scaling values that may be directly utilised by sonification designers to improve auditory displays in areas such as accessible and mobile computing, process-monitoring and biofeedback

CPX based synthesis for binaural auralization of vehicle rolling noise to an arbitrary positioned stander-by receiver

Virtual reality is becoming an important tool for studying the interaction between pedestrians and road vehicles, by allowing the analysis of potentially hazard situations without placing subjects in real risk. However, most of the current simulators are unable to accurately recreate traffic sounds that are congruent with the visual scene. This has been recognized as a fault in the virtual audio-visual scenarios used in such contexts. This study proposes a method for delivering a binaural auralization of the noise generated by a moving vehicle to an arbitrarily located moving listener (pedestrian). Building on previously developed methods, the proposal presented here integrates in a novel way a dynamic auralization engine, thus enabling real-time update of the acoustic cues in the binaural signal delivered via headphones. Furthermore, the proposed auralization routine uses Close ProXimity (CPX) tyre-road noise signal as sound source input, facilitating the quick interchangeability of source signals, and easing the noise collection procedure. Two validation experiments were carried out, one to quantitatively compare field signals with CPX-derived virtual signal recordings, and another to assess these same signals through psychoacoustic models. The latter aims to assure that the reproduction of the synthesized signal is perceptually similar to one occurring on pedestrian/vehicle interactions during situations of street crossing. Discrepancies were detected, and emphasized when the vehicle is within close distance from the receiver (pedestrian). However, the analysis indicated that these pose no hindrance to the study of vehicle–pedestrian interaction. Improvements to the method are identified and further developments are proposed.This work was supported by the ‘‘Fundação para a Ciência e a Tecnologia” [PTDC/ECM-TRA/3568/2014, SFRH/BD/131638/2017, UIDB/04029/2020] This work is part of the activities of the research project AnPeB – ‘‘ANalysis of PEdestrians Behaviour based on simulated urban environments and its incorporation in risk modelling” (PTDC/ECM TRA/3568/2014), funded by the ‘‘Promover a Produção Científica e Desenvolvimento Tecnológico e a Constituição de Redes Temáti cas” (3599-PPCDT) project and supported by the ‘‘European Com munity Fund FEDER” and the doctoral scholarship SFRH/ BD/131638/2017, funded by ‘‘Fundação para a Ciência e a Tecnolo gia (FCT)”

Squeak and Rattle Prediction for Robust Product Development

Squeak and rattle are nonstationary, irregular and impulsive sounds that happen inside the car cabin. For decades, customer complaints about squeak and rattle have been, and still are, among the top quality issues in the automotive industry. These annoying sounds are perceived as quality defect indications and burden warranty costs to the car manufacturers. Today, the quality improvements regarding the persistent type of sounds in the car, as well as the increasing popularity of electric engines, as green and quiet propulsion solutions, stress the necessity for suppressing annoying sounds like squeak and rattle more than in the past. The technical solution to this problem is to approach it in the pre-design-freeze phases of the product development and by employing design-concept-related practises. To nail this goal, prediction and evaluation tools and methods are needed to deal with the squeak and rattle quality issues upfront in the product development process. The available tools and methods for prediction of squeak and rattle sounds in the pre-design-freeze phase in a new car development process are not yet sufficiently mature. The existing knowledge gap about the mechanisms behind the squeak and rattle sounds, the lack of accurate simulation and post-processing methods, as well as the computational cost of complex simulations are some of the significant hurdles in this immaturity. This research addresses this problem by identifying a framework for prediction of squeak and rattle sounds in the form of a cause and effect diagram. The main domains and the elements and the sub-contributors to the problem in each domain within this framework are determined through literature studies, field explorations and the conducted descriptive studies on the subject. Further, improvement suggestions for the squeak and rattle evaluation and prediction methods are proposed through prescriptive studies. The applications of some of the proposed methods in the automotive industry are shown and examined in industrial problems