Query: The prediction of low- and mid-frequency internal road vehicle noise: A literature survey

title: The prediction of low and mid frequency internal road vehicle noise: A literature survey
abstract: Over the past 40 years the low and mid frequency internal noise of road vehiles has been of increasing interest to both manufacturers and customers, and there have been many papers written on the subject. It is particularly important that manufacturers are able to predict the noise at an early stage of a new design so that expensive mistakes can be avoided. This paper reviews the relevant literature published over this 40 year period and concludes that the finite element method (FEM) and/or the boundary element method (BEM) are currently the most accurate ways of predicting this noise. However, although the emphasis of this review is on the low and mid frequency structure borne aspect of the noise, other prediction methods (which are normally considered to be only applicable at high frequencies) are also considered. In particular, the statistical energy analysis (SEA) is shown to be an increasingly useful tool for predicting structure borne noise, as is the newly developed FEM/SEA hybrid method. Other essentially high frequency techniques are also considered in this review because recent research indicates that it might be possible to apply these methods over a broader frequency range than was initially envisaged.

title: Noise source characteristics in the ISO 362 vehicle pass by noise test Literature review
abstract: Since many people are exposed to road traffic noise in urban areas, current legislation aims to limit vehicle noise emissions. In Europe, the vehicle pass by noise test is implemented according to the international standard ISO 362. As a result of more recent investigations of urban traffic, a revision to the ISO 362 standard has been proposed that includes a constantspeed test in addition to the traditional accelerated test in order to determine the pass by noise value. To ensure compliance with the pass by noise test vehicle manufacturers and suppliers must quantify vehicle noise source characteristics during the design stage of the vehicle. In addition, predictive tools need to be available during the product development phase in order to estimate the final pass by noise level. In this paper an extensive literature survey is presented of noise source characteristics in the ISO 362 vehicle pass by noise test. Vehicle pass by noise is analysed in the time and frequency domains and a ranking of the noise source contributions is established. The characteristics of the four major noise sources (engine, intake system, exhaust system, tyre/road system) contributing to pass by noise as well as current prediction methods are reviewed.

title: PREDICTION OF LOW FREQUENCY TRAFFIC NOISE FOR BUILDING VIBRATION STUDIES
abstract: Vibrations induced in buildings by road traffic have been the subject of research in the UK for a number of years. Recent attention has focussed on the large contribution which low frequency traffic noise levels commonly make to these vibrations. Moreover, it has recently been shown that building structures can be calibrated in terms of their internal vibratory response to external low frequency noise. However, to date, there has been no precise method available for predicting external one third octave band low frequency traffic noise levels for use in building vibration studies. This paper describes a study into the prediction of low frequency traffic noise, some of the results of which have been used to develop such a prediction method. The equations developed are tested against measured levels from a variety of authors and shown to be accurate. One third octave band levels are shown to be less predictable than broader band vibratory disturbance scales. The prediction method is also evaluated against an approximate interim method used by one overseas authority to date. It is shown that large prediction errors can arise with this interim method, especially if different heavy vehicle categories are not accounted for.

title: Separating the contributions from air pumping and tyre vibrations by speed dependency analysis of tyre/road noise
abstract: Traditionally tyre/road noise has been divided into low mid frequency noise caused by tyre vibrations and high frequency noise caused by various air flow related mechanisms, "air pumping" It has also been assumed that these two processes grow in importance with different (vehicle) speed exponents. The purpose with this work is to investigate how to extract the different noise sources by a speed exponent analysis. Such analysis tool would e.g. indicate under which circumstances it is necessary to include air flow related sources in a tyre/road noise prediction model. The results show that it is possible to extract components of tyre/road noise that grow with the speed to the power of two and four. Expecting these contributions to be connected to tyre vibrations and air flow related source mechanisms respectively, it is found that the latter are present at surprisingly low frequencies. In addition, modelled results, only taking into account noise created by tyre vibrations, also show speed exponents larger than two. It is concluded that tyre vibrations can generate noise with a range of speed exponents making it futile to separate the two main tyre/road noise source mechanisms by a speed exponent analysis.

title: Noise source characteristics in the ISO 362 vehicle pass by noise test: Literature review
abstract: Since many people are exposed to road traffic noise in urban areas, current legislation aims to limit vehicle noise emissions. In Europe, the vehicle pass by noise test is implemented according to the international standard ISO 362. As a result of more recent investigations of urban traffic, a revision to the ISO 362 standard has been proposed that includes a constant speed test in addition to the traditional accelerated test in order to determine the pass by noise value. To ensure compliance with the pass by noise test vehicle manufacturers and suppliers must quantify vehicle noise source characteristics during the design stage of the vehicle. In addition, predictive tools need to be available during the product development phase in order to estimate the final pass by noise level. In this paper an extensive literature survey is presented of noise source characteristics in the ISO 362 vehicle pass by noise test. Vehicle pass by noise is analysed in the time and frequency domains and a ranking of the noise source contributions is established. The characteristics of the four major noise sources (engine, intake system, exhaust system, tyre/road system) contributing to pass by noise as well as current prediction methods are reviewed.

title: A Road Test of the Luxury Car Tax Concession: Will It Influence Demand for Low Carbon Vehicles?
abstract: The Australian Government proposes to reduce greenhouse gas emissions from the road transport sector by phasing in regulatory fuel efficiency standards between 2020 and 2025. To meet the standards, global car manufacturers will be required to reduce their fleets' average CO2 emissions by increasing the supply of low emitting, fuel efficient vehicles. The Australian Government states the luxury car tax (LCT) concession for fuel efficient vehicles is one of the adopted measures to encourage "households and businesses" to purchase more fuel efficient vehicles. A study was conducted to examine the role of the LCT concession in influencing consumer demand for more fuel efficient vehicles. For each vehicle type segment, this study categorised vehicles into pairs, one classified by the National Transport Commission as having "best in class emissions" and the other as "best in sales" The study aimed to quantify the impact of the LCT concession and the LCT regime on consumer demand by examining the cost price and vehicle sales for each vehicle pair. The findings from the survey, together with analysis of the policy measure and a literature review, could not support the Australian Government's assertion that the LCT concession encourages consumers to purchase more fuel efficient vehicles. According to the literature, the most important barrier to low emitting vehicles is their high price compared to internal combustion engine (ICE) vehicles. The study findings provide grounds for policymakers to reform the LCT regime and the LCT concession a reform that is required to support the introduction of regulatory fuel efficiency standards to aid in the reduction of road transport emissions.

title: Maneuver Prediction for Road Vehicles Based on a Neuro Fuzzy Architecture With a Low Cost Navigation Unit
abstract: Collision avoidance is currently one of the main research areas in road intelligent transportation systems. Among the different possibilities available in the literature, the prediction of abrupt maneuvers has been shown to be useful in reducing the possibility of collisions. A supervised version of dynamic Fuzzy Adaptive System ART based (dFasArt) which is a neuronal architecture based method that employs dynamic activation functions determined by fuzzy sets, is used for maneuver predicting and solving the problem of intervehicle collisions on roads. In this paper, it is shown how the dynamic character of dFasArt minimizes problems caused by noise in the sensors and provides stability on the predicted maneuvers. Several experiments with real data were carried out, and the SdFasArt results were compared with those achieved by an implementation of the Incremental Hierarchical Discriminant Regression (IHDR) based method, showing the suitability of SdFasArt for maneuver prediction of road vehicles.

title: Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines
abstract: This Thesis is focused on the development and implementation of general and efficient numerical methods for the acoustic modelling and design of noise control devices in the exhaust system of combustion engines. Special attention is paid to silencers, that can be divided into reactive and dissipative configurations. For the latter, significant differences are likely to appear in their acoustic behaviour, depending on the temperature variations within the absorbent material. Also, material heterogeneities associated with uneven filling processes and time degradation due to the exhaust gases, can alter the silencer attenuation performance. Therefore, numerical techniques considering all these features are required to guarantee an accurate prediction of the acoustic behaviour. First, a literature review is carried out. This is mainly related to one dimensional models and their associated matrix representation, as well as to acoustic models for absorbent materials and perforated surfaces. It is worth noting that plane wave model limitations make indispensable using alternative multidimensional methods, since the latter are valid for a wide frequency range and for silencers with complex geometries. In addition to developing acoustic models to simulate exhaust silencers in general terms, the possibility of using new acoustic elements is also explored in this Thesis. These elements have as an objective being an interesting potential alternative to the fibrous absorbent materials commonly used in practice, whose negative impact on health is a current cause for concern. In this sense, and following earlier studies, the Thesis considers the use of microperforated surfaces and goes into detail about the study of surfaces manufactured by sintering. The latter present, in some cases, the particularity of having a nearly constant acoustic impedance, whose value depends, among others, on the thickness and porosity of the plates. Both kind of surfaces have been proved to be an interesting alternative to dissipative silencers; the microperforated surfaces in the low frequency range and the sintered screens in the mid and high frequency range. General acoustic models, in which the wave equation permits to consider variable properties and mean flow, are considered. Thus, a finite element approach is first

title: Road Traffic Noise under Heterogeneous Traffic Condition in Makassar City, Indonesia
abstract: In recent years, the increase of vehicle number in developing countries including Indonesia leads the rise of road traffic noise (RTN) and the RTN becomes a serious problem on living environment. Therefore, a research to abate the RTN is important. Regarding this, the authors start to study the characteristics and prediction method of RTN in Indonesia. As the first step, this paper shows the present condition of RTN in Makassar City as an example city in Indonesia. The surveys on RTN, traffic conditions, and vehicle horns are carried out at thirty five main roads. The results show that the noise levels exceed 70 dB, the highest value of the Environmental Standard for Noise in Indonesia. Then, the authors try to predict the equivalent continuous A weighted sound pressure level (LAeq) under the heterogeneous traffic condition by using the ASJ RTN Model 2008. There are some differences between the measured LAeq and the predicted ones. An idea to predict the RTN by considering the low speed steady traffic flow and the horn sounds are presented, and the results show a moderate good prediction. However further research work is needed to predict the RTN more precisely and to find the method to abate the RTN in Makassar.

title: Relationship between frequency shifting of vehicle sounds and acceleration impression
abstract: Pioneer Corporation,25 1 Aza Nishimachi, Yamada, Kawagoe, 350 8555 Japan(Received 22 May 2014, Accepted for publication 7 August 2014)Keywords: Vehicle sound, Acceleration impression, Frequency shifting, Paired comparison, Subjective evaluationPACS number: 43.50.Lj, 43.66.Hg, 43.66.Lj [doi:10.1250/ast.36.135]1. IntroductionThe use of vehicles that are propelled in whole or in partby electric motors, such as electric vehicles (EV) or hybridelectric vehicles (HEV) is becoming increasingly common inurban fleets. Many types of EV/HEVs emit less sound thanconventional internal combustion engine vehicles (ICEVs),particularly when they are driven at a low speed. It has been amatter of concern that the quietness of EV/HEVs may createdangerous situations for pedestrians, because they sometimescannot hear the sound of such vehicles in an urban soundenvironment  Hence, regulations and recommendationsthat will mandate or recommend the installation of additionalsound emitting devices in quiet vehicles are being consideredby some governments/organizations, such as the UnitedStates, Japan, and the World Forum for Harmonization ofVehicle Regulations (UNECE/WP.29) According to a guide line [2] a warning sound should be automatically generatedwhen the vehicle is driven at a speed of less than 20km/h.This is because the difference between the sound level of anEV/HEV and an ICEV is significant in this speed range andthe tire road noise becomes dominant at higher speeds.When the sound is designed, it should not be a simpleimitation of a conventional gasoline engine sound. Accordingto a questionnaire on the sound of EV/HEVs  conven tional engine sounds are not the best means to identify avehicle's presence and behavior in an urban sound environ ment. In the survey, more than 50% of the respondentswho drove their cars daily replied that, as drivers, they hadexperienced a sense of danger owing to pedestrians' lackof awareness of their cars. In contrast, only 1.6% of therespondents owned and drove HEVs.It is crucial to reveal the appropriate design of the sounds.For pedestrians, it is important to know the necessary soundlevel to give sufficient warning of an approaching vehicle inan urban environment. The authors have conducted a series ofstudies [4 6] to discuss the feasible sound level of the sound.There has also been some research concerning the temporaland spectral properties of such a sound.