Browse Topic: Exterior noise
ABSTRACT Awareness of the surroundings is strongly influenced by acoustic cues. This is of relevance for the implementation of safety strategies on board of electric and hybrid vehicles and for the development of acoustic camouflage of military vehicles. These two areas of research have clearly opposite goals, in that developers of electric vehicles aim at adding the minimum amount of exterior noise that will make the EV acoustically noticeable by a blind or distracted pedestrian, while the developers of military vehicles desire to implement hardware configurations with minimum likelihood of acoustic detectability. The common theme is the understanding of what makes a vehicle noticeable based the noise it generates and the environment in which it is immersed. Traditional approaches based on differences of overall level and/or one-third octave based spectra are too simplistic to represent complex scenarios such as urban scenes with multiple sources in the soundscape and significant
ABSTRACT A methodology based on a combination of commercial software tools is developed for rendering complex acoustic scenes in real time. The methodology aims to bridge the gap between real time acoustic rendering algorithms which lack important physics for the exterior urban environment and more rigorous but computationally expensive geometric or wave-based acoustics software by incorporating pre-computed results into a real time framework. The methodology is developed by surveying the best in class commercial software, outlining a general means for accommodating results from each, and identifying areas where supplemental capability is required. This approach yields a real time solution with improved accuracy. Strengths and limitations in current commercial technologies are identified and summarized
The influence of moisture adsorption, prior braking, and deceleration rate on the low-speed braking noise has been investigated, using copper-free disc pads on a passenger car. With increasing moisture adsorption time, decreasing severity of prior braking or increasing deceleration rate, the noise sound level increases for the air-borne exterior noise as well as for the structure-borne interior noise. The near-end stop noise and the zero-speed start-to-move noise show a good correlation. Also, a good correlation is found between the noise measured on a noise dynamometer and on a vehicle for the air-borne noise. All the variables need to be precisely controlled to achieve repeatable and reliable results for dynamometer and vehicle braking groan noise tests. It appears that the zero-speed start-to-move vehicle interior noise is caused by the pre-slip vibration of the brake: further research is needed
To meet vehicle interior noise targets and expectations, components including those related to electric vehicles (EVs) can effectively be treated at the source with an encapsulation approach, preventing acoustic and vibration sources from propagating through multiple paths into the vehicle interior. Encapsulation can be especially useful when dealing with tonal noise sources in EVs which are common for electrical components. These treatments involve materials that block noise and vibration at its source but add weight and cost to vehicles – optimization and ensuring the material used is minimized but efficient in reducing noise everywhere where it is applied is critically important. Testing is important to confirm source levels and verify performance of some proposed configurations, but ideal encapsulation treatments are complex and cannot be efficiently achieved by trial-and-error testing. Simulation is a key supporting tool to guide location, thickness, and properties of
Test procedures are described for measuring noise at specific receiver locations (passenger and cargo doors, and servicing positions) and for conducting general noise surveys around aircraft. Procedures are also described for measuring noise level at source locations to facilitate the understanding and interpretation of the data. Requirements are identified with respect to instrumentation; acoustic and atmospheric environment; data acquisition, reduction and presentation, and such other information as is needed for reporting the results. This document makes no provision for predicting APU or component noise from basic engine characteristics or design parameters, nor for measuring noise of more than one aircraft operating at the same time. No attempt is made to suggest acceptable levels of noise or suitable subjective criteria for judging acceptability. ICAO Annex 16 Volume I Attachment C provides guidance on recommended maximum noise levels
This SAE Recommended Practice establishes the test procedure, environment, and instrumentation to be used for measuring the exterior exhaust sound level for passenger cars, multipurpose vehicles, and light trucks under stationary conditions providing a continuous measure of exhaust system or simulated exhaust sound level over a range of engine speeds or simulated engine speeds. This document applies only to road vehicles equipped with an internal combustion engine or with an external sound system. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. It is within the scope of this document to measure the stationary A-weighted sound pressure level during: Measurements at the manufacturing stage Measurements at official testing stations Measurements at roadside testing It does neither specify a method to check the exhaust sound pressure level when the engine is operated at
This SAE Standard is equivalent to ISO Standard 362 - 1997 except for the differences detailed in Appendix A, and includes the modifications adopted by WP 29 in ECE R51 Revision 1 and EEC 92/97 and EEC 96/20. This document specifies an engineering method for measuring the noise emitted by accelerating highway vehicles of all types (except motorcycles) in intermediate gears with full utilization of the available engine power. The method is designed to meet the requirements of simplicity and reproducibility of results under realistic vehicle operating conditions. Measurements relate to operating conditions of the vehicle which give the highest noise level consistent with urban driving and which lead to reproducible noise emissions. Therefore, an acceleration test at full throttle from a stated engine or vehicle speed is specified. The test method calls for an acoustical environment which can only be obtained in an extensive open space. Such conditions can usually be provided for: a
Numerical methodologies for aeroacoustic analyses are increasingly crucial for car manufacturers to optimize the effectiveness of vehicle development. In the present work, a hybrid numerical tool based on the combination of a delayed detached-eddy simulation and a finite element model, which relies on the Lighthill’s acoustic analogy and the acoustic perturbation equations, is presented. The computational aeroacoustics is performed by the software OpenFOAM and Actran, concerning respectively the CFD and the FEM. The aeroacoustic behavior of the SUV Lamborghini Urus at a cruising speed of 140 km/h has been investigated. The main aerodynamic noise phenomena occurring in the side mirror region in a frequency range up to 5 kHz are discussed. The numerical simulations have been verified against the measurements performed in the aeroacoustic wind tunnel of the University of Stuttgart, operated by FKFS. The predicted exterior noise propagation into the far field has been validated by
Pass-by noise measurement is mandatory for automotive manufacturers for conformity of production. With evolving of pass-by noise requirements (under 68 dB in 2024), all the stakeholders should be able to comply with this criterion. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are concerned and should deploy efforts to provide solutions for control of exterior noise. In this regard, simulations are preferable over measurement campaigns as they can provide fast feedback on passive exterior treatments for exterior noise control. In the particular case of Lightyear vehicles, the main contributors to pass-by noise are tires and in-wheel motors. Considering that, a contribution of each of these two sources of noise to pass-by noise will be described. Tire noise sources and motor noise sources will be replaced by simple monopole sources. The best monopole source location for both tires and motors is discussed. Actran vibro-acoustic Finite Element
The character and level of noise in a vehicle has changed significantly from the 1970s to today. In the 1970s the challenge was to permit communication from the front seat to the rear at highway speeds. In the last decade, the challenge has grown to provide a vehicle that provides the right "type" of sound while isolating the occupants from disturbing exterior noise. This may involve adding engine noise simulation and sculpting the interior sound to meet customer expectations. More recently, the challenge has been to modify noise controls for extreme light weighting exercises and electric vehicles. In addition, electric vehicles present a different sound environment and the challenge of determining what an EV should sound like. This paper will attempt to discuss these challenges and talk about the future of vehicle interior noise
Current and future EV’s contain significant amounts of complex electrical hardware, including rechargeable energy modules, control units, cooling systems and wiring situated inside the cabin usually below the carpet, seats or trunk trim and below the cabin floor. These items, whilst likely to have a direct impact on transmission loss, are increasingly difficult to evaluate via typical methods of computer-based simulation. In particular, the packaging space allocated for control units, which may require an air gap between the body in white and the carpet for aspects of heat stabilization can be difficult to model using the transfer matrix method. In the case of battery installations their high bulk mass doesn’t necessarily provide significant increases in transmission loss due to adjacent acoustic weaknesses and the inherent sensitivity of the floor system. This paper examines a selection of novel techniques, using sound Phonons, developed to predict both baseline transmission loss and
NVH is very important topic in development of a vehicle. Legislative requirements for driver ear level, the comparison to competitor vehicles in terms of noise and vibration as well as sound quality set very challenging targets. High noise at Driver Ear Level (DEL) and tactile vibrations of tractor is the major cause of exhaustion to the operator. With growing competition there is need for the tractor manufacturers to control noise and vibration levels. Recognizing the corrective measures to reduce the noise and vibration has a greater impact in increasing the efficiency of the product and operator comfort. Objective of this paper is to control vehicle level noise and vibrations using vehicle level structure modifications. It includes airborne and structure borne NVH study on a tractor by measuring sound pressure and vibration levels at vehicle level. Single cylinder engine was mounted on light weight structure to meet the power and torque requirements in the tractor. Also, there is no
This SAE Standard establishes the procedure for determining the operator duty cycle sound pressure level Lodc to which operators of powered recreational craft up to 24 m in length are exposed during typical operation as determined by marine engine duty cycle studies. This document describes the instrumentation, the required calibration procedures, the test site, the specifications for “standard craft”, the craft operating conditions, microphone positioning, test procedure, engine speeds for each of the Duty Cycle modes and the formula and table for calculating the Duty Cycle operator ear sound pressure level. This document is subject to change to keep pace with technical advances as well as other international standards and practices. Changes in this Revision: The sound pressure level measurements performed while applying this document are based on the Five-Mode Marine Engine Duty Cycle instead of a single engine speed. A calculation is required to obtain the Duty Cycle operator ear
The scope of this SAE Recommended Practice covers specialized internal combustion engine powered equipment used in support of aircraft operations. The equipment may be self-propelled, truck mounted, trailer mounted, skid mounted or stationary. It does not include construction equipment or equipment designed primarily for operation on highways or within factories or building areas. NOTE: Equivalent methodology is provided in (CEN) EN 1915-4, Aircraft ground support equipment - General requirements - Part 4: Noise measurement methods and reduction, to be used for measurements conforming to the EU Machinery Directive
NVH has gained importance in the field of earth moving equipment due to the demand of quieter machines and stringent in-cab as well as exterior noise emission norms. Several parts of the world have adopted strict legislation on noise emission by earth moving equipment, but many countries have not adopted any regulations till date. The aim of this study is to help governing bodies as well as machine manufacturers in adopting simple yet accurate testing method for compactor machine. The study consists of directivity analysis, noise source identification, noise source ranking and 4-point microphone position sound power evaluation method applied to compactors with wide range of engine power ratings. All the tests in 4-point method and directivity analysis were performed under stationary as well as dynamic conditions. Currently, several countries and vehicle manufacturers have adopted sound power evaluation of compactor exterior noise emission by 6-point method (as per ISO 6393 and ISO 6395
Pass-by/exterior noise of earth moving machines (EMM) and forestry machines is becoming a focus at early product development stages. ISO 6395 (2) or EC/2000/14 (1) standards defines exterior noise test procedure for EMM. However, these standards do not provide insights for diagnosing any noise issues which may arise. The analysis challenges are posed by the moving machine and acoustic sources with respect to the stationary hemisphere target microphone on the ground and changing operating condition of sources as function of time. There is need to develop a seamless methodology to identify acoustic sources, quantify respective source strengths and rank partial contributions from each source to the total target microphone response in order to overcome the aforementioned challenges. This paper demonstrates use of time and frequency domain Acoustic Source Quantification (ASQ) combined with time domain overall sound pressure level computation to mimic operational test conditions which
Noise and vibration measurements were conducted on eight light vehicles ranging from small compact passenger cars to a large sport utility vehicle on and off shoulder rumble strips of two different designs to assess the input to a vehicle operator when the vehicle departed from the travel lane. The first design was a more conventional design, consisting of cylindrical indentions ground into the pavement at regular 30 cm intervals, and a continuous sinusoidal profile with a peak-to-peak length of 36 cm. Triaxial vibration measurements were made at six locations, including the steering wheel and column, the seat cushion and track, and the front and rear spindles. Interior noise was measured at six locations, one at the operator’s outward ear and five at the front seat passenger (three in the fore/aft locations of the seat and at outboard and inboard ear locations). In addition to the in/on vehicle measurements, pass-by noise levels were made. The measurements were performed at 97 km/h
The automotive industry is shifting towards the development of hybrid electric and electric vehicles. These vehicles primarily use electric motors for propulsion and can be significantly quieter to pedestrians than traditional ICE (internal combustion engine) vehicles. The NFB (National Federation of the Blind) and others highlighted a concern with these quiet vehicles related to pedestrian safety and the inability to use historical sound signatures to detect a moving vehicle. To address this concern, NHTSA created FMVSS 141, which identifies minimum external sound requirements for hybrid and electric vehicles during stationary conditions and in motion up to 30kph. [1] OEMs are now required to implement Acoustic Vehicle Alerting Systems (AVAS) that use external speakers to generate additional noise to meet the regulation. These noises are intended to raise the exterior sound level of the vehicles, while still attempting to maintain a quiet, pleasant experience for the passengers in the
This SAE Information Report provides basic information about the issues surrounding the administration of stationary, infield sound testing of snowmobiles. The information provided herein is meant to enhance safety, improve the environment, and promote uniform testing
This SAE Standard establishes the test procedure, environment, and instrumentation for determining the sound levels of snowmobiles in the stationary test mode. This test method is intended to provide an accurate measurement of exhaust and other engine noise and may be used to evaluate new and in-use snowmobiles to determine compliance with noise control regulations. Sound level measurements obtained with this test method are not intended as an engineering determination of overall machine noise. For this purpose, the use of SAE J192 is recommended
This SAE Recommended Practice establishes the test procedure, environment, and instrumentation for determining the maximum exterior sound level of highway motor trucks and truck tractors over 4540 kg gross vehicle weight rating (GVWR) with governed engines under stationary vehicle conditions. The basic procedure involves a full throttle engine acceleration and a closed throttle deceleration with the engine inertia as the load
This SAE Standard establishes the instrumentation, test site, and test procedure for determining the maximum exterior sound level for snowmobiles
This SAE Standard establishes a uniform test procedure for determining the exterior operational sound level for snowmobiles
This SAE Standard establishes a uniform testing procedure and performance requirements for a snowmobile brake control systems
Current vehicle regulations demand for a challenging decrease in the overall exterior noise as a benefit for the health of citizens and road users. New limits have been implemented in UN R51.03 (based on ISO 362-1:2015) to reduce the emitted noise both at constant speed and in full load so as to cover most of the real urban driving conditions. In order to achieve those targets the carmakers have to refine the trim of their vehicles and an experimental approach can take place too late. This paper shows a method for the pass-by noise simulation exploiting the numerical transfer functions and a library of experimentally characterized sources with the aim to reduce the noise and find out a better tradeoff between costs and effectiveness of the modifications. Moreover a simple software tool for the treatment of the data and to ease the workflow has been created and used for the rank assessment of the different paths
Axial cooling fans are commonly used in electric vehicles to cool batteries with high heating load. One drawback of the cooling fans is the high aeroacoustic noise level resulting from the fan blades and the obstacles facing the airflow. To create a comfortable cabin environment in the vehicle, and to reduce exterior noise emission, a low-noise installation design of the axial fan is required. The purpose of the study is to investigate efficient computational aeroacoustics (CAA) simulation processes to assist the cooling-fan installation design. In this paper we report the current progress of the investigation, where the narrow-band components of the fan noise is focused on. Two methods are used to compute the noise source. In the first method the source is computed from the flow field obtained using the unsteady Reynolds-averaged Navier-Stokes equations (unsteady RANS, or URANS) model. In the second method, the azimuthal modes of the flow field obtained using the steady RANS with the
This SAE Standard is equivalent to ISO 362-1:2015 and specifies an engineering method for measuring the noise emitted by road vehicles of categories M and N under typical urban traffic conditions. It excludes vehicles of category L1, L2, L3, L4, and L5. The specifications are intended to reproduce the level of noise generated by the principal noise sources during normal driving in urban traffic. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. The test method requires an acoustical environment that is obtained only in an extensive open space. Such conditions are usually provided for during: Measurements of vehicles for regulatory certification and/or type approval. Measurements at the manufacturing stage. Measurements at official testing stations
In the highly competitive global automotive market and with the taste of customer becoming more refined, the need to develop high quality products and achieve product excellence in all areas to obtain market leadership is critical. Buzz, squeak and rattle (BSR) is the automotive industry term for the audible engineering challenges faced by all vehicle and component engineers. Minimizing BSR is of paramount importance when designing vehicle components and whole vehicle assemblies. Focus on BSR issues for an automobile interior component design have rapidly increased due to customer’s expectation for high quality vehicles. Also, due to advances in the reduction of vehicle interior and exterior noise, engine mounts have recently been brought to the forefront to meet the vehicle interior sound level targets. Engine mounts serve two principal functions in a vehicle, vibration isolation and engine support. The objective of this paper to experimentally analyze the impact of conventional
This SAE standard establishes the instrumentation, test site, and test procedure for determining the maximum exterior sound level for snowmobiles. Sound propagation is directly related to the ground cover and provides the largest variation to the measured result. A correction factor is introduced to improve year-round test repeatability of the results on grass surfaces by correcting their spectrum to be similar to snow-covered spectra. Measured sound pressure levels are also highly dependent on the degree of track slip present when performing the vehicle acceleration. Operators should attempt to limit track slip as much as possible while maintaining the requirements described in 5.1.1
The ability to assess noise transmitted through seals to cabin interiors early in the design process is very important for automotive manufacturers. When a seal design is inadequate, the noise transmitted can dominate the interior noise, making the wind noise performance of the vehicle unacceptable. This can cause launch delays, increasing costs and risking loss of sales. Designing seals using conventional experimental processes is challenging, since the location and strength of flow noise sources are not known when the seal design is planned. Making changes to the seal system after the tooling stage is expensive for manufacturers as tooling and redesign costs can be considerable. Deliberate overdesign by adding multiple layers of seals in a wide range of locations also can reduce profit by unnecessarily raising part and manufacturing costs. Consequently, there is a strong motivation to use reliable computational capabilities to predict interior noise transmitted through seals early in
Stiffener ribs are widely used to increase the stiffness of engine blocks, shifting the vibration modes to higher frequencies where excitation is weaker so that radiated noise can be reduced. The effect of different rib design parameters on the radiated noise emission of a diesel engine has been investigated considering its impact on block weight. A heavy-duty engine block was modeled using finite element method, multi-body dynamics approach was used to determine the excitation forces acting due to combustion pressure and inertias, and boundary element method was used to find the acoustic transfer vectors which give the relationship between engine surface velocities and sound pressure levels at predetermined microphone locations. Initially, the baseline analytical sound pressure level and surface velocity results for the engine without ribs were obtained. Two prototype engines, with and without stiffened ribs, were tested in an acoustic dynamometer in complete speed range. Then, the
Optimizing noise control treatments in the early design phase is crucial to meet new strict regulations for exterior vehicle noise. Contribution analysis of the different sources to the exterior acoustic performance plays an important role in prioritizing design changes. A method to predict Pass-by noise performance of a car, based on source-path-receiver approach, combining data coming from simulation and experimental campaigns, is presented along with its validation. With this method the effect of trim and sound package on exterior noise can be predicted and optimized
This SAE Standard is equivalent to ISO Standard 362 - 1997 except for the differences detailed in Appendix A, and includes the modifications adopted by WP 29 in ECE R51 Revision 1 and EEC 92/97 and EEC 96/20. This document specifies an engineering method for measuring the noise emitted by accelerating highway vehicles of all types (except motorcycles) in intermediate gears with full utilization of the available engine power. The method is designed to meet the requirements of simplicity and reproducibility of results under realistic vehicle operating conditions. Measurements relate to operating conditions of the vehicle which give the highest noise level consistent with urban driving and which lead to reproducible noise emissions. Therefore, an acceleration test at full throttle from a stated engine or vehicle speed is specified. The test method calls for an acoustical environment which can only be obtained in an extensive open space. Such conditions can usually be provided for: a
This SAE Recommended Practice establishes the procedure for measuring the maximum exterior sound level of recreational motorboats while being operated under a variety of operating conditions. It is intended as a guide toward standard practice and is subject to change to keep pace with experience and technical advances
Exterior turbulent flow is an important source of automobile cabin interior noise. The turbulent flow impacts the windows of the cabins to excite the structural vibration that emits the interior noise. Meanwhile, the exterior noise generated from the turbulent flow can also cause the window vibration and generate the interior noise. Side-view mirrors mounted upstream of the windows are one of the predominant body parts inducing the turbulent flow. In this paper, we investigate the interior noise caused by a generic side-view mirror. The interior noise propagates in a cuboid cavity with a rectangular glass window. The exterior flow and the exterior noise are computed using advanced CFD methods: compressible large eddy simulation, compressible detached eddy simulation (DES), incompressible DES, and incompressible DES coupled with an acoustic wave model. The last method is used to simulate the hydrodynamic and acoustic pressure separately. The pressure fluctuations of the flow and noise
Items per page:
50
1 – 50 of 252