Journée vibroacoustique SFA/GSO

Vibro-acoustiques appliquée

dans l’industrie automobile

Laurent Gagliardini DRD/DAPF/ACV

What is NVH?

Noise, Vibration, and Harshness (NVH), or in French “ACoustique et Vibrations”

(ACV) is the study and modification of the noise and vibration characteristics of

vehicles in order to achieve a given performance target:

NVH is one component of the customer overall comfort feeling

The NVH targets are provided by the marketing department, in accordance with the

project management since it is highly cost related

NVH includes

Physical matters (structural dynamics, fluid mechanics and acoustics)

Physiology (hearing)

Social psychology (Sound quality, Annoyance)

Vehicle NVH : physical analysis

Included

Road, Engine and Appliances vibrations (5 Hz – 100 Hz)

Aerodynamic, Road, Engine and Appliances noise (30 Hz – 10 kHz)

Squeak and rattle

Excluded

Vehicle dynamics (< 5Hz)

Road-noise

Aerodynamic noise

Powertrain Noise

Appliance noise(HVAC …)

Powertrain noise

Rotating machinery: periodic forces (torque and inertial forces)

Combustion noise: shocks

Mechanism noise: gears noise, belts vibrations

Function of rpm and torque

Test bench

Vehicle on Rollers, Powertrain in an anechoic dynamometer

Main associated vehicle attributes

Idling noise, booming noise, combustion noise, gear and belt whines

60

0

20

40

Pression (dBA)

0 25001000 2000

Fréquence (Hz)

moteur plancher - 2e - 3000tr - FC - série - 110 - ref - Global

0 500 1000 1500 2000 2500 Frequency Hz

20 d

B

Engine 2nd harmonic (H2)

Tire-road interaction: random forces

Isolated obstacles: shocks

Corrugated road : quasi-periodic excitation

Function of speed and road surface

Roughness spectrum ~1/ω2.5

Test bench

Tracks, coarse surface rollers, hydro shakers (4 posters)

Main vehicle attributes

Impact noise and vibration, Road-noise, Tire-noise…

Road noise and vibrations

Aerodynamic noise

Turbulence generated by the vehicle shape and exterior equipment (antenna, side mirrors, wipers)

Turbulence in the HVAC system : fan, air outlet

Function of vehicle speed (V5) and wind direction

Test bench

Acoustic wind tunnel

Associated vehicle attributes

HVAC noise, wind noise

-10

0

10

20

30

40

50

10 100 1000 10000

Frequency [Hz]

dB(A

)

View of main aerodynamic noise sources

(Source modelling from CFD)

Vehicle attributes overview:

frequency range and transmission path

Road

excitation

Powertrain

excitation

Frequency [Hz]

Aerodynamic and

environnemental

excitation

10 00020 200 500050 500 20001000

Road noise 20-500 Hz

Booming 20-300 Hz

MF level 250-1000 Hz

HF level 400 Hz - 10 kHz

Impact N&V 20-200 Hz

Tire noise 400-4000 Hz

Exterior noise insulation 400 Hz - 10 kHz

Aerodynamic noise 50 Hz - 10 kHz

100

Systems N&V 50 Hz - 10 kHzEquipment

excitation

Air-Borne Structure-Borne

Parts manufacturing

Vehicle Level

Sub-system Level

Component Level

Requirem

ents

Design In

tegration

Assessment

Vehicle systems engineering

Marketing

Vehicle attributes Production vehicle

Sales

Customer

Suspension

Powertrain

Tire/Wheel

Elastic

mounts

Vehicle decomposition regarding NVH issues

Body in White

Trimmed Body

PSA NVH department (ACV) tasks

ACV is in charge of:

Vehicle and sub-systems NVH requirements

Providing expertise for vehicle and sub-system design

Assessment of vehicle/sub-systems performances

For all vehicle and sub-systems attributes related to noise

and vibration comfort (5 Hz-20 kHz)

Excluded : squeak and rattle, audio equipment

Included : sound quality

ACV is also in charge of pass-by noise homologation

Project schedule and NVH operations

Advanced devpt

Vehicle

requirements

Architecture

definition

Development

Subsystems

requirements

Parts

definitions

Tooling

definitions

Manufacturing

First

prototype

In-line

production

SOP

Design phase

CAD ���� FE mesh ���� simulation

Modification Target checking

Concept phase

Sketches � Functional modelling

Architecture Project balance

Physical understanding

Benchmarking

Feedback

Academic

studies

Assessment phase

Experimentation���� Trouble shooting

Prject tuning

Forecast capabilities

Analysis capabilities

Performance metrics Detailed modelling

Sensitivity analysis

Efficient assessment

Process control

Products

technology

Experimental

tools

Hybridization

Project schedule and NVH operations

Advanced devpt

Vehicle

requirements

Architecture

definition

Development

Subsystems

requirements

Parts

definitions

Tooling

definitions

Manufacturing

First

prototype

In-line

production

SOP

Design phase

CAD ���� FE mesh ���� simulation

Modification Target checking

Concept phase

Sketches � Functional modelling

Architecture Project balance

Physical understanding

Benchmarking

Feedback

Academic

studies

Assessment phase

Experimentation���� Trouble shooting

Project tuning

Forecast capabilities

Analysis capabilities

Performance metrics Detailed modelling

Sensitivity analysis

+ Structural complexity

+ Uncertainties

+ Multiple operating conditions

+ Trade-off with others

Efficient assessment

Process control

Products

technology

Experimental

tools

Hybridization

Overview of typical vibroacoustic behaviour

Low frequencies

Isolated frequencies with high response � modal behaviour � FEA

Strong correlation between distant points responses

High frequencies

Smooth frequency response � statistical behaviour � Energy methods

Response is locally homogeneous (diffuse field)

Structural/

acoustic

response

Frequency

Isolated modal

resonances

Overlapping modal

resonances

Diffuse response

(statistical modal

behaviour)

LF MF HF

Frequency range decomposition for NVH studies

Based on physical behaviour …

Ultra Low frequency: Rigid body motion, non-linearity

Low frequencies : modal behaviour

Mid frequencies : mix of modal and statistic behaviour

High frequencies : Statistic behaviour, energy methods

… or based on human hearing

Bass (<250 Hz)

Medium (250-1600 Hz)

Treble (> 1600 Hz)

ULF

LF

MF

HF

Main Vehicle Subsystems

physical behaviour versus frequency

Body

Powertrain

Suspension

ULF LF MF HF

Log f40 Hz20 Hz 400 Hz200 Hz 4 kHz2 kHz800 Hz80 Hz

Bass Medium Treble

First elastic mode

Body

Powertrain

Suspension

ULF LF MF HF

Log f40 Hz20 Hz 400 Hz200 Hz 4 kHz2 kHz800 Hz80 Hz

Multi-body (MBS)

Finite ElementAnalysis(FEA)

Numerical techniques versus frequency

Energy methods(SEA)

Bass Medium Treble

Mid-Low Frequencies Vibroacoustic

Numerical Tools

Interior noise (vehicle)

Pre-post : Virtual.lab (LMS)

• Included : FRF assembly, Forced response (multiple loads, random

loads)

Solver: NASTRAN (MSC) / AMLS (CDH)

Exterior noise (vehicle) + Radiation (Powertrain)

Pre-post : Virtual.lab (LMS)

Solver: SONATE (IMACS)

Ducts acoustics

Pre-post: IMS/ANSA

Solver concept: GT-Power

Solver detailed: ACTRAN (FFT)

Tire / Brake squeal

Pre-post: IMS/ANSA

Solver: ABAQUS (DS)

High Frequencies Vibroacoustic

Numerical Tools

Vehicle insulation (airborne)

VAOne (ESI)

SEA + (InterAC)

Interior propagation

Pre-post: Virtual.lab

Solver: ICARE (CSTB)

Engine bay propagation

VAOne (ESI)

HVAC noise

AMESIM (LMS)

Aeroacoustics

Fluent (Ansys)

Powerflow/Poweracoustics (Exa Corp)

Test benches and tracks

3 full anechoic powertrain dyno

1 quiet 4 WD roller bench

6 standard semi-anechoic 2WD roller benches

1 large semi-anechoic 2WD roller benches

2 sub-systems semi-anechoic 2WD roller benches

2 semi-anechoic rooms

3 vibrations platforms

3 couples of reverberant rooms

2 small cabins

1 alpha Cabin

….

2 proving grounds

2 Pass-by tracks

1 (shared) acoustic wind tunnel (S2A/ St Cry l’Ecole)

Measurement systems

General purpose measurements

Test.lab (LMS)

Binaural recording, processing and listening

Artemis (Head Acoustics)

Sound insulation (small and large cabins, Alpha Cabin)

Pulse (B&K)

Powertrain antenna

In-house (+ MicrodB)

Wind tunnel antenna

Specific S2A (SD)

Vehicle interior antenna

Spherical antenna (MicrodB)

Future of NVH (2020-2025) for passenger vehicles

(conclusions of SIA WG)

Today situation

Lot of improvement in the past 20 years

Acoustic comfort takes part to the vehicle overall performance

evaluation

Silent driving is not any more related only to luxury cars

Tomorrow constrains

Environmental concerns

• CO2 and related fuel consumption

• Pollutant post treatment

• Noise pollution (Better City – Better Life)

Global market:

• low-cost to premium cars for every market

• Specific performance “trade-offs” for specific markets

Cost concerns

• optimized industrial process from the design to the manufacturing

• Within the extended company : OEM and suppliers

Future challenges

Be able to maintain high NVH performance, considering

High mass reduction to decrease CO2 emissions

• Up to 40% mass reduction for a given car size

• New vehicle architectures, using lightweight material

Evolution of powertrains systems

• Thermal engine remains the main power source, with improved performance

and downsizing

• Hybridization (light to mild to full) generalized

• Energy restoring

ZEV issues

• Security issues related to noise (interior and exterior, safety of pedestrians)

� new regulation

• Management of secondary sources (quality issues)

• Battery cooling

Recommendations

Training and knowledge sharing

With universities

Between OEMs and suppliers

Standardization and data sharing

Standardize measurements

Standardize NVH components

Adaptation of methodologies to new coming technologies

Test benches

Modelling

NVH improvement