sound quality & product perception...

EIS SQ Workshop rw300614, 1

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Sound Quality & Product Perception Workshop

Interactive Assessment of Vehicle Sound Quality: Target Setting and Jury Evaluation

[email protected]


Agenda

1. Fundamentals of Automotive Sound Quality

2. Auralisation of Vehicle Sounds

3. Target Setting & Jury Evaluation



1. Fundamentals of Automotive Sound Quality


The Range of Human Hearing140

120

100

80

60

40

20

0

-10

Sou

nd

Pre

ssu

re L

evel

(d

B)

200

20

2

0.2

2e-2

2e-3

2e-4

2e-5

Sou

nd

Pre

ssu

re (

Pasc

al)

0.02 0.05 0.1 0.2 0.5 1 2 5 10 20

Frequency (kHz)

Speech

Music

(From: Psychoacoustics Facts and Models by Zwicker and Fastl)

Threshold in quiet

C/D-class vehicle at 120 kph on smooth road


Perception: How you analyse what you hear

6 Key Factors which influence our Perception of Automotive Sound

Quality:

1. Classification

2. Loudness

3. Masking

4. Modulation

5. Spectrum Balance & Sharpness

6. Harmonic Patterns



2. Auralisation of Vehicle Sounds using an NVH Simulator

“Drive and Evaluate a virtual vehicle on a virtual road”


NVH Simulator: Building Blocks for Interactive Auralisation

Modelling the Sound Modelling Vehicle Performance

+


NVH Simulator: Hierarchical NVH Model

Road + Wind + Tyre

Total Engine

+ …

Total Vehicle Level ▼

Sound & VibrationSound & Vibration

Total VehicleTotal Vehicle

Intake Orifice

Exhaust Orifice

Structure Borne

Road Noise Tyre Noise Wind

Source Level ▼

Air Borne

Left Mount XYZRight Mount XYZFront Mount XYZRear Mount XYZ……….

ContributionsFloor PanelsFirewall PanelsRoof PanelsGlass PanelsClosures Panels

ContributionsTop SurfaceRear SurfaceRight SurfaceLeft Surface……….

Contributions

Measured/CAE Source Strength x ATF

Sealing TestsIn Wind Tunnel(Test A – Test B)

Measured/CAEPath Strength x Body TF

Measured/CAEVolume Velocity X VTF

Measured/CAESource Strength x ATF

Front GlassSide GlassRear GlassMirrors etcSeals

Contributions

Contribution Level ▲


Interactive Demonstration:

• Engine Harmonics: Interaction between orders

Fundamental Firing Frequency

Even Orders

Odd Orders

Half Orders

• Sound Tuning using Filters

Step 1: Masking Target: Aim = featureless spectrum

o Road V. Low freq. = Fundamental design

o Road 300Hz = Tyre Cavity

o Road 800 Hz = Tyre Tread + Airborne Paths

o Wind = Reduce by 3-4 dB

Step 2: Introducing Positive Character i.e. Engine

o Remove boom

– Notch: F = 257, Bw= 170, dB= -12

o Source Strengths & Resonances

– Notch: F=480, Bw=90, dB=+10 (Structural… Sframe)

– Notch: F=700, Bw=200, dB=+10 (Intake….Bark tube)

More Orders & Resonances = Increased “Character”



3. Target Setting and Jury Evaluation Example


Preference: What you like/dislike about what you hear

Car sounds can contain two types of characteristics:

• Good Agreement between listeners• Can be quantified using Sound Metrics

• Preference can be very individual• We need to ask people!

1. Those that are annoying.

o Continuous when cruising

– Discrete (boom, gear whine)

– Wind noise especially leakage

– Road noise hollowness

o Short duration events, e.g. squeak and rattles, which stand out above the background noise

2. Those that can create a positive emotional response or information feedback.

o Either from their sound character e.g. powerful car accelerating

o Or from their ability to convey the quality of a product e.g. door shut


Why is vehicle sound quality so important?

Transmission

Ancillaries Ventilation

Wind

Road/Tyre

Total Exhaust TailpipeEngine

Intake

BrandDNA

• InteriorComfort

o Annoyance

o Loudness

Feeling of Quality

Charactero Driver satisfaction

o Communication

• ExteriorCharacter

Soundscape

Pedestrian Warning


Jury Testing: Capturing Subjective Opinion about Sound Quality

• Jury testing = Structured evaluation by many assessors using

robust methods to quantify:

Subjective Opinion:

o Which sound is most …..? e.g. most powerful/most relaxing/most

expensive.…

o Which words were used to describe the sounds?

o Which SQ features in a sound are most positive/negative ...?

o Which sound is most appropriate? e.g. EV warning sounds

Context:

o How/where was the car driven?

o What is the assessors driving style?

o How important is sound to the assessor?

Objective Analysis:

o Which metric best represents the SQ characteristics?

• Sounds Measured Modified Predicted

• People NVH experts Managers & Decision Makers Real Customers

• Context On-road Sound playback In-Room Using NVH Simulator

• Method Free Rating (Scaling) Semantic Differential Paired Comparison …..

• Sounds Measured Modified Predicted

• People NVH experts Managers & Decision Makers Real Customers

• Context On-road Sound playback In-Room Using NVH Simulator

• Method Free Rating (Scaling) Semantic Differential Paired Comparison …..

Jury Evaluations are used to guide the decision making process


Jury Evaluation: Overview of Common Methods

Rating

2-D Semantic Space

Powerful

Ref

ined

Semantic

4

5

6

7

8

9

Pleasant

Luxurious

Comfortable

Powerful

Sporty

Aggressive

Exciting

Fun

Spirited

Effortless

Quiet

Refined

4

5

6

7

8

9

Pleasant

Luxurious

Comfortable

Powerful

Sporty

Aggressive

Exciting

Fun

Spirited

Effortless

Quiet

Refined

Semantic Profile

Paired Comparison

Merit Scores

Car

Mer

its


Target Setting Example: Case Study – B Segment Vehicle Concept

• Summary of project1. Evaluate the Sound Quality of

the current vehicle relative to competitor

2. Use the NVH Simulator to create vehicle targets based on a current vehicle

3. Drive, evaluate and choose best option(s) in the NVH Simulator

4. Confirm the final target sound on-road

5. Cascade the targets to components/sub-systems

6. Engineer the targets

Marketing Aim: “Sporty sound without being overly intrusive”


Target Sound: Evaluation Results

• Preferred target options identified using NVH Simulator Jury Evaluation

• Final Concept Proposal sound was presented using the On-Road Simulatorat Target confirmation drive events.

• Event was attended by all key programme management and decision makers.

• All attendees liked the sound and thought it was completely right for the product.

Target sound demonstrated and agreed at the concept stage of the programme


Conclusions

1. Fundamentals of Automotive Sound Quality It is important to understand a few basic psychoacoustic principles and use them in the sound

design process

2. Auralisation of Vehicle Sounds using the NVH Simulator Evaluate in the correct Context i.e. while driving

Interactivity is important i.e. change load, speed, gear, road surface….

Listen, Visualise & Modify sounds in real-time….”What-if?”

3. Target Setting & Jury Evaluation Capture the subjective preference of non-experts (decision makers, real customers) as well as

NVH experts

Need to use robust but simple and enjoyable jury evaluation methods

and finally ....


Sound A

Sound B

..so you think you understand Sound Quality?

Which of these sounds is more powerful?



Sound Quality & Product Perception Workshop

Interactive Assessment of Vehicle Sound Quality: Target Setting and Jury Evaluation

Roger Williams

sound quality & product perception...

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