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
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Agenda
1. Fundamentals of Automotive Sound Quality
2. Auralisation of Vehicle Sounds
3. Target Setting & Jury Evaluation
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1. Fundamentals of Automotive Sound Quality
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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
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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
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2. Auralisation of Vehicle Sounds using an NVH Simulator
“Drive and Evaluate a virtual vehicle on a virtual road”
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NVH Simulator: Building Blocks for Interactive Auralisation
Modelling the Sound Modelling Vehicle Performance
+
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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 ▲
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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 ▲
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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”
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3. Target Setting and Jury Evaluation Example
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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
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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
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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
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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
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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”
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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
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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 ....
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Sound A
Sound B
..so you think you understand Sound Quality?
Which of these sounds is more powerful?