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Exterior Noise Perception of BEV

Kathrin Dudenhöffer, Sven Staudt Universität Duisburg Essen

Bonn, 5th December 2011

Gianotti

Stamp

Agenda

1. Concept of the study

2. Interviews with blind people

3. Acoustic measurements, subjective

perception, and critical distance

4. Possible solutions

5th December 2011 CAR Universität Duisburg-Essen 2

Concept of the study

Three runs of the study in Juli 2010, November 2010, and April 2011

3

Acoustic measurements

At the test location and on the vehicle

measurement site of Ford in Cologne-

Merkenich (according to ISO 362,

7.5 m distance)

Experimental study, written

questionnaires (questionnaires were

developed together with blind people)

Group discussions with blind and visually

impaired persons (October 2010, April 2011)

5th December 2011 CAR Universität Duisburg-Essen

Interviews with blind people

Subjective perception Critical distance

Time to arrival measures via Buzzer-System

Research Problem

Group discussion I with members of an German organization of blinds, October 2010

Focus: Necessity of artificial sounds for quiet cars

Results:

• Fear of being limited in mobility and of being excluded from social life due to the

diffusion of electric cars;

• Demand of organizations to fit quiet electric cars with artificial sounds;

• Necessity of being able to follow the drive of a vehicle via its soundscape;

• A common, traditional engine sound is better predictable than uncommon, new

sounds (like Nissan Leaf or Chevrolet Volt);

• Special problem for blinds at crossings without signals, because standing cars (BEV,

HEV or ICE with automatic start/stop) cannot be heard.

CAR Universität Duisburg-Essen 4 5th December 2011

Research Background

5

Concept HEV (in electric mode) vs. ICE BEV vs. ICE

Subjective perception Field study

JASIC 2009 (only for warning system)

Subjective perception Laboratory study

NHTSA 2010 JASIC 2009 (HEV, CNG) Rosenblum 2008

Acoustic measurements Field study

---

Acoustic measurements Laboratory study

NHTSA 2010 JASIC 2009 (HEV, CNG) Rosenblum 2008 Wiener et al. 2006

Focus of research


Test vehicles

6

Ford Transit Peugeot Partner

Smart Fortwo e.d.

Comparisons of BEV with one or two identical ICE (Diesel and Petrol) (only BEV shown)

Mega e-City German-E-Cars Stromos


Average sound levels at measurement site

CAR Universität Duisburg-Essen 7

65

65

65

62,5

61,5

60,5

60

59

58

57,5

57

Peugeot Partner Benzin

Ford Transit Diesel

Ford Transit BEV

Smart Fortwo Diesel

Smart Fortwo Benzin

Ford Fiesta Benzin

Peugeot Partner BEV

Opel Agila Benzin

Smart Fortwo BEV

Mega e-City BEV

German-E-Cars Stromos BEV

Sound level in dB(A) Vehicle Test condition: Constant drive

German-E-Cars Stromos BEV 30 km/h

Mega E-City BEV 30 km/h

Smart Fortwo BEV 30 km/h

Opel Agila Petrol 30 km/h (2nd gear)

Peugeot Partner BEV 40 km/h

Ford Fiesta Petrol 30 km/h

Smart Fortwo Petrol 30 km/h (2nd gear)

Smart Fortwo Diesel 30 km/h (2nd gear)

Ford Transit BEV 40 km/h

Ford Transit Diesel 40 km/h (3rd gear)

Peugeot Partner Petrol 40 km/h (2nd gear)

Quiet BEVs

Quiet ICE

Noise Map – CRS Fiesta Petrol/e-City


7060504030

80

75

70

65

60

55

50

V_PP [km/h]

SPL_

avg

[dBA

]

E-City BEV - CRS - 1Fiesta ICE - CRS - 2Fiesta ICE - CRS - 3

Veh - Test - Gear

CRS - SPL_avg vs V_PP

Standing and Slowly Driving Cars

• While standing Stromos ist not perceivable.

• At a speed of 10 km/h (constant drive, equals to walking speed) Stromos is quieter

than Agila. Stopping distance is 4 m (less dangerous).

• From a speed of 20 km/h on Stromos and Agila converge.

• While accelerating the Stromos is quieter than Agila.

Average sound levels at test location:

*) Difference of one decibel perceivable, difference of three decibel equates to a 1,23-fold loudness, difference

of 10 decibel equates to double loudness.


Speed, constant drive Stromos (BEV) Agila (ICE) Difference*

10 km/h 49 dB(A) 52,5 dB(A) (1st gear) 3,5 dB

20 km/h 53,5 dB(A) 54,5 dB(A) (2nd gear) 1 dB

Experimental Study

Sample: 240 Participants

• 40% female, 58% male, 2% n.a.

• Middle age: 35 years, range: 5 – 94 years

• Visually impaired or blind: 15% (36 persons)

• Hearing impaired: 14%

• Driver licence: 51%

• Experience with BEV: 6%, Experience with HEV: 8%

Task: Cross street after vehicle has passed!*

*) Help offered for blind persons at crossing and for answering the

questionnaires.


Extreme Rather Neither nor Rather Extreme

-2 -1 0 1 2

quiet loud

faint powerful

smooth tight

dull metallic²

ordinary unique

damped booming³

soft hard

deep high

Sound Perception Transit

11

Semantic Differential¹

CAR Universität Duisburg-Essen

1) Means, 2) difference significant, 3) difference not significant. Ford Transit Diesel Ford Transit BEV


-2 -1 0 1 2

quiet loud²

faint powerful

smooth tight³

dull metallic

ordinary unique

damped booming

soft hard

deep high

Sound Perception Smart

12



Smart Fortwo Diesel Smart Fortwo Benzin Smart Fortwo BEV

1) Means, 2) difference significant, 3) difference not significant.


-2 -1 0 1 2

quiet loud²

faint powerful

smooth tight

dull metallic³

ordinary unique

damped booming

soft hard

deep high

Sound Perception Fiesta/e-City

13



1) Means, 2) difference significant, 3) difference not significant. Ford Fiesta Petrol Mega E-City


-2 -1 0 1 2

quiet loud³

faint powerful

smooth tight

dull metallic

ordinary unique

damped booming

soft hard

deep high

Sound Perception Agila/Stromos

14



1) Means, 2) difference significant, 3) difference not significant. Opel Agila Petrol German E-Cars Stromos

Subjective Perception: Emergence

15

3%

13% 14%

3% 5%

13%


Fahrzeug tauchte unerwartet auf unsicher/weiß nicht

27%

6%

17%

Difference significant


Vehicle appeared unexpectedly Unsure/I don‘t know

Smart Diesel Smart Petrol Smart BEV

Subjective Perception: Emergence

16 5th December 2011 CAR Universität Duisburg-Essen

11%

15%

8%

17%

7%

9%

4% 5%

Agila Stromos Fiesta e-City

Fahrzeug tauchte unerwartet auf unsicher/weiß nicht

Unterschied nicht signifikant

18%

24%

12%

22%

Vehicle appeared unexpectedly Unsure/I don‘t know

Difference not significant Difference not significant

Petrol Agila Petrol Stromos Fiesta Petrol

4% 6%

11%

Smart Fortwo Diesel

Smart Fortwo Benzin

Smart Fortwo BEV

In wie vielen Fällen wird in dieser Situation ein Fußgänger verletzt?

8%

14%

Ford Transit ICE Ford Transit BEV

Subjective Perception: Probability of accident

17

Difference significant Difference significant


In how many cases will a pedestian be hurt?

Petrol Smart Diesel Smart Petrol Smart BEV Transit Diesel Transit BEV

Subjective Perception: Probability of accident


16% 16%

12%

16%


In wie vielen Fällen wird in dieser Situation ein Fußgänger verletzt?

In how many cases will a pedestian be hurt?


Agila Petrol Fiesta Petrol

19

Subjective Perception: Fear of accident

0%

7% 7%



Have you been feared of an accident? – Yes.


Smart Diesel Smart Petrol Smart BEV

10%

9%

7%

11%


Subjective Perception: Fear of accident


Have you been feared of an accident? – Yes.


Agila Petrol Fiesta Petrol

Objective perception


At a speed of 30 km/h: breaking distance: 9 m

+ reacting distance: 9 m = total stopping distance: 18 m

8%

20%

Fiesta e-City

Critical Distance

Vehicle perception too late

(vehicle distance < stopping distance)


Fiesta Petrol

Objective perception


Differences not significant

15% 16%

4% 6%

Agila Stromos

kritische Distanz missed detection Vehicle perception

within stopping distance

Vehicle perception after

passing critical distance

Agila Petrol

Agila/Stromos at lower speeds

Group discussion II with participants of the study subsequent to the 3rd run, April 2011

Focus: Evaluation of Stromos/Agila Petrol in different driving modes at lower speeds

Results:

• Stromos (BEV) is quiet, but perceivable at 20km/h constant drive (no combustion

noise, but tire noise);

• At 10 km/h constant drive Stromos is too quiet and the situation is more dangerous

(no combustion noise, less tire noise);

• The perception of the identical vehicle Agila Petrol is similar to the BEV (less

combustion noise compared to other ICE);

• Parallel parking at the roadside is hardly perceivable and therefore dangerous for

Stromos and Agila Petrol;

• In the situation “stop at cross-walk” decelerating of Stromos is quiet, but

perceivable, while accelerating is too quiet to be heard; Agila is perceivable.


Discussion of Possible Solutions

Focus: Solution of the problem: Sound or warning system


Group I (organized and more conventional

thinking people)

Group II (highly technophile and more

open minded people)

Sound as single acceptable solution • Traditional engine sound preferred • Sound should correspond to speed • Acoustical tracking of moving vehicles • Demografic change has to be considered

(increasing number of hearing impaired people)

Problems • Acustic impulse overload • All quiet vehicles are dangerous (also bicycles)

Resistance against technic-based warning system • Not-technophiles excluded

Several soultions conceivable • Additional sounds for quiet cars in general

necessary (especially for lower speeds and while standing)

• Acoustical signal at the car helps, but does not prevent accidents

• Specific haptic warning via white cane, if vehicle approaches

• Additional warning for driver of approaching car via transmitter in the white cane

• Problem also relevant for children or hearing impaired persons

The far side of additional sounds

• Traffic noise can have heavy consequences like risks of sleep disorder, lack of

concentration or damage to hearing;

• People who are constantly exposed to traffic noise of 65 decibel have a higher risk

of infarction;

• Noise results in detachment of stress hormones and in the long run this causes

body overstraining;

• Noise abatement is highly expensive

(silent asphalt, quiet goods trains,

noise barriers);

• The diffusion of electric cars would

implicate noise reduction as a free add-on.



In the short run:

Natural engine sound for all quiet vehicles in general.

In the long run:

Electronic assistant system, which is able to warn the affected person

(haptically or acustically) and the driver of the vehicle at the same time.

Possible solution

Electronic Warning System

Backup


Noise Map – ROL Fiesta Petrol/E-City


7060504030

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75

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65

60

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V_PP [km/h]

SPL_

avg

[dBA

]

E-City BEV - ROL - NFiesta ICE - ROL - N

Veh - Test - Gear

ROL - SPL_avg vs V_PP

Noise Map – DBY Fiesta Petrol/E-City


7060504030

80

75

70

65

60

55

50

V_PP [km/h]

SPL_

avg

[dBA

]

E-City BEV - DBY - 1Fiesta ICE - DBY - 2Fiesta ICE - DBY - 3

Veh - Test - Gear

DBY - SPL_avg vs V_PP

Acoustic measures Transit - cruise

31

6050403020100

75

70

65

60

55

50

v_avg

spl_

avg

Transit - BEV - crs - 0Transit - ICE - crs - 1Transit - ICE - crs - 2Transit - ICE - crs - 3Transit - ICE - crs - 4

code

TRANSIT - CRS - Rolling with engine noise

code BEV – 0 ICE – 1 ICE – 2 ICE – 3 ICE – 4


Acoustic measures Transit - roll

32

605040302010

75

70

65

60

55

50

v_avg

spl_

avg

Partner BEV - cstPartner ICE - cstTransit - BEV - cstTransit - ICE - cst

code

CST - Free rolling w/o engine noise

6 dB


Experiment Location

33 5th December 2011 CAR Universität Duisburg-Essen

Subjective Safety of Blinds

34

Extremely safe Rather safe Neither nor Rather

unsafe Extremely

unsafe

In general

Rain and wet conditions

Strong wind

Snow


Blind and visually impaired persons

Relevance of Vehicle Exterior Noise

35

Extremly unimportant

Rather unimportant Neither nor Rather

important Extremely important

Sound of a standing vehicle

Sound of a slowly driving vehicle

Sound of a fast driving vehcile

Not visually impaired persons Blind and visually impaired persons


Differences significant

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