Study

“Perception and evaluation of Vehicle exterior noise by pedestrian

in different traffic situations and different operating conditions”

Date Nov. 2014

Vehicle exterior noise different traffic situations /operating conditions

Based on the performance measurement of ICEV- noise, possible perception deficits of EV-/ HEV-noise should be shown

1. Pre Coming vehicleVehicles:

14 ICEV (8 Petrol/6 Diesel)4 EV2 HEV1 EV Synthetic Sound

at 3 traffic-situations:

Vehicle exterior noise different traffic situations

2. Approaching vehicle parking lot

3. Slowing vehicle Cross-walk

49 dB(A)

Very Quiet Quiet

52 dB(A)

62 dB(A)

Very NoisyNoisy

60 dB(A)

/ operating conditions

Starting Speed: 0 km/hICEVEVHEVSynthetic

Vehicle recognized

Position Dummy- Head Microphon

Backround Noise:Very Quiet / Quiet / Loud / Very Loud

Recognition time

1. Pre Coming vehicle

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• Backround Noise: Very Quiet (49 dB(A))

EV / HEV Speed at micro 30 km/hICEV Speed at micro 50 km/h EV Sound

1. Pre Coming vehicle

• Backround Noise: Noisy (60 dB(A))

EV / HEV Speed at micro 30 km/h

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EV SoundICEV Speed at micro 50 km/h

1. Pre Coming vehicle

Backround : Quiet and Noisy

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Biggest differences of Recognition-time

between Quiet (52 dB(A) and Noisy (60 dB(A)) !

Only this 2 cases will shown

No Corelation between Recognition time and

Recognition SPL !

Examples … Reco

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Recognition SPL

1. Pre Coming vehicle

Audi Q5 (HEV no AVAS) 30 km/h at microRecognition time: 4,1 sec.Backround overall SPL: 57 dB(A)Vehicle overall SPL: 52,4 dB(A)1/3 Oct.: No level higher than Backround !

Mits. IMev (EV no AVAS) 30 km/h at microRecognition time: 4,2 sec.Backround overall SPL: 57 dB(A)Vehicle overall SPL: 61,5 dB(A)1/3 Oct.: above 200 Hz each level higher than Backround Noise !

Recognition time: 1,4 sec.Backround overall SPL: 57 dB(A)Vehicle overall SPL: 52,7 dB(A)1/3 Oct.: Between 100 & 500 Hz levels higher than Backround Noise!

Matiz (EV with AVAS) 30 km/h at micro

1. Pre Coming vehicle

2. Approaching vehicle

1. ICEV starting from idle (Diesel) „V-LL“2. ICEV after engine start (Diesel) „V-MS“3. EV without Sound „E-FZ“

5 different sounds:

4. EV Synth. Starting- & Idling-Sound „Syn-LL“

5. EV Synth. Starting- & NO Iddling-Sound „Syn“

„Idling“

Sound 4 „Syn LL“ Sound 5 „Syn“

Vehicle exterior noise …Re

cogn

ition

tim

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Overall AverageWithout distraction (backraound quiet)Without distraction (backraound noisy)With distraction (backraound quiet)With distraction (backraound noisy)

NoiseIdling Diesel

Starting Diesel

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Overall AverageNot Visually impairedVisually impaired

Results: TimeOnly Small difference between ICE (0,82 s / 1,02 s) and Syn/Syn-LL (1,3 s)

Results : Distance

ICEV

EV (no Sound)

Conclusion: - Synthetic sound is needed- Stationary sound is not needed (with Syn-LL localisation not so easy)

Syn = Syn-LL1,3s

Standard deviation ICE smaller than Syn / Syn-LL

Nearly no difference between Syn-LL (1,24 s) and / Syn (1,31 s)

Vehicle exterior noise …3. Slowing vehicle Cross-walk

1. ICEV stopped with idle (Diesel) „V-LL“2. ICEV stopped without idle (Start/Stop Diesel) „V-MS“3. EV stopped without Sound „E-FZ“

5 different sounds:

4. EV Synth. stopped with idle-Sound „Syn-LL“

5. EV Synth. stopped without idle-Sound „Syn“Synthetic with idle-sound

Synthetic with-out idle-sound

EV without deccelaration-sound causes risks (big deviation)

Nearly no difference between Diesel with/without Start/Stop

Conclusion: Stationary sound gives no advantage in recognition of EV/HEV

Results:

Not heard anymoreWaiting for change

Nearly no difference between Syn-LL (+0,6 s) & Syn (+0,55 s)

Vehicle brakes?Vehicle accelerates?

Vehicle exterior noise …Operation Status: acceleration – braking?

Best recognition with fewest failures ?

Sound sweeps (2 s) with Frequency alteration rateof 10%, 20%, 40%, 80%, 160% and 320% with and without backround noise of 55 dB(A)

without backround noise brakingwith backround noise braking

without backround noise accelerationwith backround noise acceleration

Frequency between 250 Hz and 400 Hz = 80% freqeuncy alteration

Vehicle exterior noise …Study Conclusions:

Additional Sound is needed for detection of pre comming / approching EVs/HEVs

Only a few individual bands of 1/3-octave have to be higher than backround noise bands

Frequencies should be simular to deep-frequent ICE signals

There is no correlation between recognition time and sound level

Approaching (parking lot) & slowing (cross-walk) of EV/HEV without sound can‘t be recognised (early enough)

Stationary Sound isn‘t necessary for Approaching (parking lot) & slowing (cross-walk) of EV/HEV

Facceleration and braking should be shown by freqeuncy alteration between 250 - 400 Hz

Thank you

Vehicle exterior noise different traffic situations /operating conditions