Quiet Challenges for Vehicle Safety

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1 Page 1 Quiet Cars@BMW. Challenges for Vehicle Safety and Acoustics. Alfred Zeitler, Robert Liebing, Armin Gräter & Jan Urbahn Research & Innovation Center, Munich BMW of North America, LLC

2 Page 2 Introduction. Basic Attitudes and Strategic Statements. Corporate values of BMW are based on sustainability and social responsibility Need for specific safety measures for EVs and HEVs has been acknowledged for a long time Research into evaluation methods has been performed in alliance with Daimler, Porsche and the Technical University of Munich Acoustical warning devices are currently being developed for all EVs and HEVs at BMW BMW has a supportive attitude towards research and development of non-acoustical approaches as well Note: not only pedestrians but also drivers will benefit from warning function (stress reduction)

3 Page 3 Introduction. BMW Approach and Responsibilities. Vehicle Safety Psychoacoustics Technical University of Munich Sound Design & Engineering Interdisciplinary team of safety specialists, acoustical engineers, sounddesigners & psychologists (Bavarian Assoc. of Blind & Visually Impaired People)

4 Page 4 Introduction. BMW Approach and Responsibilities. Vehicle Safety Psychoacoustics Technical University of Munich Sound Design & Engineering Interdisciplinary team of safety specialists, acoustical engineers, sounddesigners & psychologists (Bavarian Assoc. of Blind & Visually Impaired People)

5 Page 5 Vehicle Safety. Risk Assessment. Exploration of safety-relevant traffic scenarios Definition and priorization of situations Top Critical Situations at v = 0-19 mph (0-30 km/h) stop & go, turning, green traffic light without acoustic signal public car parks (buildings) Most Critical Driving State Risk Level driving at constant speed 6 accelerating (and driving at constant speed) starting into the traffic after a stop on the lane accelerating 4 driving behind very slow and big vehicles (optically and acoustically covered) driving at constant speed 4 private car park / close to street accelerating 3 accident situation driving at constant speed 3 public car parks (open area) driving at constant speed 2 driving behind slow but small vehicles (visible, but acoustically covered) driving at constant speed 2 obstacle on lane (vehicle, bus, ) accelerating 2 6

6 Page 6 BMW Approach and Responsibilities. Psychoacoustics. Vehicle Safety Psychoacoustics Technical University of Munich Sound Design & Engineering Interdisciplinary team of safety specialists, acoustical engineers, sounddesigners & psychologists (Bavarian Assoc. of Blind & Visually Impaired People)

7 Page 7 Psychoacoustics. Requirements for Exerior Noises of EVs. Requirements Perceptibility Pleasantness Identifiability Dynamic Information Localisation Description Vehicle noise can be detected in background noise in a safe distance Avoids annoyance at least and creates esthetic value at best Noise is recognized as a vehicle Vehicle speed and acceleration/slowing is being conveyed Position of vehicle can be perceived easily

8 Page 8 Psychoacoustics. Assessment of Perceptibility (Kerber, 2008). Calculation of Perception Distances. Vehicle Speed Time varying sound-pressure of masker Time varying sound-pressure of vehicle Calculation of masked thresholds according to Fastl & Zwicker (2007) Perception-distance Adapted from:kerber (2008).

9 Page 9 Psychoacoustics. Algorithmic Prediction of Perceptibility. Perceived in sufficient time Collision Masking level 62 db(a) 57 db(a) 52 db(a) v=10km/h (6 mph) 47 db(a) Electric Vehicle 25 m (82 ft) 20 m (66 ft) 15 m (49 ft) 10 m (33 ft) Distance at perception 5 m (16 ft) pedestrian Hybrid E-Mode Hybrid ICE-Mode ICE Vehicle

10 Page 10 Psychoacoustics. Sound Level db(a) vs. Perceptibility. Maskers at 55 db(a) Urban Traffic Urban Babble Pink Noise Per rceptibility [db] S-03 S-11 S-13 S-17 S-18 G-01 G-02 G-03 D-11 D-16 S-03 S-11 S-13 S-17 S-18 G-01 G-02 G-03 D-11 D-16 S-03 S-11 S-13 S-17 S-18 G-01 G-02 G-03 D-11 D-16 Sounds for EVs Gasoline Diesel Sounds for EVs Gasoline Diesel All Vehicle noises at 62 db(a) Sounds for EVs Gasoline Diesel Perceptibility mainly depends on masking properties of the background noise level and character of the vehicle sound => Sound level db(a) is not sufficient for evaluation or prediction

11 Page 11 BMW Approach and Responsibilities. Sounddesign & Soundengineering. Vehicle Safety Psychoacoustics Technical University of Munich Sound Design & Engineering Interdisciplinary team of safety specialists, acoustical engineers, sounddesigners & psychologists (Bavarian Assoc. of Blind & Visually Impaired People)

12 Page 12 Challenges for Acoustics. Identifiablity of Electric Vehicles.? EVs should shave a distinguishable sound because many of their properties including dynamic performance are different.

13 Page 13 Challenges for Acoustics. Field Study with Blind Community. Participants: 5 members of the Bavarian Association of Blind and Visually Challenged people Location: vincinity of Munich Vehicles/sounds: Original exterior noise of MINI E 8 synthetically-produced sounds ICE Vehicle (4-cyl. gas. engine) Vehicles passing by at a constant speed of 10 mp/h

noise not suitable for EVs un-suitable very suitable ICE noise is less Affectivity surprising and

14 Page 14 Challenges for Acoustics. Field Study with Blind Community. Suitability MINI E Synthetic Sounds very threatening ICE Vehicle MINI E Original Noise very friendly ICE noise not suitable for EVs un-suitable very suitable ICE noise is less Affectivity surprising and therefore may initially appear less threatening due to familiarity However, a quick learning effect is expected Goal: EV to sound more pleasant than ICE

15 Page 15 Challenges for Acoustics. Requirements for Exerior Noises of EVs. Requirements Perceptibility Pleasantness Description Vehicle noise can be detected in background noise in a safe distance Avoids annoyance at least and creates esthetic value at best Sound Character Identifiability Dynamic Information Localisation Noise is recognized as a vehicle Vehicle speed and acceleration/slowing is being conveyed Position of vehicle can be perceived easily Level shift Pitch shift component Attention Catcher

16 Page 16 Challenges for Acoustics. Perceptible and Pleasant Sound Character with Level Shift. Loudness Perceptible & pleasant sound character Level shift Speed [mph] Sounddesign with enhanced perceptibility Speed-dependent increase of level up to 16 mph (25 km/h) Pronunciation of load change through sound level Fade out from 16 mph (25 km/h) Pitch shift component Attention Catcher

17 Page 17 Challenges for Acoustics. Pitch Shift Reflecting Vehicle Dynamics. Loudness tonal components Perceptible & pleasant sound character Level shift Speed [mph] Speed-dependent variation of tonal components Frequency range according to hearing sensitivity Slope of pitch shift to match subjective impression of acceleration (under investigation) Pitch shift component Attention Catcher

18 Page 18 Challenges for Acoustics. Attention Catcher for Alerting against Departure. Loudness Attention catcher tonal components Perceptible & pleasant sound character Level shift Speed [mph] Rapid boost of sound level on departure Immediate attenuation by analogy to a start-up sound of ICE vehicles No idle noise needed Pitch shift component Attention Catcher

19 Page 19 Challenges for Acoustics. Recommendation. Loudness Attention catcher tonal components Perceptible & pleasant sound character Level shift Speed [mph] Enhancing safety with an environmentally friendly sound with esthetic value. Pitch shift component Attention Catcher

20 Page 20 Thank You for Your Attention.

Sound detection of electric vehicles by blind or visually impaired persons

Sound detection of electric vehicles by blind or visually impaired persons Dr. Klaus-Peter Glaeser Torsten Marx Dr. Eike Schmidt Federal Highway Research Institute (BASt) Bundesanstalt für Straßenwesen