1

Defining Sounder Criteria

Presented by Henry Morgan

Edited from paper prepared and presented by Prof. Geoff Leventhall to ISO Apr 2011

Acoustical Consultant

geoff@activenoise.co.uk

Sounds for Electric Vehicles

QRTV-06-09

2

What Should a Sounder for Quite

Cars Achieve? Safety:

Audibility, Locatability, Directivity

Environmental: Acceptability, Directivity, Attenuation

3

AudibilityDepends on loudness (phons) or sound pressure level (dBA) compared with background noise

Why phons? Tests show that, for equal dBA, broadband sounds are louder than tonal sounds.

4

ALARM SOUND

LAeq dBA

Loudness Phon

Broad band

92.3 103.2

Complex

1450Hz

92.1 98.5

Loudness of broadband and tonal back alarms

5

Depends on ratio source diameter to wavelength For 0.1m source,

D/lambda = 0.25 at 850HzD/lambda = 1 at 3400Hz

Directional radiation from a piston source

6

A-Weighted Directivity

Prius Hybrid fitted with Brigade broad band prototype sounder

7

Limit the directionality

8

Broadband Sound

• Broadband sound contains complete auditory information for location

• Greater higher frequency content gives:

greater directivity

greater attenuation

9

Equal loudness contours

range of added sound

10

White soundWhite

-50

-45

-40

-35

-30

-25

-20

-15

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rel

ativ

e le

vel d

B

11

Pink SoundPink

-50

-45

-40

-35

-30

-25

-20

-15

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rela

tive

leve

l dB

12

Band Limited SoundBand limited

-80

-70

-60

-50

-40

-30

-20

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rel

ativ

e le

vel d

B

13

500Hz to 3500Hz

500Hz to 3500Hz

-30

-25

-20

-15

-10

-5

0

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Frequency Hz

Re

lati

ve

lev

el d

B

14

A back alarm soundBB reversing alarm

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rel

ativ

e le

vel d

B

15

Multiple tone soundTones

-80

-70

-60

-50

-40

-30

-20

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rel

ativ

e le

vel

dB

16

Pink Broadband sound for EVs

Car sound

-50

-45

-40

-35

-30

-25

-20

-15

-10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Frequency Hz

Rela

tive level d

B

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All the sounds

White

Pink

Band limited 1

band limited 2

Back alarm

Multiple tone

Pink BB for EVs