1. Alarm Types and Testing

2. Alarm Types Fixed Outputs: Type Normal High Low Other Pause A ●
As required
OEM / Fleet option B C D

3. SPLs Fixed Outputs Tonal: Type Normal High Low S = As Standard 68 – 78
85-95
50 – 58
+ [5] dBA ꓮ
+[10] dBA B
+ X dBA C B S A C

4. Switched by time or driver or ….
SPLs
Outputs Types Tonal:
Type
Normal
High
Low
Per Standard
68 – 78
85-95
50 – 58
Manual
Switched by time or driver or ….
Self-Adjusting
Stepped
Continuous

5. Self-Adjusting Speaker acting as mic registering overall dBA
Mic able to filter ambient by:
Frequency range
Impact sounds less than [300] m/s ignored ??

6. Alarm Types Need to define where alarm steps.
Graph shows steps at lower and upper limits currently in draft.
Difference compared to self-adjusting:
Lower step = 10 dBA
Higher step = 8 dBA

7. or 72 to 74 +/- 4dBA or 71 to 75 +/- 3dBA
Testing
Laboratory / Component Supplier:
Type
Normal
High
Low
Per Standard
73 +/- 5 dBA
or 72 to 74 +/- 4dBA or 71 to 75 +/- 3dBA
or 70 to 76 +/- 2dBA
90 +/- 5 dBA
ditto
54 +/- 4 dBA
Ditto
Manual
Self-Adjusting
Stepped
As above [+ 5 dB(A) ± 4] in addition to the ambient sound in the range of [63 to 100] dB(A)
Self-Adjusting Continuous
Current SAE J994 allows max of +/- 4 dBA variation from alarm rated value

8. Where is ambient measured?
Assumed at alarm:
Alarm installed at the rear most point of vehicle
Measuring ambient at rear
Alarm installed within the vehicle:
Ambient could be quieter; external sounds masked
Ambient could be louder:
from resonance by truck/vehicle body or
other sounds from vehicle

9. Audibility – ISO 7731
Where is most frequency content in ambient sound?
An alarm can often have a lower overall dBA value than ambient and easily be detectable

10. OEM / Distributor / Fleet On Vehicle Testing
Fixed Outputs Tonal:
Alarm selected based on installation position to ensure sufficient sound is projected to the area of risk.
Type
Normal
High
Low
S = As Standard
68 – 78
85-95
50 – 58
+ 5 dBA ꓮ
+10 dBA B
+ X dBA C B S A C
Illustrative examples / values

11. Tonal v Broadband Sound Fields

12. Loudness v Audibility
Alarm A at 1.5kHz will seem twice as loud at Alarm C!