Horn Characterization
- Jonathan Xie
The following two horns were tested in the bay with a power supply:
Horn | Current at 12V | Current at 15V | Notes |
|---|---|---|---|
 ‘Black Horn’ FIAMM 72112 Freeway Blaster Horn | 4.36 A | 5.34 A | 15V was higher pitch and significantly louder (qualitatively observed) than at 12V |
 ‘Red Horn’ (no part number) | 3.00 A | 3.98 A | 15V was higher pitch than 12V, but only a slight increase in perceived volume |
By regulations, the horn must produce at least 75dB at 15m away, for 5 minutes continuously:
Horn | Voltage | Distance | Configuration | dB |
|---|---|---|---|---|
Red Horn | 12V | ~11m | Horn not obstructed, facing towards the decibel reader | 97 |
Red Horn | 12V | ~11m | Horn covered by 2 cones, facing towards the decibel reader | 85 |
Red Horn | 12V | ~11m | Horn covered by 2 cones, facing sideways from the decibel reader | 85 |
Conclusion:
Red horn draws less power than the black horn, and is preferable to use, if it passes regs:
Red horn with no obstruction will most likely be sufficient for regs (>75dB @11m)
Need to test if red horn (at 12V for worst-case) will still work if obstructed by a layer of carbon fibre (to reduce mechanical design complexity)
If the above fails, then use black horn