Acoustic Vehicle Alert Systems [AVAS] for EVs

A: Principle: Free-field SPL decays by 6 dB for each doubling of distance. Applied here, doubling from 1 m to 2 m yields 62 minus 6, landing at 56 dB(A). Distractor C catches engineers who remember inverse-square law but double-count it in logarithmic units.

A: Principle: Fatigue damage scales with total load cycles, estimated from frequency and time. Applied here, 30 Hz × (8 h/week × 3600 s/h) × ~200 weeks lands near 4×10^7 cycles. Distractor D tempts engineers who forget to convert hours to seconds.

A: Principle: Material pairing should minimize galvanic potential and coating breakdown. Applied here, Zn-Ni plated steel is sacrificial and compatible with e-coated steel in splash zones. Distractor B traps those who overgeneralize stainless as corrosion-proof, ignoring galvanic mismatch.

A: Principle: Safety margins reduce the allowable threshold to cover sensor error. Applied here, 20 km/h divided by (1.03 × 1.2) lands near 16.2 km/h. Distractor B catches engineers who apply error but drop the DFMEA safety factor.

A: Principle: Acoustic power relates logarithmically to SPL relative to 10⁻¹² W. Applied here, 60 dB corresponds to 10⁻⁶ W referenced over area, yielding milliwatt-scale power. Distractor C tempts those who forget the area term at 1 m.

A: Principle: Material selection follows the most aggressive environmental exposure. Applied here, EPDM resists water and ozone, avoiding hydrolysis seen in polyester urethanes. Distractor D catches engineers focused on temperature, not moisture-driven aging.

A: Principle: Differential strain equals ΔCTE × length × ΔT. Applied here, (90−23)×10⁻⁶ × 40 mm × 80 K gives roughly 0.21 mm. Distractor B traps engineers who forget to apply the temperature swing.

A: Principle: Temperature rise scales with dissipated power and thermal resistance. Applied here, ~4.5 W lost in a semi-enclosed volume yields tens of degrees, not single digits. Distractor C attracts those who ignore even modest convective cooling.

A: Principle: With linear damage, cycles scale with frequency and time. Applied here, 200 h at 50 Hz equals fewer field-equivalent cycles when normalized to 30 Hz, landing near 33,000 km. Distractor C catches engineers who scale frequency in the wrong direction.