Max signal is 0.5V above VCC.
So 5V would be a no-no on a 3.3V powered part.
Take the signal and divide it in half with 2 10K resistors:
Signal - resistor R1 - arduino pin - resistor R2 - Gnd.
Or select resistors so that the signal remains below 3.3V
Vout = Vin * R2/(R1 + R2)
3.3V = 5V * (10,000)/(R1 + 10,000)
3.3V * R1 + 3.3V*10,000 = 5V * 10,000
3.3V * R1 = (50,000 - 33,000)
R1 = 17,000/3.3 = 5.15K
So use 10K & 5.7K:
5V*10,000/(10,000 + 5700) = 3.185V