Reduce voltage to read buzzer with GPIO
Use a resistor from the buzzer, maybe 1kohm to 10kohm and feed it to a zener diode. The zener will limit  the voltage seen by your chip. If your circuit runs from 3.3 volts choose a 2.7 volt zener diode. If it runs from 5volts choose a 4.7volt zener.

Try googling zener voltage regulator.