If I connect this little mechanical buzzer to a 3V supply, then hold my AM radio close to it with the radio tuned so I can't hear any stations, I can hear the buzzer on the radio. If I turn up the radio volume, the buzzer is amplified much louder over the radio than what I can hear just from the buzzer. I tried connecting a little piezo buzzer instead of the mechanical buzzer but I couldn't hear the piezo buzzer on the radio.

Why is the mechanical buzzer sound transmitted to the AM radio?