Positive and Negative Polarity of Buzzer

Passive buzzers don't differentiate positive and negative polarity while active buzzers do. There is a little similarity between passive buzzers 

and horn.When we load electric signal with different frequences on its two pin feet,then it can make sound.And we can make different sounds by changing

the frequences. As for active buzzers which have positive and negative polarity,they can make sound when voltage signal is effected on the pin feet.

However,active buzzers are with single tone and constant frequency.