The difference between speaker and buzzer
Buzzer and speaker are the acoustic components that can generate sound, if you just need sound to warn or remind, both of them are fine.
We divide buzzer into piezo and magnetic buzzer. There are some differences in power consumption, dimension, frequency and drive method between piezo and magnetic buzzer, however, both of them basically pull the SPL to the highest at a certain frequent point in order to generate as high SPL as possible in the small size. The SPL will be very low if it is not at the resonance point, even 20dB difference. By the way, the sound of buzzer is drove by square waves; therefore it is harsh to the human ears.
Micro speaker is drove by the sine waves, to compare with buzzer, the sound is much more comfortable for us. However, the bandwidth is wider, and the frequency is lower, therefore, the micro speaker’s SPL must be lower than the buzzer with the same size, and also need enclosure to help the low frequency, otherwise the sound will be very small.