When I started playing with circuits I had 2 different speakers. The first was from a phone and the other was a piezo speaker. When you supply 5V to a speaker it just gives a thud and when you connect and diconnect it quickly you get pulses. When I connected a piezo speaker it gave a frequency not a thud. I then bought a Piezoelectric ultrasonic transducer that I hoped would give a mist effect but disappointingly I got nothing . Would I need some form of pulse to the device to get it to work?