When I connect a piezo buzzer to my Arduino Duemilanove (see attachment!), it makes a weak and strange sound when the I/O pin is set to LOW (measured 0,01 V / 0,02 V with a multimeter). When I disconnect the buzzer from the I/O pin or disconnect the Arduino from the power source the sound stops. Even when I play a tone on the buzzer using the tone() function, I still hear this sound (even though it is very weak compared to the tone). I am using digital I/O pin 4 and a frequency of 2048 Hz (rated frequency, see data sheet!).
Data sheet: http://www.sparkfun.com/datasheets/Components/CEM-1203.pdf
There is a schematic in the datasheet with a transistor, but I am not sure if this will solve anything.
Please let me know! Is 0,01 V / 0,02 V too much?
Thanks! I really appreciate your help!