Here given is a circuit in which the status of the output pins of a Flip Flop IC can be toggled by using sound. A condenser microphone is used for picking up the sound. The first two op-amps in the IC1 LM 324 is used to amplify the sound picked by the condenser microphone. The third op-amp inside LM 324 is wired as a level detector. When ever the voltage produced due to sound have a level more than that of the reference voltage at pin 5 of the third op-amp, its output (pin 7) goes high, triggering the flip flop IC1 CD 4027.As a result the state of the output pins of CD 4027 ( pin 1 & pin 2) toggles for each burst of sound.

Circuit diagram with Parts list.



  • Assemble the circuit on a good quality PCB.
  • The circuit can be powered from three 1.5 V cells in series.
  • The ICs must be mounted on holders.
  • All capacitors must be rated 10V.
  • The mic M1 is a condenser mic.
  • The sensitivity of the circuit can be adjusted by varying the preset R9.


  1. Prasenjit roy

    What will be the output of Q and Q(bar)

  2. how many leds can hold and how should be connected

  3. Can I get the project report of this project.I am interested in doing this project

  4. Nirmal kumar

    this will hold output the value for next sound ….?

  5. thanks for ur cooperation and encouragements i’ll
    very happy about this site thanks