We are going to make a Police Siren Circuit using two 555 timer IC. The circuit will produce an up-down wailing sound from the speaker. We will be using two 555 timer IC, so the circuit will be bit complex to make. We will fire first 555 is wired as a low frequency oscillator to control the voltage control pin 5 of the second 555. The voltage shift on pin 5 makes the frequency of the second oscillator to rise and fall. I will explain each step in detail with step wise execution and instructions of the circuit.”

Link