This circuit is a double tone Police sound and Single tone old ambulance sound. This circuit is usually installed on a on battery powered cars, motorcycles, and bicycles for fun kid not only that, this circuit also used in models and other games.
The oscillation of IC1A and IC1B gates produces the typical dual tone sound of Fire-brigade or Police cars if SW1 positioned as shown in the circuit diagram. Pushing on P1 that starts oscillation in IC1C and IC1D causes the old siren sound increasing in frequency and then slowly decreasing if SW1 in the other position. To obtain a more realistic and louder output, we use the loudspeaker that has a reasonable dimension and well wrapped. The values of C1, C2, C5, C6 and/or associated resistors will affect the tone and period of the sound oscillations. This circuit does not have power switch: leave SW1 in the low position (old-type siren) and the circuit consumption will be negligible. [Circuit schematic diagram source: english.cxem.net]