Here is a very simple Kojak siren that is built with two 555 timer ICs and has 2 linear potentiometers that allows the control of sound speed and tone.
IC2 produces a sound that can be adjusted with P2 and then drives a small speaker.
The amplitude of the signal is modulated by IC1 with a low frequency signal.
The modulation speed can be adjusted with P1.
By using both potentiometers you can obtain a siren that produces a sound that is similar to the american police cars. The entire circuit is small enough to be constructed inside a small box together with the battery and speaker. You can use a 8Ω speaker in series with a 47Ω resistor instead of the 150Ω one. You can use it as a doorbell too.